© 2000 by The Society for Integrative and Comparative Biology
Abstracts by Author
62.2 ABGRALL, M-J.*, WALTERS, L.J., University of Central Florida, Orlando. Settlement preferences and recruitment of the bryozoan Bugula neritina on drift macroalgae in Mosquito Lagoon, Florida.In Mosquito Lagoon (the northernmost region of the Indian River Lagoon, Florida), significant differences in the abundance and diversity of drift macroalgae were found when sampled on a monthly basis from January 1998 - March 2000. In the winter months, the arborescent bryozoan Bugula neritina was commonly found attached to available drift species in the order Gigartinales, Rhodophycea. However, it was rarely found on these same algal species when they were attached. In replicated single and multiplechoice trials in the laboratory that included the seagrass Halodule wrightii and the macroalgae Hypnea cervicornis, Gracilaria armata, Gracilaria tikvahiae, Enteromorpha compressa, Agardhiella subulata and Dasya rigidula, the two species of red algae Gracilaria were significantly preferred in both types of trials. Despite having a similar morphology to G. armata, Dasya rigidula was avoided by settling larvae of B. neritina and greater than 60% larval mortality occurred in the bioassays.To determine if the preferred settlement choice of B. neritina is due to the morphology of Gracilaria or secondary chemicals, field trials were run comparing recruitment on attached versus drift G. armata and attached versus drift mimics. Bugula neritina never recruited on attached G. armata and rarely on mimics (drift or attached); however, large numbers of larvae recruited on drift G. armata.
P2.21 ADAMS, J.A.*, MOORE, P.A., Bowling Green State University, Bowling Green, OH. Attraction of conspecifics to molt signals in crayfish.
For many organisms olfaction plays a key role in communication. Crayfish use olfactory signals to find mates, warn of predators, and relay social status. While many of these situations have been studied in detail, behavior of conspecifics toward molted individualshas not. The physiology of crayfish changes dramatically during molting (ecdysis), which in turn changes both the content and concentrations of the chemical cues released into the water. We hypothesized that conspecifics would pick up these changes in chemicals released and move toward the molt signal. A Y-maze was used to test for a differential attraction to various odors presented to intermolt (non-molting) crayfish. All crayfish used were of the species Orconectes rusticus. The odor sources were molt crayfish, intermolt crayfish, aged tank water (control), or food (fish carrion). Variables measured included initial arm choice, time spent in each arm, walking speed toward source, meral spread, and straightness of path. On average, crayfish spent more time the presence of molt signals when paired with intermolt or control stimuli. The food stimulus was more attractive than over any of the other stimuli. These results demonstrate that there is a difference in the way a conspecific perceives a recently molted individual versus an intermolt individual. Since cannabalism and aggressiveness toward molted individuals has been observed in laboratory situations, the ability of a conspecific to recognize a molted individual by olfaction has implications for both social interactions and survival of individuals in crayfish populations.
68.1 ADELMAN, L.M., Institute for Learning Innovation, Annapolis, MD. Integration of research and education: Are you ready?
Have you seen the new NSF guidelines? "One of the principal strategies in support of NSF's goals is to foster integration of research and education through the programs, projects, and activities it supports at academic and research institutions....NSF is committed to this principle of diversity and deems it central to the programs, projects, and activities it considers and supports." The subtext is that NSF, as well as other funding sources and professionals worldwide, are embracing the tremendous value, benefit, and responsibility of the scientific community to facilitate the utilization of their research, resources, and expertise in educational outreach! This talk will explore the benefits and challenges of scientists involvement in public education, with particular emphasis on identifying and exploring existing community outreach needs, effective strategies, and partnerships.
S3.5 AERTS, P.*, VAN DAMME, J., HERREL, A., University of Antwerp (UIA), Belgium. Intrinsic mechanics and control of fast cranio-cervical movements in aquatic feeding turtles.
Aquatic feeding strikes on agile prey in snake-necked turtles involves fast neck extension, bucco-pharyngo-oesophageal expansion and head retraction. The ultimate, rectilinear acceleration of the head towards the prey requires complex vertebral rotations, largely differing from strike to strike. This poses serious control-demands to the numerous intrinsic neck-muscles which are the sole neck extensors. Mathematical modelling shows, however, that extensor activity might be redundant for this phase of the strike. The ultimate head acceleration always goes along with forceful bucco-pharyngeal expansion. The momentum of the thus induced suction flow suffices to pull the head (and the neck) straight towards the prey. The global control of this buccal expansion proceeds identically to what is observed in primary aquatic feeders : through a rostro-caudal expansion sequence characterized by an optimal timing of the functional components supporting the expansion wave. Yet, distinct structural solutions, both at the skeletal and muscular level, are involved. This points towards prominent hydrodynamic constraints. Extrinsic neck muscles retract the head and neck. Given the high number of degrees of freedom, this musculo-skeletal system is obviously underdetermined which compromises control. Erroneous neck folding might be avoided through the presence of a subtle click system at the level of the joint between cervical 5 and 6.
24.4 AHN, A.N., University of California, Berkeley, CA. Using in vivo stimulation and strain conditions to explain how two muscles function differently under identical conditions.
Even when experiencing identical strain and stimulation conditions, two leg muscles of the cockroach, Blaberus discoidalis, function differently. Both muscles are innervated by the same, single excitatory motor neuron, extend a single degree-of-freedom joint, and have similar twitch kinetics and similar force-length and force-velocity properties when maximally stimulated. When both muscles were strained cyclically and stimulated phasically under identical conditions (8 Hz; 15% strain; in vivo stimulation pattern determined during running), muscle 178 generated mechanical energy over a cycle (10.1 W kg–1; n = 5), while muscle 179 absorbed net mechanical energy (–14.7 W kg–1; n = 6). Forces generated during shortening determined the main difference in mechanical function between the two muscles. Although the force-length relationships of muscles 178 and 179 were similar when maximally stimulated, the force-length relationships when submaximally stimulated showed that muscle 178 generated higher forces at shorter lengths than muscle 179. Differences between the two muscles in their submaximal force-length relationships and in force enhancement after a passive stretch could account for approximately 85% of the difference in peak force generated between the two muscles during oscillatory contractions. Using the in vivo conditions and examining the history-dependent properties of these muscles provide clues to how the muscles function differently under identical cyclical conditions. Understanding the functional consequences of submaximal stimulation and contraction history can reveal differences in force generation that are not apparent during maximally stimulated muscle in isometric and isotonic measurements.
S11.12 ALEXANDER, R.McN., University of Leeds, England. Stability and manoeuvrability of terrestrial vertebrates.
For a standing animal to be statically stable, a vertical line through its centre of mass must pass through the polygon of support defined by its feet. Statically stable gaits are possible for quadrupeds but do not seem to be used; a discussion of turtles shows why they may be disadvantageous. Physical and mathematical models have shown that passive bipedal walking machines can be dynamically stable for motion in the sagittal plane, but not in roll. Accelerations and decelerations of animals may be limited by muscle strength, by the coefficient of friction with the ground, or by considerations of stability. Cornering ability similarly may be limited by strength or by the coefficient of friction. A simple mathematical model shows that it may be faster to use a longer route with corners of larger radius,than a shorter one with sharper corners. The concepts of oversteer and understeer,as applied to wheeled vehicles, may throw light on the stability of running.
S3.1 ALFARO, M.E.*, JANOVETZ, J., BLOB, R., WESTNEAT, M.W., Field Museum, Chicago. Biting in teleost fishes.
Biting is a distinct means of feeding in fishes in which upper and lower jaws forcibly grasp, tear, or cut the prey. Biting is a common mode of feeding in many groups of fishes, including parrotfishes, wrasses, cichlids, triggerfishes, surgeonfishes, damselfishes, and characins, yet the kinematics and motor patterns of this behavior have received relatively little attention compared to suction feeding. To quantify the muscular motor pattern of biting and to identify aspects of it that appear to be phylogenetically conserved, we recorded activity from the epaxialis, levator operculi, sternohyoideus, and subdivisions of the adductor mandibulae during the bite in species of parrotfishes, wrasses, and serrasalminae. In parrotfishes, significant species-level differences were found in the duration and timing of muscle activity, suggesting that the motor control of biting is evolutionarily plastic at relatively low phylogenetic levels. To determine if biting motor patterns differ significantly from suction feeding motor patterns, we used MANOVA and principal components analysis to compare EMGs of biting and suction-feeding taxa. The multivariate space occupied by biting and suction feeding is constrained by the motor control requirement of opening and then closing the jaws. However, biting in parrotfishes was significantly different than suction feeding in other teleosts, although there was a high degree of overlap among all feeding strikes. Many biters also showed little or no epaxialis activity, suggesting that, in contrast to suction feeding, cranial elevation is relatively unimportant in biting. ONR N000149910184 and NSF DEB- 9815614.
P2.37 ALKINDI, A.Y.A., MAHMOUD, I.Y., ALGHEILANI, H.M.H., AL-HABSI, A.A., ALKIYUMI, A.A., KHAN, H.*, Sultan Qaboos University, Oman, Sultan Qaboos University, Oman, Ministry of Agri. & Fish., Oman, Sultan Qaboos University, Oman, Ministry of Reg. Municip. & Environ., Oman, Sultan Qaboos University, Oman. The degree of crowding and its effect on the nesting behavior in the green turtle Chelonia mydas in Oman.
The nesting behavior of the green turtle, Chelonia mydas, was observed during high population density period (June–October) and low population density period (Nov–May) in Ras Al-Hadd, Sultanate of Oman. Oman hosts one of the largest nesting populations in the world. The degree of crowding during the nesting season reveal some information on the way the turtles "adjust" to the seasonal changes to some ecological factors such as the availability of nest sites, and the location of the nests relative to the tidal zone. During low density, the turtles tend to build their nest away from the tidal zone and the frequency of nesting near or inside the tidal zone is low. During high density, the frequency of choosing the nests near or inside the tidal zone increases significantly even when there is less crowding and more nesting areas are available in a giving night. Based on these conditions, we suggest that the turtles become aware of the crowding condition before they ascend on the beaches as they gather near the nesting grounds. The significant of such nesting strategy will be discussed.
34.5 ALTSHULER, D.L.*, CHAI, P., University of Texas at Austin. Hovering performance of hummingbirds in hyperoxic gas mixtures.
We present a test of the hypothesis that inspiration of hyperoxic air increases hummingbird hovering performance when birds are challenged aerodynamically. We measured the maximum duration of hovering flight and the simultaneous oxygen consumption of ruby-throated hummingbirds (Archilochus colubris) in low density heliox that was either normoxic (21% O2) or hyperoxic (35% O2). As density decreased, hummingbirds in hyperoxia significantly increased hovering duration, down to the density at which birds could no longer sustain hovering flight. At this final density, skeletal muscle activity appears to be anaerobic and independent of oxygen concentration. Hummingbirds in hyperoxia showed no significant increase in oxygen consumption at lower densities. Additionally, we tested the birds ability to discriminate between artificial flowers infused with either normoxic or hyperoxic gases. Even after a full day of training birds failed to associate oxygen concentration with a particular flower, independent of air density. Supplemental oxygen thus yields increased hovering duration but the minimum density at which birds can fly is limited exclusively by aerodynamic considerations.
69.1 AMUNDSON, R., University of Hawaii at Hilo. Evo versus devo: methodological conflicts in the treatment of variation.
Evolutionary and developmental biology were independent enterprises for most of the twentieth century. Differences in goals led to differences and even inconsistencies in methodologies and practices. One of the tasks of an integrative program of evolutionary developmental biology will be to negotiate these inconsistencies. Among the most difficult may be conflicts in the ways variation is dealt with. For example, the evolutionary antagonism towards typology may be irreconcilable with such organizational developmental concepts as the Bauplan. Is it possible to be a population thinker while simultaneously conceiving of evolution as changes in developmental processes?
24.2 ANDERSON, B. D.*, FULL, R.J., GARCIA, M., University of California, Berkeley, CA. A spring-mass model of centipede locomotion.
The laterally undulating Arizona centipede, Scolopendra heros, uses a metachronal gait in which all legs on the concave side of the bent body touch the ground at a single point. Each leg of the wave of legs traveling through this point is not on the ground for a long enough period to aid in understanding centipede locomotor dynamics. However, as a wave of legs travels through this one point of ground contact, the individual legs combine to generate ground reaction forces (GRFs) and mechanical energies (MEs) of the center of mass that are similar to a spring. This is analogous to the spring-like behavior of all legs in contact with the ground at a time, or the "virtual leg," in symmetrical gaits. We model each wave of centipede legs as a "virtual wave-spring." Centipedes have several points of leg contact, or virtual wave-springs, on the ground generating force at any given time. Therefore, we modeled centipede whole-body locomotor dynamics as the sum of several virtual wave-springs. The period of each virtual wave-spring and the lag between successive virtual wave-springs were altered to model different kinematic conditions. Our model predicts that only under unobserved kinematic conditions would centipedes demonstrate whole-body dynamics of a rolling wheel, as predicted by Gray (1953), or have whole-body GRF and ME patterns that complete a full cycle in a typicallyñdefined stride period. The model predicts that under most conditions, the whole-body GRF and ME patterns will complete a full cycle in the period it takes for a wave of legs to complete its contact with the ground and the next wave of legs to be set on the ground. The period of time a wave of centipede legs is on the ground is analogous to the stride period in symmetrical gaits.
P2.48 ANDERSON, C. W., Idaho State University, Pocatello, ID. Anatomical evidence for brainstem circuits mediating hypoglossal motor output in the leopard frog, Rana pipiens.
Using injections of fluorescein dextran amine (FDA) combined with activity-dependent uptake of sulforhodamine 101 (SR101), brainstem circuits presumed to be involved in hypoglossal motor output were investigated. Injections into the cerebellar cortex combined with retrograde labeling of the peripheral hypoglossal nerve demonstrate convergence at the level of the medial reticular formation. This convergence suggests an integrative region for afferent feedback from the hypoglossal nerve and information through the Purkinje cell layer of the cerebellar cortex. Injections of FDA into the cerebellar nuclei also demonstrate a bilateral efferent projection to the hypoglossal motor neurons. The SR101 data suggest a reciprocal pathway between the medulla and the trigeminal nuclei. This pathway was identified through peripheral hypoglossal stimulation while SR101 was bath applied to a semi-intact brainstem preparation. Additionally, the SR101 uptake clearly labeled the ventrolateral hypoglossal nuclei, the medial reticular formation and the Purkinje cell layer of the cerebellar cortex. The trigeminal nuclei coordinate the motor output of the levator mandibulae complex, the mouth closing muscles, and this pathway may provide a mechanism for coordinating tongue movements (through hypoglossal nuclei) with jaw movements during feeding. Taken together, these data provide additional insight for understanding the neurophysiological pathways used to coordinate the proper timing of feeding motor output in anurans.
1.3 ANDERSON, E.J.*, MCGILLIS, W.R., GROSENBAUGH, M.A., Woods Hole Oceanographic Institution. Boundary layer flow in fish and squid.
A complete hydrodynamic understanding of aquatic locomotion requires knowledge of the thin boundary layer surrounding swimming organisms. In particular, tangential forces acting on the body surface are dependent on the distribution of velocity throughout the boundary layer. Fluid velocities tangent and normal to the bodies of swimming fish and squid were determined throughout the boundary layer (1–10mm thick) by digital particle image velocimetry (DPIV) and digital particle tracking velocimetry (DPTV). Scup (Stenotomus chrysops), smooth dogfish (Mustelus canis), mottled sculpin (Cottus bairdi) and long-finned squid (Loligo pealei) were observed. The friction drag on swimming fish was determined to be greater than the rigid body friction drag. No separation of flow was observed and the shape of boundary layer velocity profiles suggested that the fish were sensing and responding to the surrounding fluid to prevent separation. Both laminar and turbulent flow were observed in the boundary layer under various conditions, and flow sometimes oscillated between the two states with body phase. The behavior of the boundary layers of the carangiform swimming scup and the anguilliform swimming smooth dog-fish showed marked differences. Boundary layer flow in mottled sculpin, which spend most of their time stationary on the substrate, was shown to be greatly impacted by the orientation of the pectoral fins. The findings support the existence of different sensory functions in the lateral line system anterior and posterior to the pectoral fins as suggested by structural differences. In L. pealei, the boundary layer yielded estimates of friction drag, and the effect of boundary layer suction at the mantle intake was observed.
5.6 ANDERSON, F.E.*, FOSTER, P. G., Southern Illinois University, IL, The Natural History Museum, London. Tests of ecdysozoan monophyly using molecular sequence data.
Some analyses of 18S ribosomal RNA sequence data have supported monophyly of Ecdysozoa, a superphylum composed of taxa that possess periodically molted chitinous cuticles (e.g., Arthropoda, Onychophora, Priapula and Nematoda). The Ecdysozoa hypothesis already has been accepted by many researchers, and this hypothesis (particularly the proposed close relationship between nematodes and arthropods) has been used to understand enigmatic developmental and genetic patterns within Nematoda. Recently, however, evidence from multiple nuclear protein-coding genes has been presented suggesting that Ecdysozoa (or at least a Nematoda + Arthropoda clade) is not monophyletic. To evaluate support for ecdysozoan monophyly, we added nematode sequences to previously published alignments for the 18S gene and several nuclear protein-coding genes and reanalyzed the data using maximum parsimony and maximum likelihood (including heterogeneous ML models, in which model parameters such as base composition can be estimated separately for particular branches). We also analyzed alignments of two other genes (the nuclear elongation factor-1 alpha gene and the mitochondrial cytochrome c oxidase subunit I gene). Finally, we used a taxon jackknifing approach with the 18S, EF-1 alpha and COI alignments to assess the role of taxon sampling in estimating ecdysozoan relationships. Our findings suggest that support for Ecdysozoa across multiple data sets and taxon samples is not unambiguous, and we argue that the use of the Ecdysozoa hypothesis for inferring character evolution within Nematoda may be premature.
S11.4 ANDERSON, J.M.*, CHHABRA, N.K., Charles Stark Draper Laboratory. Maneuvering and stability performance of a robotic tuna.
The Draper Laboratory Vorticity Control Unmanned Undersea Vehicle (VCUUV) is the first mission-scale, autonomous under-water vehicle which uses vorticity control propulsion and maneuvering. Built as a research platform with which to study the energetics and maneuvering performance of fish-swimming propulsion, the VCUUV is a self-contained free swimming research vehicle which follows the morphology and kinematics of a yellowfin tuna. The forward half of the vehicle is comprised of a rigid hull which houses batteries, electronics, ballast and hydraulic power unit. The aft section is a freely flooded articulated robot tail with is terminated with a lunate caudal fin. Utilizing optimized body and tail kinematics from the MIT Robotuna experiments, the VCUUV has demonstrated stable steady swimming up to 2.4 knots and aggressive maneuvering trajectories with turning rates up to 75 degrees per second. This paper summarizes the vehicle maneuvering and stability performance observed in field trials and compares the results to predicted performance using theoretical and empirical techniques.
P3.48 ANDREWS, A.L.*, HATLE, J. D., CROWLEY, M.C., JULIANO, S. A., Illinois State University Hemolymph protein profiles during egg production in three populations of the Eastern lubber grasshopper.
Distant populations of a given organism can be predicted to have reproductive physiologies that are adapted to their local environment. For example, to avoid a reproductive output of zero, populations of univoltine species from locations with shorter growing seasons could be predicted to reproduce sooner than populations from locations with longer growing seasons. In particular, a transition from a developmentally flexible phase to a developmentally inflexible phase (that requires a set amount of time) could be expected to occur sooner in populations from shorter growing seasons. Lubber grasshoppers are univoltine and exhibit low vagility. In addition, they have flexible reproductive timing during the first half of the oviposition cycle but initiate inflexible reproductive timing during the second half of the oviposition cycle. The maximum titer of total hemolymph protein (=TPmax) in lubbers occurs during this inflexible phase. Here, we test whether latitudinally distinct populations of lubbers differ in their timing of reproductive development, as indicated by the timing of TPmax. We predicted that the time from adult eclosion to TPmax (i.e. the flexible phase) would be greatest in Florida, intermediate in Louisiana, and lowest in Georgia lubbers. Contrary to prediction, times from eclosion to TPmax did not differ among the populations. Time from TPmax to oviposition (i.e. the inflexible phase), however, was significantly greater for LA hoppers than GA hoppers. Our data suggest that the duration of the canalized phase differs among populations and raises the possibility that these differences may be adaptive for reproduction in the corresponding local environments. (Supported by NSF grant DB1-9978810 to SAJ.)
10.1 ANGILLETTA, M.J.*, LEE, V., SILVA, A.C., University of Pennsylvania, Philadelphia. How do embryos incubated at higher temperatures spend less energy during incubation?
In some reptiles, the energetic cost of development remains the same or even decreases with increased incubation temperature. The surprisingly low energy expenditure of embryos at high incubation temperatures may be caused by either of two mechanisms: 1) a shorter incubation periods coupled with a relatively low thermal sensitivity of metabolic rate, or 2) acclimation of metabolic rate to incubation temperature. In the eastern fence lizard, Sceloporus undulatus, incubation period is shortened by 50% when incubation temperature is increased by 10 C. Consequently, embryos must have a Q10 of 2.0 or lower to stabilize the energetic cost of development. Otherwise, thermal acclimation of metabolic rate must occur during development. We quantified the thermal sensitivity of embryonic metabolism in S. undulatus with repeated measures of metabolic rate at 27, 31, and 34 C. Similar to adult reptiles, metabolic rate of embryos increased significantly with increased body temperature, from 1.5 J h–1 at 34 C. The Q10 of metabolic rate from 27 to 31 C was only 1.6, which is much lower than Q10s of 2.0 to 3.0 that have been observed in adults. However, the Q10 of metabolic rate from 31 to 34 C was 2.7. Therefore, thermal acclimation must play a role in reducing the energetic cost of development at incubation temperatures that are higher than 31 C. We found that embryos did acclimate to incubation temperature; embryos incubated at 32 C had a lower metabolic rate than embryos incubated at 28 C, when both were measured at 30 C. Both the low thermal sensitivity and thermal acclimation of metabolic rate play a role in stabilizing the energetic cost of development in S. undulatus.
P2.59 ARDELEAN, A.*, FAUTIN, D. G., HUNSINGER, K., University of Kansas, Lawrence. Managing taxonomic synonyms.
Multiple names that refer to a single species (synonyms) and more than one species being referred to by the same name (homonyms) bedevil taxonomy. They produce ambiguity about the entity under discussion. We demonstrate an electronic application that helps organize information about synonyms and homonyms. Output from it can be used to generate synonym lists for taxonomic monographs. We illustrate its utility in testing taxonomic and biogeographic hypotheses. This research was supported by NSF grants DEB-9521819 and DEB-9978106 to DGF (in the program Partnerships to Enhance Expertise in Taxonomy), and OCE-0003970 to DGF and R. W. Buddemeier (in the National Ocean Partnership Program).
S7.11 ARP, A.J., RombergTiburon Center for Environmental Studies. The ecology and physiology of the marine echiuran worm, Urechis caupo: a model animal for demonstration of physiological principles.
Urechis caupo is a large echiuran worm endemic to the California coast. Populations of these worms inhabit individual, well ventilated, U-shaped burrows in the marine mudflat. Urechis is a non-selective filter feeder which uses an intricate mucus net to trap its particulate food. Although enriched in organic material, the mudflat habitat is subject to periodic exposure to toxic sulfide and hypoxia during low tide events. Over the last 14 years our laboratory group has investigated the ecophysiology of this animal — including the ecology, behavior, morphology, physiology, metabolism, and cellular biochemistry that allow it to flourish in the challenging mudflat environment. One overriding observation has emerged: this unique echiuran worm demonstrates numerous specialized adaptations that provide an excellent demonstration of a variety of physiological principles. This presentation will attempt to synthesize all we have learned from ecological and physiological studies, starting with Fisher and MacGinitie 1928, into an overview of the natural history and biology of this unusual animal, and will highlight the usefulness of Urechis as a model in the teaching and research laboratory.
P3.91 ASAY, M.J.*, BOYD, S.K., University of Notre Dame. Distribution of arginine vasotocin in the brain of a non-vocalizing anuran (Ascaphus truei).
Tailed frogs (Ascaphus truei) are endemic to the Pacific Northwest and are considered the most primitive extant anuran. In addition, unlike most anurans, they do not vocalize. Arginine vasotocin (AVT) is a neuropeptide that modulates many amphibian reproductive behaviors, including mating calls. The distribution of AVT-immunoreactive (AVT-ir) cells in the brain of Ascaphus could provide insight into AVT control of behavior in amphibians. We used immunocytochemistry and a rabbit polyclonal antibody raised against vasopressin to detect putative AVT-ir cells and fibers in brains from adult male and female Ascaphus. The overall distribution of immunoreactivity was more restricted in Ascaphus than previously reported for other anurans. Significant populations of AVT-ir cells were found in the magnocellular preoptic nucleus and suprachiasmatic nucleus in the diencephalon. A much smaller population of cells was found spanning the dorsal and ventral striatum. AVT-ir fibers were found in some areas that control vocal behavior in other anurans. AVT may thus have alternative functions in these areas in Ascaphus. Supported by NSF IBN95-14305.
S6.1 ASHLEY-ROSS, M.A.*, GILLIS, G.B., Wake Forest University, Harvard University. A brief history of functional morphology.
The discipline of functional morphology grew out of a descriptive comparative anatomical tradition; its transformation into a modern experimental science facilitated largely by technological advances. Early morphologists, such as Cuvier and Thompson, felt that function was predictable from organismal form, to the extent that animals and plants represented perfect adaptations to their habits. However, anatomy alone could not inform morphologists how organisms actually performed their activities. Recording techniques capable of capturing fast motion were first required to begin to understand animal movement. Muybridge is perhaps most famous for his pioneering work in fast photography, enabling him to "freeze" images of even the fastest horse at a full gallop. In fact, what functional morphologists now practice as kinematic analysis grew directly out of the techniques Muybridge developed. Marey, though lesser known than Muybridge, made perhaps an even greater contribution to experimental science through his invention of automatic apparati for recording events of animal motion. Thus functional morphologists could begin to make reasonable predictions of how the musculoskeletal system generated movement, as well as provide the structural foundations of form. In the middle of the 20th century, scientists discovered a way to record what the muscles of an awake, behaving animal were doing. The technique of electromyography, initially used extensively, in clinical applications, was co-opted as a tool of comparative functional anatomy by researchers such as Gans and colleagues. High-speed kinematic analysis and electromyography have for many years been the mainstay of experimental technique in functional morphology. In recent years, functional morphology has begun to branch out to incorporate approaches from other disciplines, and now stands at the threshold of becoming a truly integrative, central field in organismal biology.
P2.1 ASHRAF, M., NESBITT, R.A., LEE, C.M.*, Howard University, Washington, DC. Positioning of kinetoplasts in Trypanosoma musculi and Typanosoma lewisi during the development in-vitro.
Trypanosoma musculi is parasitic to mice and Trypanosoma lewisi is parasitic to rats, and both of these parasites are highly specific to their hosts. The development of Trypanosoma musculi and Trypanosoma lewisi were studied in vitro in the presence of adherent splenic cells. Both parasites developed only when attached by their flagellar tips to splenic adherent splenic cells. During the proliferation of T. musculi, the kinetoplast migrated towards the nucleus, and once in the vicinity of the nucleus, the nuclear division was triggered. Trypanosoma musculi divided as epimastigotes. The kinetoplast of T. lewisi did not migrate towards the nucleus but remained at its original location. The nucleus and kinetoplast divided at the same time. Both parasites started dividing from their flagellar ends and T. musculi and T. lewisi daughter cells were formed within 48 hour. Trypanosoma lewisi did not form rosette-like pattern around the adherent cells and remained as trypomastigote forms. It is also observed that after 48 hour in culture, T. lewisi were able to divide without attaching to the adherent cells. However, the unavailability of the adherent splenic cells in vitro led the parasites to transform into round nonviable forms.
4.2 AZIZI, E.*, LANDBERG, T., BRAINERD, E.L., University of Massachusetts, Amherst. Kinematics and performance of the escape response in an aquatic salamander, Eurycea bislineata.
Despite the large body of information on the aquatic escape response of fishes, the kinematics and neurobiology of fast-starts in salamanders remain poorly understood. We examine the effect of ontogenetic changes in morphology on escape performance in larval and adult two-lined salamanders, Eurycea bislineata. The two life stages of this lungless stream salamander overlap in body size. Body length in our sample ranged from 4.8 to 6.4 cm in larvae and 5.8 to 7.5 cm in adults. At metamorphosis, these salamanders lose the tail fin which reduces the lateral profile in the caudal region of the adults. Analysis of cross-sections at various body positions reveals a decrease in the relative muscle mass of adults. We elicited escape responses using tactile stimuli directed at the forelimbs of E. bislineata. The observed kinematics, which consist of a preparatory and a propulsive phase, resemble the C-starts described for numerous fish species. The duration of stage 1 (C-forming phase) was found to increase with body length. Maximum body curvature (measured at the end of stage 1) varied between larval and adult salamanders. Because differences in relative muscle mass and lateral profile have been shown to effect escape performance in fish, we hypothesize that the observed morphological and kinematic variation in larval and adult E. bislineata will lead to differences in escape performance.
P1.38 BACHMAN,G.C., University of Nebraska,Lincoln. Changes in leukocyte counts in hibernators from spring through summer.
At high elevations, hibernators such as Belding's ground squirrels (Spermophilus beldingi) emerge through snow and are unable to forage for the first few weeks of spring. Potentially, these individuals face a trade-off between allocating limited energy and nutrients to re-establishing physiological function, and the need to fuel activity associated with the brief breeding period which also occurs at this time. Immune function appears to be among the systems that show some degree of regeneration after emergence. Blood smears were collected periodically from squirrels from May (days after emergence) through August allowing me to follow changes in individual profiles over time. Two measures were taken from these slides - a differential leukocyte count and a measure of the relative number of leukocytes relative to erythrocytes. The analyses focus on the populations of immature and mature neutrophils, lymphocytes, and immature leukocytes as other cell types were rare. The time series indicate a progressive maturation of the leukocyte population and an increase in the relative number of leukocytes. Associations between leukocyte counts and individual behavior and body composition will also be presented.
P1.89 BAGATTO, B.*, WOLOSZYN, L., BURGGREN, W., University of North Texas. 3-D visual assessment of cardiovscular function in zebrafish larvae.
Numerous investigators are now measuring stroke volume of developing vertebrates by optical examination. The standard method for many animals, including zebrafish larvae, involves fixing the larvae, and capturing two dimensional video of lateral views of the beating heart through an inverted microscope. To arrive at a volume, the zebrafish heart is assumed to be in the shape a prolate spheroid. However, during early larval development, the zebrafish heart is shaped more like a tube, which begins to S-fold as it develops into its final shape. To assess stroke volume, and then, calculate cardiac output in these young larvae, a third dimensional measurement is needed. Our technique involves securing the living, intact larva, in a low temperature melting point agarose cylinder. The larva is then rotated through a full 180 degrees beginning at one lateral view, through the ventral view, to the other lateral view. The resulting three dimensional representation of the developing heart as it beats allows for more accurate calculation of diastolic and systolic volume, and hence stroke volume and cardiac output. In addition, this technique allows us to quantify the formation and three dimensional shape of vessels during early development. (supported by NSF IBN 98-96388).
P1.93 BAIER, D.B.*, GATESY, S., Brown University. The role of avian slow-twitch fibers in turkey tail display.
EMGs from the tail muscles of male turkeys (Meleagris gallopavo) vary in amplitude between flight and display. In flight, caudal tail muscles yield high amplitude EMGs typical of twitch fibers. In display, male turkeys fan, raise, and turn their tails with little or no EMG activity. Slow-tonic muscle fibers (type III) like those found in the avian M. latissimus dorsi cranialis were hypothesized to be responsible for display postures, which can be maintained for several hours. Such tonic fibers do not propagate action potentials thereby explaining lack of conspicuous EMG signals. Histochemical staining for mATPase was used to characterize tail muscle fiber types. The primary muscles involved in raising the tail (M. levator caudae pars vertebralis, M. levator caudae pars rectricalis) and in fanning (M. bulbi rectricium) all show mixed populations of slow-twitch (type I) and fast-twitch (type II) fibers. The muscle previously assumed to turn the tail (M. lateralis caudae) contains only fast-twitch (type II) fibers. No slow-tonic (type III) fibers have been identified in any caudal muscle. However, avian slow-twitch fibers are also multiply innervated, unlike mammalian slow-twitch fibers. Despite their innervation, avian slow-twitch fibers are often considered to be action potential-propogating. Our histochemical results, together with EMG activities, suggest that avian slow-twitch fibers are responsible for maintaing tail posture during display.
P3.33 BAKER, P.J., Miami University. Ontogenetic changes in plastral callosities of the Senegal flapshell turtle, Cyclanorbis senegalensis.
The number and location of the plastral callosities are reliable characters used to distinguish adults of the Senegal flap-shelled turtle, Cyclanorbis senegalensis, from its congener the Nubian flap-shelled turtle, C. elegans. Adult C. senegalensis have seven to nine callosities present on the plastron including five preplastral callosities whereas adult C. elegans have a maximum of four callosities with no preplastral callosities. However, difficulties in identification arise when comparing specimens of different sizes and sexes. After examining a large series of live C. senegalensis, with specimens ranging from juvenile to adult, I have observed that the development of the plastral callosities is determined by both the size and sex of the individual. Females attain a greater carapace length (CL) than males; and thus males develop a full complement of nine callosities at a smaller CL than females. The number, size, and shape of the plastral callosities of C. senegalensis can be used as both a character to distinguish male from female specimens, as well as a diagnostic character to distinguish between species.
P1.79 BAKKEN, G.S.*, WILLIAMS, J.B., Indiana State University, Terre Haute, Ohio State University, Columbus. Effect of wind and growth on the thermoregulatory metabolism of Arctic-breeding shorebird chicks
Many Arctic-breeding shorebird chicks leave the nest and forage with one or both parents soon after hatching. Chicks may be exposed to temperatures near 0°C, and tundra habitats offer little shelter from wind. Parental attentiveness prevents severe hypothermia, but foraging time may be limited by thermoregulatory competence. We used open-circuit respirometry to measure the oxygen consumption and evaporative water loss rates of downy chicks of 3 species of Arctic-breeding shorebirds, the least sandpiper, (Calidris minutilla), short-billed dowitcher (Limnodromus griseus), and whimbrel (Numenius phaeopus). Chicks ranged from 9 to 107g in mass and were generally 85 to 350 hours old during measurements. Measurements were made at wind speeds of 0.1, 0.8, 1.8 and 3.0 m/s. Air temperatures ranged from 15 to 30°C, depending on age and species, and were selected so that standard operative temperatures always fell somewhat below the lower critical temperature. While chicks can withstand temperatures below 10°C for short periods with no wind, they frequently became hypothermic during extended (2 hour) measurements below 20°C with wind. Normothermic body temperatures during measurements averaged 39 ± 1°C for dowitchers and whimbrels. Sandpiper body temperature increased with age from 37 °C at 170 hours to 39 °C at 220 hours. As wind u increased from 0.1 to 3 m/s, mass-specific thermal conductance, K (W/g-°C) increased 62% for sandpipers, 42% for dowitchers, and 35% for whimbrels. The combined effects of mass and wind are approximated by log (K) = –2.1 –0.54 log (m) + 0.055u.
S11.3 BANDYOPADHYAY, P.R., Naval Undersea Warfare Center, Newport, RI. Maneuvering hydrodynamics of fish and small underwater vehicles
The understanding of fish maneuvering and its application to underwater rigid bodies are considered. The goal is to gain insight into stealth. The recent progress made in NUWC is reviewed. Fish morphology suggests that control fins for good maneuverability have unique scalar relationships irrespective of their speed type. Maneuvering experiments are carried out with fish that are fast yet maneuverable. The gap in maneuverability between fish and small underwater vehicles is quantified. The hydrodynamics of a dorsal fin based brisk maneuvering device and a dual flapping foil device, as applied to rigid cylindrical bodies, are described. The role of pectoral wings in maneuvering and station keeping near surface waves is discussed. A pendulum model of dolphin swimming is presented to show that body length and tail flapping frequency are related. The mechanism of discrete and deterministic vortex shedding from the oscillating control surfaces has the property of large amplitude unsteady forcing and an exquisite phase dependence, which makes it inherently amenable to active control for precision maneuvering. Theoretical control studies demonstrate the feasibility of maneuverability of biologically-inspired bodies under surface waves. The application of fish hydrodynamics to the silencing of propulsors is considered. Two strategies for the reduction of radiated noise are developed. The effects of a reduction of RPM are modeled. The active cambering of blades made of digitally programmable artificial muscles, and their thrust enhancement, are demonstrated. Next, wake momentum filling is carried out by artificial muscles at the trailing edge of a stator blade of an upstream stator propulsor, and articulating them like a fish tail. A reduction of blade tonals is demonstrated theoretically.
P3.44 BARAGONA, M.A.*, HAIG-LADEWIG, L.A., WANG, S.Y., University of Southern Mississippi, Hattiesburg. Multiple paternity in the grass shrimp Palaemonetes pugio.
Microsatellite markers were used to study the mating system of Palaemonetes pugio. Grass shrimp genomic libraries were screened for clones containing di- or trinucleotide repeats. Positive clones were sequenced and PCR primers were designed for clones containing more than five tandem trinucleotide repeats or more than seven tandem dinucleotide repeats. Among the 11 microsatellite loci characterized, two were selected on the basis of polymorphism and ease of amplification to genotype 30 embryos from each of 10 brooding females collected from an estuary in the northern Gulf of Mexico. Results indicate that 8 of the 10 females were brooding embryos sired by more than one male.
58.5 BARKER, J.U., ASHLEY-ROSS, M.A.*, Wake Forest University. The effect of fiber type heterogeneity on work and power output of hindlimb muscles of the tiger salamander.
Most vertebrate muscles are composed of a mixture of fiber types. However, study of the mechanical performance of muscle has concentrated on homogeneous bundles of muscle fibers. Muscles in the hindlimb of the tiger salamander, Ambystoma tigrinum, present an excellent opportunity to explore the consequences of fiber heterogeneity on work and power output. Isometric twitches and work loops were performed in vitro on two muscles, the M. iliotibialis pars posterior (ILTP; heterogeneous, containing SO, FOG and FG fibers) and the M. iliofibularis (ILFB; homogeneous, containing FOG fibers only). Maximal isometric twitch force in the ILTP was over twice as great as in the ILFB; however, when adjusted for cross-sectional area, mean isometric stress was statistically indistinguishable (ILTP: 46.2 +/– 21.4 kN/m2; ILFB: 40.1 +/– 21.5 kN/m2). Work loops were performed over a range of frequencies (0.5 ñ 3.0 Hz) that encompassed the observed range of in vivo limb cycling frequencies.The homogeneous ILFB showed a steady decline in work per cycle from 1.5 ñ 3.0 Hz, while power output over those frequencies remained nearly constant. The heterogeneous ILTP showed a different pattern, with a tri-modal distribution for work per cycle with peaks at 0.5, 1.5, and 2.5 Hz, and maximal power output at 2.5 Hz. The differences in mechanical performance between the ILTP and ILFB may relate to the musclesí function during locomotion. The ILFB is active at the beginning of the swing phase, and serves to lift the hindlimb from the ground. Steady power output may be required for this ballistic-like movement, as the weight of the limb is unchanging. In contrast, the ILTP functions to extend the knee, and thus can contribute to forward propulsion. High power output at high cycling frequencies may indicate the ILTP assists fast locomotion.
P3.11 BARRIGA-SOSA, I.*, ARREDONDO-FIGUEROW, J. L., Universidad AutonÛma Metropolitana Unidad Iztapala. Morphological and allozyme variation in Chirostoma grandocule Steindachner (Pisces: Atherinopsidae) from Lake P·tzcuaro, Mèxico.
We investigated the levels of population differentiation of the silverside fish species Chirostoma grandocule Steindachner in Lake P·tzcuaro based on morphometric and allozyme data and relate such information to aspects of life history and changes in their natural habitat. We analysed eighteen morphometric characters, eight meristic and eleven putative enzyme-coding loci from C. grandocule samples of two different localities ("subpopulations") within the lake and of three different years (Janitzio 1996, 1999 and Ichupio 1997). Principal Component (PC) analysis with the morphometric data indicate the separation of two groups (grouped into four components, 66.78%). Among the variables that contributed the highest variation were: pelvic fin length of base (PfbL), head length (HL), eye diameter (ED), dorsal 2nd lengh (D2L) and snout length (SnL). Discriminant analysis (DA) with morphometric data also indicated separation between samples (87.10% correctly classified) Janitzio and Ichupio (Wilk's I= 0.13-48, P< 0.000). Allozyme data resolved seven polymorphic loci at P.99 level. C. grandocule showed levels of He that ranged from 0.0134 to 0.0319 (average HS = 0.0234). Genetic differences were observed between years and between "subpopulations", with six alleles of Janitzio never detected in Ichupio and one of Ichupio not present in both years of Janitzio samples. Genetic distances (DR & co-ancestry) between samples ranged from 0.0154 to 0.0341. Weir & Cockerham's F-statistics provided evidence of significant heterogeneity among "subpopulations" and years (jack-knifed qS = 0.0252, S.D. 0.0126). Our morphometric and allozyme results are consistent and suggest that Chirostoma grandocule is encountering an actual process of population differentiation in lake P·tzcuaro.
1.4 BARTOL, I.K.*, GORDON, M.S., University of California, Los Angeles. Flow patterns around boxfishes: role of body keels in dynamic stability.
The tropical marine boxfishes and their relatives (family Ostraciidae) are some of the most highly specialized living bony fishes. The forward 2/3 to 3/4 of their bodies are covered by rigid bony tests, which restrict body movements to their fins and the posterior sections of their tails. Recent field and laboratory observations indicate that these fishes demonstrate great maneuverability, dynamic stability, and course control. The diversity in body architecture and keel characteristics among the ostraciids makes it possible to determine the roles of the bony tests in maintaining stability. Various features of the tests of four morphologically distinct ostraciids were measured to develop a better understanding of body variation in this group. Flow patterns in the wakes and along the bodies of stereolithographic models of ostraciid fishes positioned at various angles of attack in a water tunnel were measured using digital particle image velocimetry (DPIV) to determine how test morphology impacts flow and ultimately dynamic stability. Significant differences in test characteristics, such as relative location of maximum test height/width, number and angle of keels, and degree of lateral/ventral body curvature, were detected among the four ostraciids. These differences impacted flow patterns around the models. At angles of attack greater than 5 degrees or less than –5 degrees, vorticies developed most prominently around sharp, ventral, posterior keels with adjacent concave channeling. These vortices, which occurred posterior to the center of mass and produced upward directed forces at positive angles of attack and down-ward directed forces at negative angles of attack, presumably provide self-correcting forces that aid rigid-bodied swimmers in pitch control. Supported by ONR grant N00014-96-0607.
S9.2 BARTON, B.A., University of South Dakota. Stress in fishes: a diversity of responses.
Fishes display a wide diversity in their physiological responses to stress. Primary endocrine responses to acute stress include the release of catecholamine and corticosteroid hormones into circulation. Corticosteroids, chiefly cortisol, are released by the interrenal tissue, the adrenal homologue in fish, which is concentrated in the anterior portion of the kidney in teleostean fishes but found more diffusely scattered throughout the kidney in chondrosteans. Elevations in circulating cortisol during the first hour after an acute disturbance can increase from relatively low resting levels to between about 20 and >1,000 ng/mL, depending on species. Basal teleost groups, such as salmonids, generally exhibit lower responses than derived species, such as the percids, although environmental and developmental factors strongly influence the stress response in fish. Some of these factors include temperature, nutritional state, water quality, and prior exposure to stressors. Chondrosteans, specifically scaphirhynchid sturgeons and paddlefish, show post-stress cortisol elevations to <10 ng/mL following a similar acute stressor, which is much lower than those in teleosts. These differences in primary responses appear to be reflected in their secondary physiological responses to stress, such as changes in plasma glucose, lactate and chloride, which also appear to be much lower in chondrosteans than in teleosts. Brain serotonergic activity, which has been implicated in regulation of the hypothalamic-pituitary-interrenal axis during stress, also appears to be appreciably lower in chondrostean fishes than in teleosts. To date, little comparative work has been done in elasmobranch fishes, which release 1ALPHA-hydroxycorticosterone as the principle corticosteroid.
P1.37 BAUMANN, N.L.*, LIGHT, D.B., Ripon College. Purinergic receptor activation leads to a calcium-sensitive volume decrease in mudpuppy erythrocytes.
Regulatory volume decrease (RVD) in mudpuppy (Necturus maculosus) erythrocytes has been shown to depend on ATP–, Ca2+–, and phospholipase A2 (PLA2)-dependent pathways (Light et al. 1997. J. Membr. Biol. 158: 229). This study was designed to determine the relationship between these agents during RVD. The hemolytic index (HI) decreased with extracellular ATP (50 MICROmolar) and the Ca2+ ionophore A23187 [GenBank] (0.5 MICROmolar). In contrast, HI increased with the purinoceptor antagonist suramin (100 MICROmolar) and the PLA2 inhibitor ONO-OS-082 (10 MICROmolar). Interestingly, A23187 [GenBank] (0.5 MICROmolar) reversed the inhibitory effect of suramin (100 MICROmolar), indicating the Ca2+-dependent step was downstream of a P2 receptor. Extracellular ATP (50 MICROmolar) did not reverse the antagonistic affect of ONO-OS-082 (10 MICROmolar), suggesting that P2 receptor activation occurred prior to production of arachidonic acid. The percent volume recovery of cells following hypotonic shock (0.5X Ringer), measured with a Coulter counter, increased with extracellular ATP (50 MICROmolar) and A23187 [GenBank] (0.5 MICROmolar). In contrast, suramin (100 MICROmolar) inhibited volume recovery; this inhibition was reversed with A23187 [GenBank] (0.5 MICROmolar). Finally, using the whole-cell patch clamp technique, we found ATP (50 MICROmolar) enhanced a K+-conductance that was activated during cell swelling. This current was inhibited by ONO-RS-082 (10 MICROmolar) and suramin (100 MICROmolar). Conclusion: our results are most consistent with extracellular ATP activation of a P2 receptor occurring prior to a rise in intracellular Ca2+. This, in turn, activates PLA2 and subsequent K+ efflux through a conductive pathway. (Supported by NSF grants MCB-9603568 and MCB-0076006.)
P2.58 BEACHUM, C.*, STRANGE, R., Southeast Missouri State University. An evaluation of phylogeny inference programs and packages.
Phylogenetic inferences from large data sets can be problematic, with conflict between precision and minimal computer time determining the design of computer packages. We analyzed two large DNA data sets obtained from GenBank and a smaller homoplasy-rich morphological data set to demonstrate inconsistencies among three phylogeny building packages (PHYLIP, HENNING86, and PAUP*4.0). The sequence data was analyzed under the criterion of maximum parsimony, maximum likelihood, neighbor joining, and bootstrap where applicable. HENNING86 performed well as a parsimony engine, consistently finding the shortest tree in the least amount of time. However it is the oldest of the four packages and is the only one not offered for Unix, Windows, and Mac operating systems. Random Cladistics is a free upgrade that allows many different analyzing methods. PHYLIP3.5 is a free package that can perform many different analyzing methods. It is slow and retains an upward limit of only 100 trees, regardless of the number of equally parsimonious trees. Despite its problems, PHYLIP is free, has the best online help, and is a well integrated package. An alpha version of PHYLIP3.6, released this year, is still slow. It is more plastic and has added an adjustable maximum number of trees. PAUP*4.0 is the most refined of the four programs. It has the greatest number of available options. It is relatively quick and easy to navigate in the point and click format. However, the available options may be daunting to novice users. PAUP* is the best overall package for serious researchers. Researchers and educators need to consider their requirements before committing themselves to specific programs.
P1.27 BEAULIEU, L., ALLEN, S., BURNETT, K., BURNETT, L.*, College of Charleston, University of Charleston, SC, University of Charleston, SC, University of Charleston, SC. Low ph effects on the killing activity of oyster hemocytes.
An assay was used to measure the ability of hemocytes of the Eastern oyster, Crassostrea virginica to kill the bacterium Vibrio parahaemolyticus. Experiments were carried out at pH 7.6 and 6.6 mimicking the in vivo hemolymph environment within the oyster under well aerated conditions (7.6) and during air exposure (6.6). Assays were carried out using 96-well plates to expose hemocytes to Vibrio (1:20 ratio) for 3 hours at room temperature during which time the hemocytes phagocytized the Vibrio. The phagocytosis stage of the assay was terminated by adding 0.2% Tween to the wells, killing the hemocytes but not the Vibrio. A culture medium was then added to each well and the remaining Vibrio allowed to grow for 2 hours. The number of live Vibrio in each well after the growout period was measured using a colorimetric cellproliferation assay. A killing index was calculated based on the number of Vibrio in wells with hemocytes compared to their control wells (i.e., with hemocytes killed at time zero). A killing index of Vibrio was expressed as a percentage of the control, e.g., where an index of 50% indicates that 50% of the bacteria were killed by hemocytes. The average killing index at pH 7.7 was 49.2 (1.86 SEM; n=4) and lower, but not significantly different at pH 6.6, 38.8 (1.80 SEM; n=4). Under these assay conditions hemocyte viability, as judged by trypan blue exclusion, was high at the beginning of the assay (90.4–98% viable at pH 7.6; 87.4-95% at pH 6.6) and remained high for three hours (83.2–92% viable at pH 7.6; 86–92% at pH 6.6). These results suggest that low pH does not cause a significant reduction in the killing activity of oyster hemocytes. Supported by NSF-REU DBI-9876926 & ODRP NA96RG0488.
P2.82 BECK, A.L.*, BLOB, R.W., HOPSON, J.A., University of Chicago, IL, Field Museum, Chicago, IL, University of Chicago, IL. Morphological indicators of sprawling and nonsprawling limb posture in tetrapods.
Determination of locomotor postures in fossil tetrapods is difficult because their behavior cannot be observed directly. To evaluate morphological indicators of limb posture that could be used to interpret stance in extinct tetrapods, we have used multivariate statistical analyses to explore osteological correlates of locomotor posture in extant species. Our sample of extant taxa includes generalized mammals, lizards, and crocodilians spanning a large size range. Morphological measurements and observations relevant to locomotor function were taken from the forelimb, hindlimb and girdle skeletons of museum specimens. Principal components analyses as well as bivariate comparisons of limb and girdle elements indicate strong differences between sprawling and non-sprawling taxa. For instance, highly sprawling taxa are characterized by limbs with high angles of femoral torsion, short metatarsals, and reduced articular surfaces on the distal humerus. In contrast, nonsprawling taxa show significantly smaller surface areas than sprawling taxa for the hip, knee, and ankle joints. These analyses suggest several quantifiable morphological features that could aid the evaluation of limb postures in fossil taxa, thereby facilitating the evaluation of changes in limb posture over the evolution of mammalian locomotion.
P2.15 BECK, S. L., DePaul University. Skeletal variation by "batch" among CD-1 mice reveals continuing genetic heterogeneity.
The random-bred CD-1 mouse is widely favored as a test organism by regulatory agencies, pharmaceutical houses, among others, because of their broad array of genotypes, mimicing the human population. There is, therefore, concern about their continuous genetic heterogeneity. We purchased 7 groups of CD-1 mice from the same supplier, over a period of several years. The present study compares untreated controls from these 7 "batches", at 60–65 days post natal, for 88 normally-occurring skeletal variants. Most of the skeletal variants examined each strain-specific values among inbred strains and so are a good indicator of variation. There was significant (P<0.01) variation between groups among 63 variants. Seventeen variants never appeared, and 9 occurred in only 1 specimen in all 7 groups (686 mice). High variability among all groups was seen for 10 variants. Average number of variants for each group that differ in 2-way comparisons with each of the others, and ranges, are: G1 = 21 / 16–26, G2 = 18.2 / 16–23, G3 = 20 / 16–23, G4 = 16.7 / 10–26, G5 = 13.8 / 9–19, G6 = 16.5 / 9–25, G7 = 16.2 / 13–22. The variants showing the largest number of significant comparisons were doubled Mandibular Foramen (18 of 21 possible comparisons), doubled Foramen Pterygoideus (15), imperfect Transverse Foramen on cervical vertebra (CV) 7 (15), Arch Foramen CV5 (15), Parted Frontal bones (14), Malformed Sternebrae (14), anteriad suture on posterior border of the Palatine bone (14), perforated Fossa Olecrani of the humerus (13), and caudalized Sacral Vertebra 3 (12). The sizeable number of variants which differ significantly in these 7 groups of CD-1 mice purchased over a period of several years suggest that these animals continue to be morphologically diverse. (Supported by the Department of Biological Sciences and the University Research Council of DePaul University).
16.2 BECKMAN, B. R.*, FAIRGRIEVE, W., COOPER, K.A., MAHNKEN, C. V.W., DICKHOFF, W.W., Northwest Fisheries Science Center, National Marina. Endocrine correlates of growth in ocean dwelling coho salmon.
Pacific Salmon typically spend 1–3 years foraging and growing in the ocean prior to returning to freshwater spawning sites. Inter-annual differences in ocean temperatures and productivity may have profound effects on the growth of these animals. Growth variation may influence age of maturation, size at maturation, and overall year-class survival. Thus, understanding variation in oceanic growth rates is important to understanding variation in the fitness of Pacific salmon. However, it is very difficult to measure oceanic growth rates. Growth is mediated by the endocrine system; consequently, endocrine correlates of growth may provide a valuable tool for assessing relative growth rate and related fitness values, based on a single blood sample. We conducted an experiment relating growth rate to plasma hormone levels in order to test this idea. Specifically, we individually tagged approximately 1200 yearling coho salmon, placed them in seawater tanks and assessed growth at two month intervals. Plasma was obtained in September and November and we found a significant, highly correlated (r2>0.5) relation between IGF-I and growth rate. We found little relation between insulin and growth. Subsequently, we obtained samples from coho salmon in the Strait of Georgia and Puget Sound (West Coast of North America). IGF-I data obtained from these samples shows both geographic and interannual variability. These preliminary data suggest that a more extensive sampling regime (geographically and temporally) for IGF-I levels of Pacific salmon may give us insight into environmental factors regulating growth and fitness.
38.5 BEE, M.A.*, GERHARDT, H.C., University of Missouri, Columbia. Getting to know you: habituation as a mechanism for territorial neighbor recognition.
Territorial animals commonly exhibit low levels of aggression toward familiar neighbors in their usual territories and high levels of aggression toward strangers and neighbors in novel locations. Vocal recognition of neighbors is well known in songbirds, and also has been demonstrated in bullfrogs, Rana catesbeiana. Habituation has been suggested as a learning mechanism for neighbor recognition. However, no study has tested the hypothesis that repeated exposures to a neighbor's acoustic signals allow territorial animals to learn about individually distinct signal properties and the usual location of signal origin. We conducted 3 field playback experiments using a habituation/ discrimination procedure to test the hypothesis that habituation functions as a mechanism of neighbor recognition in bullfrogs. Synthetic bullfrog calls were broadcast to territorial males during a habituation phase until aggressive responses declined. We then presented novel stimuli during a subsequent discrimination phase. In experiment 1, a change in fundamental frequency, an individually distinct call property, elicited renewed aggression. In experiment 2, a 180° change in stimulus location elicited renewed aggression. In experiment 3, changes in fundamental frequency, location, or both frequency and location elicited renewed aggression. Responses were highest to changes in fundamental frequency, and these responses were independent of location; responses to changes in location alone were intermediate between responses to changes in frequency and controls. Our data indicate that repeated exposure to a neighbor's call resulted in stimulus-specific and location-specific response decrements, suggesting that habituation could function as a mechanism for neighbor recognition in bullfrogs.
5.3 BEGOVIC, E., University of California, Berkeley. Feeding specialization and diversification patterns of eastern Pacific Patellogastropoda.
To investigate the role that feeding specialization may play in clade diversification and mode of speciation, I have begun preliminary phylogenetic and sterol analyses of Eastern Pacific Patellogastropoda. A phylogenetic hypothesis for Eastern Pacific Patellogastropoda is constructed using mtDNA sequences from the large ribosomal subunit (16s). This phylogeny identifies two putative new species that have sympatric distributions with their respective sister taxa. Both of these taxa share common resources and similar ecotypic forms with their closest sister taxa, indicating that resource partitioning may not have played a significant role in their diversification. This phylogeny also confirms that L.austrodigitalis (Murphy, 1978) is the sibling species of L.digitalis, two species with parapatric distributions overlapping in central California and similar ecotypic forms. This pattern is consistent with the hypothesis that these species diversified as a result of vicariance. Finally, 16s data indicate that L.instabilis and L.ochracea are two distinct ecological forms of the same species. A re-evaluation of the systematics of patellogastropod species is needed. Preliminary analyses have been used to identify biogenic sterols in a subset of lottid taxa. Sterols incorporated into shell and body tissues can be used to identify diet in recent and fossil gastropods. These sterols can be used to determine past ecologies of fossil patellogastropods, whether resource partitioning exists at finer levels, if resource partitioning has changed through time within lineages, and to identify specialist versus generalist forms. Mapping these data onto a phylogenetic tree will allow me to examine the evolutionary history of feeding and resource partitioning of patellogastropods, which may shed light on the role of feeding specialization in clade diversification.
P1.12BELDEN, L.K.*, MOORE, I.T., BLAUSTEIN, A.R., Oregon State University, Corvallis, University of Washington, Seattle, Oregon State University, Corvallis. Survival and the physiological stress response in Cascades frog tadpoles exposed to ambient UV-B radiation in the field.
Global environmental changes, includingincreases in ultraviolet-B radiation (UVB;-280–320 nm), are receiving attention from biologists interested in how these changes will alter community and ecosystem structure and function. However, we know little about how factors such as UV-B affect animals physiologically. Amphibians provide a good model system for examining the physiological effects of UV-B exposure because basic studies documenting both lethal and sublethal effects have been completed on a wide array of species at many life history stages. In this study, we examined the physiological stress response, as measured by glucocorticoid hormones, and survival of Cascades frog tadpoles, Rana cascadae, exposed to ambient UV-B in the field for 6 weeks. There were no differences in corticosterone levels between exposed and non-exposed tadpoles, although survival was significantly higher in the tadpoles shielded from UV-B. Even though UV-B exposure can be lethal for Rana cascadae tadpoles, in this study we did not observe a physiological stress response. However, the stress response in this species is poorly understood and there are several factors, including the length of the study, the ability of tadpoles to perceive UV-B, and the timing of development of the stress axis, that could explain the lack of a physiological stress response.
P2.32BENNETT, V.A., STEED, J. N.*, LEE, R.E., KUKAL, O., Miami University, Oxford, OH. Atlantic Low Temperature Systems, Ltd., Halifax, Nova Scotia. A description of Gynaephora groenlandica hibernacula sites and behavioral preferences for light, temperature, and soil moisture related to microhabitat selection.
G. groenlandica caterpillars overwinter in hibernacula anchored at the base of rocks on the Arctic tundra. At each of two study sites on Ellesmere Island, hibernacula were consistently found on the same aspect of the rocks, possibly related to prevailing winds and/or patterns of snow accumulation. Hibernacula temperatures were slightly warmer and more buffered than ambient temperatures. How do caterpillars select suitable microhabitats for hibernacula? Laboratory experiments tested for behavioral preferences based on light, temperature, and soil moisture conditions. Both active caterpillars and those entering hibernation showed strong preference for light over dark conditions. Along a 0–25°C temperature gradient, most caterpillars settled at the warmest region (21–25°C), indicating that they may select hibernacula sites based on thermal cues. However they do not appear to select colder microhabitats, as we had hypothesized, as a means of metabolic depression for energy conservation in late sumer and fall. Active caterpillars showed no preference based on soil moisture, however most caterpillars entering hibernation preferred low soil moisture (0–10%), which may be indicative of microhabitats where snow melts earliest in Spring.
11.5BENNETT, V.A.*, KUKAL, O., LEE, R.E., Miami Univeristy, Oxford, OH, Atlantic Low Temperature Systems, Ltd., Halifax, Nova Scotia, Miami University, Oxford, OH. Seasonal metabolic depression and mitochondrial degradation in Arctic woollybear caterpillars, Gynaephora groenlandica.
Gynaephora groenlandica requires 7–14 years to complete its life cycle, overwintering as many times. Because of the short active season (3–4 weeks in June), these caterpillars may spend as much as 90% of their lives in dormancy without feeding. Therefore energy conservation is especially important for their survival in this extreme environment. At the end of June, when the majority of arctic insects are just beginning their summer active period, G. groenlandica caterpillars enter hibernation, probably as a means of temporally avoiding parasitoids. Therefore, even in hibernation, G. groenlandica experience the warmest summer temperatures in July and early August that could potentially elevate metabolic rate causing depletion of energy reserves. To conserve energy, G. groenlandica exhibit a seasonal metabolic depression associated with hibernation: respiration rates of late-season caterpillars were as much as 50% lower than those of active caterpillars, and they were relatively insensitive to temperature (Q10
1.5). A previous study demonstrated that cold-acclimated G. groenlandica had fewer mitochondria in brain and fat body tissues than warm-acclimated caterpillars. Could this mitochondrial degradation be the mechanism of metabolic depression? Using confocal microscopy and digital image analysis, mitochondria were quantified in tissues of both active and hibernating stages of G. groenlandica. Initial data show a 54% reduction in the number of mitochondria in fat body tissue of hibernating versus active caterpillars, and as much as a 65% reduction in the number of mitochondria in muscle tissue.
54.5 BERNAL, D.*, DICKSON, K., GRAHAM, J., Scripps Inst. Oceanography, Cal. State University, Fullerton. Convergence for high performance swimming in lamnidsharks and tunas. Thermoregulation and metabolic biochemistry.
This study documents the shortfin mako shark's (Isurus oxyrinchus) capacity to thermoregulate and the thermal effects on metabolic enzymes activities and compares the results to tunas. Elasmobranchs and bony fishes have evolved independently for more than 400 million years. However, two Recent groups, the lamnid sharks and tunas, display remarkable similarities in features related to swimming performance. Traits separating these two groups from other fishes include a higher degree of body streamlining, a shift in position of the aerobic locomotor muscle (red muscle, RM) that powers sustained swimming to an anterior position in the body and to near to the vertebral column, an increased gill surface area, a higher blood oxygen carrying capacity, the capacity to conserve metabolic heat (i.e., endothermy), and greater muscle aerobic and anaerobic enzyme activities at in vivo temperatures. The suite of morphological, physiological, and biochemical specializations that define "high-performance fishes" have been extensively characterized in the tunas. This study uses the convergent features of lamnids and tunas in order to gain insight into the extent that comparable environmental selection pressures have led to the independent origin of similar suites of functional characteristics in distinctly different taxa. This study tests the hypothesis that, despite differences between teleost and elasmobranch fishes, lamnids and tunas, have evolved morphological and physiological specializations that enhance their swimming performance relative to other sharks and most other high performance pelagic fishes.
P2.95BERTRAM, J.E.A.*, RUINA, A., COX, D.E., KATSANOS, C. S., Florida State University, Tallahassee, Cornell University, Ithaca, Florida State University, Tallahassee, Florida State University, Tallahassee. Speed, step length and frequency in human walking: evaluating the optimization criteria.
Locomotion is an active process that involves an interaction between physiological and physical features of an organism. The result of this interaction is the overt functional behavior of the system, its capabilities and limitations. But can the physiological and physical influences be discriminated? We use the walking human as a model system to investigate the factors influencing gait pattern, as indicated by the selection of step length and frequency to provide walking speed. We hypothesize that the selection of these variables depends on the minimization of the locomotory cost function under the explicit circumstances involved, i.e. the solution is a constrained optimization. We compare walking behavior of 6 male and 6 female subjects with predictions based on individual locomotion cost. The results verify the basic model, but also demonstrate that other factors influence the outcome as well.
50.3BETTENCOURT, B.R.*, FEDER, M.E., University of Chicago. Concerted evolution and concerted degeneration at the hsp70 genes and pseudogenes of the Drosophila melanogaster species subgroup.
To determine how the hsp70 genes (4–5 copies total, at two chromosomal loci) coevolved with the diversification of the D. melanogaster species subgroup, we sequenced multiple alleles of each gene in representative species. The hsp70 genes display strikingly different patterns of molecular evolution among the eight species of the subgroup. In D. simulans and D. melanogaster, frequent gene conversion homogenizes all the hsp70 coding sequences, diversifies flanking sequences, and interacts with both purifying and balancing selection to drive rapid concerted evolution. By contrast, hsp70 pseudogenes are common in D. mauritiana: null alleles of three of the four hsp70 genes are at high frequency. These pseudogenes also participate in gene conversion; copies at different loci share the same degenerative mutations. The hsp70 genes of D. orena, basal member of the subgroup, evolve in a fashion similar to those of D. simulans. While hsp70 expression level, thermotolerance, and thermal niche breadth are strongly coupled to the hsp70 genes in D. melanogaster, the functional copy number and relative "health" of the hsp70 genome is only a fair predictor of these traits in other species. If, when, and how natural selection acts on the hsp70 genes varies in a lineage- and locus-specific fashion.
P2.84 BETZ, O.*, MUMM, R., Universitaet Kiel, Tieroekologie, Universitaet Kiel, Phytopathologie. The predatory legs of Philonthus marginatus (Coleoptera,Staphylinidae): functional morphology and tarsal ultrastructure.
Within the Coleoptera, no predatory legs have become known thus far. However, within the staphylinid genus Philonthus representatives of the subgenus Onychophilonthus are distinct from other subgenera by the structure of their prolegs: both sexes have elongated coxae and enlarged tarsomeres I-IV. The claws can be bent downward to a large extent, thus almost setting against the ventral side of tarsomere V. We present the results of (a) behavioural observations concerning predatory performance, (b) motion analysis of the predatory strike, and (c) morphological examinations of the prolegs by light, scanning and transmission electron microscopy.These examinations were aimed to develop a functional model of this advanced prey capture mechanism.The predatory behavior of these beetles can be subdivided in three parts: (a) attempting an ambush, (b) predatory strike, and (c) formation of a catching basket. The mean total duration of the strike from the onset of the proleg till the first prey contact amounts to 31.6 ms. The movements of the prolegs during the strike can be subdivided in three components: (1) upward swing, (2) downward strike, (3) withdrawal. The structure of the coxotrochanteral articulation and the high speed of the downward strike (7 ms) suggest a prestress mechanism, consisting of the cocontraction of the trochanterofemoral flexor and levator muscles. In addition, a coxal projection that fits into a trochanteral groove when the leg is flexed, serves as a cuticular supporting structure. The ultrastructure of the protarsi I-III demonstrates the rich development of epidermal glands, which probably produce an adhesive secretion. By this means, under mediation of tarsal adhesive setae, the prey can be fixed at the moment of contact, thus enabling the beetles to capture even fast-fleeing prey such as springtails.
23.6 BIRCH, J.M.*, DICKINSON, M.H., University of California, Berkeley. Dynamic stall of a flapping appendage in the absence of a spiral vortex.
Recent studies of insect flight describe how dynamic stall and the formation of a leading edge vortex generate large lift forces for insects. This leading edge vortex, along with forces generated through rotation and wake capture, accounts for all lift necessary for insects to fly. This vortex is present throughout the translation portion of the wingbeat cycle and has been shown to grow in size from the base toward the wing tip. It has been hypothesized that fluid spirals outward through the center of this vortex, draining energy from the core, allowing the vortex to remain stable throughout the stroke. Using a robotic flapping model of a Drosophila wing, we visualized the flow of fluid around the wing and reconstructed the flow structure using digital particle image velicometry. At mid-downstroke, the leading edge vortex consists of a large sheet of vorticity that stretches back from the leading to trailing edges of the wing. However, unlike the flow pattern seen in the hawkmoth, Manduca sexta, flow within the leading edge vortex was < 5% of wing tip velocity. We tested the idea that this axial flow was necessary to maintain the stability of the leading-edge vortex. Using both a wall that circumscribed the wing sweep as well as fences on the wing, we inhibited axial flow through the vortex core. When axial flow was not permitted off the wingtip (the wall case), the tip vortex detached from the wing more distally and forces generated by the wing increased by at least 14%. Fences had little effect on force generation. From these experiments we hypothesize that in Drosophila, axial flow has little effect on the stability of the leading edge vortex, and thus its size is not the limiting factor when determining the performance of a flapping appendage.
P1.61BIRCHARD, G.F.*, DAUGHERTY, C.H., George Mason University, Fairfax, Victoria University of Wellington, New Zealand. Energetic of development in the fairy prion (Pachyptila turtur).
Embryos of the Procellariiformes are noted for their very long incubation times. The limited data available on embryos from this group indicates that these long development times are associated with increased costs of development. We measured the oxygen consumption rate of developing embryos of the fairy prion (Pachyptila turtur), a small procellariiform, from early in incubation until internal pipping (IP) occurred. Average egg mass in this species was 25g. The oxygen consumption rate showed an exponential rise with time. There appeared to be a short plateau period two days prior to IP which occurred on day 42 of an estimated incubation time of 44.5 days. The pre-IP oxygen consumption rate averaged 238 ml O2/d. Integration of the area under the curve to the time of IP gave a total of 2924 ml O2 consumed, a pre-IP cost of development of about 57.4 kJ. The incubation time of the fairy prion is 188% of the value predicted from existing allometric equations. The pre-IP energy consumption was not significantly different from predicted values. The cost of development was increased (184% of predicted values) as previously observed in this group. Analysis of deviations from predicted values for incubation time and cost of development for procellariiform embryos shows a significant effect of egg mass. Decreasing egg mass shows a consistent increase in the deviations observed.
P2.93BISHOP, K., Brown University. Evolutionary patterns in bat wing shape.
Among mammals, bats are the only group to have evolved powered flight. The changes which allowed the adoption of this locomotor mode include the modification of the forelimb into a wing. Features of the wing shape such as wing loading, aspect ratio, and tip index affect the aerodynamic performance of the wing. These measurements have been made by Norberg and Rayner, who analyzed them in an ecological context, but they have yet to be examined in an evolutionary context. I have mapped these measurements onto a well-supported phylogeny of the order Chiroptera in order to evaluate evolutionary patterns in wing shape.
36.6 BIXLER, A., TANG-MARTINEZ, Z.*, University of Missouri-St. Louis. Mate choice in prairie voles: effects of genetic relatedness and familiarity.
Prairie voles, Microtus ochrogaster, are monogamous rodents. We examined the mating choices of sexually inexperienced male and female prairie voles in two-way choice tests under 3 different conditions. Subjects were tested with targets that were 1) either a familiar sibling or an unrelated and unfamiliar vole; 2) a sibling and an unrelated vole, both of which were unfamiliar; or 3) two siblings, where one was familiar and the other unfamiliar. Intrommission was the criterion for mating. In condition 1, all voles that mated did so with the unfamiliar and unrelated conspecific. In condition 2, there was no significant preferences between the two targets. In condition 3, only one of 17 subjects mated, suggesting that voles avoid mating with siblings even when they are unfamiliar to the subject. The results of other measures related to reproductive behavior (e.g., time visiting, anogenital investigation, time in contact, agonistic interactions)-will also be reported. In most cases these measures were consistent with the mating preferences. However, we also found that interaction of pairs that mated were significantly more agonistic as compared to those of pairs that did not mate. Additionally, social preference (time spent visiting a target) did not always correspond to mating preference. We conclude that both relatedness and familiarity are important in the mate choices of prairie voles and that time spent visiting is not an adequate measure of mating preferences.
P2.10BLACKBURN, D.G.*, JOHNSON, A.R., PETZOLD, J.L., Trinity College, Hartford. Histology of the extraembryonic membranes of the oviparous corn snake, Elaphe guttata.
The extraembryonic membranes of amniote eggs serve vital nutritional and respiratory functions throughout development. However, very little is known about the structure and function of these membranes in oviparous reptiles. We examined extraembryonic membranes of the corn snake Elaphe guttata (Colubridae), using resin -embedded tissues sectioned on glass knives. Following oviposition, the embryos develop a chorioallantois as well an omphalallantoic membrane. The chorioallantois is highly vascularized, and its capillaries are separated from the inner lining of the eggshell by a bilayered epithelium that progressively thins during development. Small basophilic granules, possibly taken up from the eggshell, accumulate in apices of the epithelial cells. Depletion of yolk leads to expansion of the chorioallantois at the expense of the yolk sac. The omphalallantoic membrane forms through penetration of the allantois into the yolk cleft. The isolated yolk mass (IYM) undergoes progressive reduction, transforming into isolated patches of yolk droplets that are underlain and surrounded by the allantois. Yolk of the IYM appears to be digested by the bilaminar omphalopleure as well as by the allantois and motile cells with phagocytic capabilities. Diminution of the IYM and the overlying epithelium lead to close approximation of the allantoic capillaries to the eggshell throughout the abembryonic hemisphere of the egg. Consequently, for the last weeks of development, the egg is surrounded by thin vascularized membranes that presumably function in respiratory exchange. To better understand their functional morphology, we currently are examining cell ultrastructure of these membranes with electron microscopy.
64.5 BLACKSTONE, N.W., Northern Illinois University Redox state, reactive oxygen species (ROS), and adaptive growth of hydroid colonies.
Redox chemistry, involving the transfer of electrons and hydrogen atoms, is central to energy conversion in respiration, and control of gene expression by redox state commonly occurs in bacteria, allowing rapid response to environmental changes. Colonial hydroids often encrust surfaces over which the food supply varies in time and space; hence, in these organisms redox control of the development of feeding structures (polyps) and gastrovascular connections (stolons) could be similarly adaptive, allowing colonies to adjust the timing and spacing of these structures in response to a variable food supply. Feeding triggers strong contractions of polyp epitheliomuscular cells, resulting in high rates of gastrovascular flow. In fed polyps, this metabolic demand shifts the redox state of these cells in the direction of oxidation and diminishes the rate of formation of mitochondrial ROS. On the other hand, after 24 h without food, polyp epitheliomuscular cells become quiescent, redox state shifts in the direction of reduction, and formation of mitochondrial ROS increases. Perturbations of redox state and ROS can also be initiated using uncouplers of oxidative phosphorylation and inhibitors of the mitochondrial electron transport chain. The effects on colony pattern formation are similar; relative oxidation results in high rates of polyp and stolon tip initiation, while relative reduction results in low rates. As in other systems, ROS may mediate the effects of redox state; high levels of ROS may suppress the gene activity that leads to polyp and stolon tip initiation, while low levels of ROS may be permissive in this regard. In this way, metabolic demand, redox state, and ROS may interact to control pattern formationin hydroid colonies and to allow adaptive-growth forms in response to the food supply and other environmental factors.
55.3 BLANK, J. M.*, DAVIE, P. S., MORRISSETTE, J.M., BLOCK, B.A., Stanford University, Pacific Grove, CA, Massey Palmerston North, New Zealand, Stanford University, Pacific Grove, CA, Stanford University, Pacific Grove, CA. Effects of temperature on cardiac performance in yellowfin tuna.
Tunas are remarkable among teleosts for their endothermy, high metabolic rates and high capacity for exercise. While tunas warm their swimming muscles and viscera, their hearts are thought to remain near ambient temperature. This raises the possibility that cold water may impair cardiac performance in vivo, limiting the scope for metabolism of tuna in the wild. We have investigated the effects of acute temperature change on cardiac function in yellowfin tuna (Thunnus albacares) using an in situ perfused heart preparation. We found that as temperature was reduced, heart rate fell but stroke volume increased. Heart rate exhibited a Q10 of 2.0 between 15fC and 25fC while stroke volume showed a Q10 of –0.5 over the same range. Cardiac output was 15–30% lower at 15fC than at 20fC or 25fC. Maximal output pressure attainable without flow compromise remained nearly constant at 12 kPa over this temperature range. This reduction in cardiac performance with decreasing temperature suggests that cold water may reduce blood flow and hence oxygen delivery in wild yellowfin tuna.
4.5 BLOB, R.W.*, PACE, C. M., WESTNEAT, M.W., Field Museum, Chicago, IL. Testing functional correlates of habitat specialization: swimming and walking in spiny softshell and slider turtles.
Although many freshwater turtles frequently travel long distances over land, several species are morphologically specialized for swimming and spend little time out of water. To test the impact of locomotor specialization on limb kinematics and motor control, we used EMGs and high-speed video to compare hindlimb motor patterns during swimming and walking in the generalized turtle Trachemys scripta (red-eared slider) and the aquatic specialist Apalone spinifera (spiny softshell). Kinematic distinctions between the species indicate that aquatic specialization need not impede terrestrial locomotion. For instance, in both swimming and walking, femoral excursion is nearly twice as great in softshells (70–75f) as in sliders (35–40f). However, in softshells the knee is held significantly straighter during walking than during swimming, suggesting that softshell knee extensors may operate at shorter lengths less optimal for force generation during walking. Motor patterns of softshells and sliders also show several differences; however, the modulation of motor patterns between swimming and walking is similar in both species. In both sliders and softshells, the knee extensor femorotibialis shows a second burst during walking that correlates with a protractive phase of knee extension. In addition, the timing of femoral protractor activity does not change significantly between swimming and walking in either species.Together, our analyses of hindlimb kinematics and muscle activity in these species suggest that measurements of muscle length changes may indicate key distinctions in how habitat specialists and generalists modulate muscle function between behaviors. NIH 5F32NS10813-01/02 to RB and ONR N000149910184 to MW.
P1.54B BLOOM, A. J., SMART, D. R., NGUYEN, D. T., University of California, Davis. Elevated carbon dioxide concentrations inhibit nitrate assimilation in wheat shoots.
Fluxes of CO2 and O2 from the shoots of wheat (Triticum aestivum) demonstrated that exposure to elevated CO2 concentrations strongly inhibited shoot NO3- assimilation. Accordingly, elevated CO2 concentrations enhanced shoot growth of wheat plants receiving NO3- nutrition to only half the extent of plants receiving NH4+ nutrition, and elevated HCO3- concentrations interfered with the translocation of NO2- into wheat and pea chloroplasts. If CO2 inhibition of NO3- assimilation were common among species, it would provide a mechanistic explanation for several responses of plants to elevated CO2 including photosynthetic acclimation to CO2, CO2 inhibition of respiration, and intraspecific and interspecific variation in plant growth under elevated CO2.
54.4 BOETTGER, S.A.*, MCCLINTOCK, J.B., University of Alabama at Birmingham. The effects of organic and inorganic phosphate on muscle contraction and acetyl cholinesterase activity of the nearshore echinoid Lytechinus variegatus.
Lytechinus variegatus is a common nearshore sea urchin that is exposed to phosphate pollutants. Sea urchins were collected in April, 2000 from Saint Joseph's Bay in the northern Gulf of Mexico. Individuals were divided into a control (artificial sea water), sea water containing three concentrations of inorganic (sodium phosphate); or three concentrations of organic (triethyl phosphate) phosphate. Individuals were maintained for an 8-week period, dissected and the Aristotle's lantern retractor muscles extracted individually. Each muscle was attached to a strain gage, stimulated electrically, and muscle contractions (g force/mm muscle length) recorded. When compared to the control group, force of contraction increased significantly in individuals maintained in increasing concentrations of both phosphates. Following the direct coloring thiocholine assay, acetyl cholinesterase activity was assessed by embedding and staining retractor muscles from the Aristotle's lantern, tube-feet, and gut, and counting the occurrence of fully-stained motor endplates/ mm2. Acetyl cholinesterase activity in these same muscles was also assessed through a colorimetric assay. The number of fullystained motor endplates and the enzymatic activity of acetyl cholinesterase decreased in individuals maintained in increasing concentrations of organic phosphate when compared to the control group. No change occurred in individuals exposed to inorganic phosphate. These results indicate that while phosphate exposure has a significant effect on muscle contraction in Lytechinus variegatus, the inhibition of acetyl cholinesterase, an enzyme critical to muscle relaxation, can only be a potential contributing factor in individuals maintained in organic phosphate.
P1.80BOILY, P.* P., KNIGHT, F.M., University New Orleans, LA, University of the Ozarks, AK. Cold-induced hyperthermia and maximum metabolic rate in the nine-banded armadillo.
In response to cold temperature exposure, the nine-banded armadillo (Dasypus novemcinctus) undergoes an increase in metabolic rate concomitant with an increase in core temperature above thermoneutral values.This physiological response is incompatible with standard models of the control of body temperature in non-hibernating mammals where a negative feedback system inhibits heat production if core temperature rises above the setpoint. One possible explanation for this cold-induced hyperthermia is that resting armadillos are slightly torpid and that cold exposure causes the animals to arouse and increase their core temperature to a higher setpoint in order to increase metabolic heat production capacity. We tested this hypothesis by exposing armadillos to cold temperatures while simultaneously gas exchange rates (VO2 and VCO2) and core temperature at four locations (rectal 8cm and 16cm; esophageal 8cm and 16cm). Core temperatures were highly correlated to each other and changed during cold exposure according to the same pattern, thus indicating that cold-induced hyperthermia truly reflects a change in the internal heat content of the animal rather than a decrease in the size of the core. Peak VO2 occurred approximately at the same time as peak core temperatures, thus supporting the hypothesis that cold-induced hyperthermia favors high metabolic rates. Peak VCO2 often occurred well after the peak in core temperatures, when animals were hypothermic. This is likely the result of increased CO2 excretion resulting from the buffering of lactate by bicarbonates rather than an increase in the rate of CO2 production. Funded by NSF (IBN-9723065 and ROA suppl.).
P2.66BOLDUC, M.*, BLIER, P.U., DUTIL, J.D., University du Quebec, Rimouski, University du Quebec, Rimouski, Government of Canada, Fisheries and Oceans. The impact of mitochondial thermal sensitivity on the swimming capacity of Arctic charr.
The swimming performance of fish lies on there capacity to convert chemical energy into mechanical energy, trough the contraction of axial muscle. During sustained swimming, ATP required for contraction is mostly supplied by mitochondrial metabolism. Oxygen consumption is thus proportional to work intensity. At low temperature, the aerobic capacities of fish decrease, as well as maximal sustainable swimming speed. However, for many species cold acclimation increases the aerobic capacity of muscle trough an increase of mitochondrial volume-density and/or of mitochondrial enzymes concentration. This compensation suggest that swimming capacities impairment at low temperature is related to a decrease in mitochondrial catalytic capacities. To test this hypothesis, the aerobic scope for activity of Arctic charr (Salvelinus alpinus) was measured at four different temperatures (1, 6, 12 and 18 C). In each fish, mitochondria were extracted from red muscle of one side of the fish. Mitochondrial respiration (pyruvate and malate as substrates) was measured under the same temperatures. Cytochrome c Oxidase activity was assayed in the mitochondrial preparation and in whole red muscle of the other side of the fish. This allowed us to estimate maximal mitochondrial respiration rate in fish red muscle and compare it to aerobic scope for activity under different temperatures.
P1.94 BONINE, K.E.*, GLEESON, T.T., GARLAND, T. Jr., University of Wisconsin, Madison, University of Colorado, Boulder, University of Wisconsin, Madison. Phrynosomatid lizards show parallel variation in sprint speed and muscle fiber-type properties.
Phrynosomatids are comprised of 3 distinct subclades ((sand lizards, horned lizards), Sceloporus group)) that exhibit great variation in habitat, behavior, and general body plan. This family also varies widely in maximal sprint speed; sand lizards are exceptionally fast, horned lizards are slow, and the Sceloporus group is intermediate. These differences are paralleled by relative hindlimb span (Bonine and Garland 1999, J Zool Lond 248:255–265). We examined the iliofibularis (IF) muscle to determine if fibertype composition varies similarly. Sampling 11 species (44 indivs.), we used histochemical assays for myosin ATPase (fast-twitch capacity) and succinic dehydrogenase (oxidative capacity) to classify fibers as fasttwitch glycolytic (FG), fast-twitch oxidativeglycolytic (FOG), or slow-twitch oxidative (SO). Sand lizards have a high proportion of FG fibers (mean 67%) and a low proportion of FOG (29%); horned lizards have lower FG (28%) and higher FOG (61%); members of the Sceloporus group, which are presumed to reflect the phrynosomatid ancestral state, are intermediate for both FG (45%) and FOG (44%). Across all 11 species, %FOG and %FG are strongly negatively correlated (r = –0.95). Analysis with phylogenetically independent contrasts indicates that this relationship is entirely attributable to the divergence between sand and horned lizards. Neither the proportional area of the IF in the hindlimb, nor the cross-sectional areas of FG (11 spp. mean 417 Mµm2, s.e. adj. for body mass 13.8 [mean log body mass 1.0045]), FOG (260, 9.5), and SO (137, 12.5) fibers, differ among the 3 subclades. However, mass-adjusted hindlimb cross-sectional area is lower for horned lizards. [NSF Grad. Fellowship KEB, NSF IBN-9724140 TTG, IBN-9723758 TG]
56.2BOORSE, G.B., DENVER, R.J.*, University of Michigan.Changes in hypothalamic corticotropin-releasing hormone (CRH) content during environmentally-induced metamorphosis in the Western spadefoot toad (Spea hammondii).
Western spadefoot toads (Spea hammondii) are desert dwelling amphibians whose tadpoles can accelerate metamorphosis as their ponds dry, thereby escaping desiccation. Corticotropin-releasing hormone (CRH) may transduce the environmental signal into an endocrine response that drives metamorphosis.To further understand the role that CRH plays in environmentallyinduced-metamorphosis we developed and validated a CRH radioimmunoassay (RIA) to monitor changes in hypothalamic CRH content following exposure to low water in the laboratory. We generated a rabbit polyclonal antiserum against synthetic Xenopus laevis CRH. This RIA detects vertebrate CRH peptides with high sensitivity and shows low cross-reactivity with the CRH-like peptides sauvagine, urotensin and urocortin. Molecular cloning of the S. hammondii CRH cDNA shows that the sequence of the mature peptide is identical to the Xenopus sequence. Thus, this RIA is homologous for both X. laevis and S. hammondii. We validated the CRH RIA for measurement of peptide content in acid hypothalamic extracts. We demonstrate that CRH-binding protein (CRH-BP), which could potentially interfere with the RIA, is present in S. hammondiibrain. However, very little biologically active CRHBP remains after the acid extraction. Addition of varying amounts of recombinant mouse CRH-BP to the standard curve in the RIA shows that, while the BP can interfere at higher concentrations, the amount remaining after acid extraction does not interfere with the CRH RIA. Using this RIA, we show that S. hammondii tadpoles exposed to low water level exhibit brain-region specific changes in CRH content. (Supported by NSF grant IBN9974672 to RJD and a NSF predoctoral fellowship to GCB)
P1.77BORRELL, B. J.*, LADUC, T.J., DUDLEY, R., University of Texas, Austin. Physiological cost of head-body temperature differences in snakes.
Head-body temperature differentials observed in reptiles and other ectotherms may be important for central nervous system functioning, but the maintenance cost of this differential in terms of water loss has never been studied. Using infrared themography, we measured head-body temperature differentials in three snake families: viperids, colubrids, and boids. Some snake taxa maintain a temperature differential greater than 3 degrees C via respiratory cooling. We estimate the physiological cost associated with such water loss andcompare these costs among clades and habitats. We also discuss the benefits of respiratory cooling in terms of the thermoreceptive capabilities of boids and viperids.
48.3 BOSTWICK, K.S., University of Kansas. Sexual selection for wing-sounds associated with convergent wing shape evolution between three clades of manakins (Aves: Pipridae).
Males of most of the 40 species of Neotropical manakins (Aves: Pipridae) perform energetic courtship displays on lek territories. In nearly half of the speices, males produce mechanical wing sounds during these displays. Recent phylogenetic hypotheses indicate wing sound production may have evolved as many as three times independently in the family. Repeated evolution of mechanical sounds allows comparative analysis of wing morphology in relation to sound production. Specifically, this research addresses (1) if wing shape has been detectably modified in the mechanical sound producing lineages, and (2) if so, are there any commonalities in shape change between lineages. I measured the lengths and widths of 4 wing bones for 42 species of manakins and allies, including representatives from each of the three mechanical sound producing clades. Three measures of overall body size were also made. Wing shape was characterized by the second principle component of a PCA, and mechanical sounds were categorized according to complexity, loudness, and repertoire sizes of species. Independent contrast of species values of these variables were regressed to show that wing shape has changed convergently in mechanical sound producing lineages. Wings of mechanical sound producing clades have shorter, thicker ulna, shorter carpometacarpi, and thicker scapula blades then non-mechanical sound producing manakins. These result support the hypothesis that sexual selection has caused wing morphology to evolve in response to functional requirements for mechanical sound production.
P1.21BOSWORTH, C.A.*, REES, B.B., University of New Orleans, Louisiana. Patterns of protein expression in zebrafish muscle during hypoxia.
Alterations of protein expression may be important in determining the capacity of an organism to tolerate low oxygen concentrations. Most previous studies of fish exposed to hypoxia have examined changes in individual proteins. Here, we report on the use of two-dimensional electrophoresis (2DE) to investigate the effects of hypoxia on patterns of global protein expression in the zebrafish, Danio rerio. Zebrafish were held for 48 h in water having a dissolved oxygen concentration of 10% of the air-saturated value, a treatment known to increase the survival time of zebrafish during more severe hypoxia. Proteins from white muscle were solubilized, separated by 2DE, and stained with silver. Among the proteins resolved was a relatively prominent 50 kDa polypeptide that appeared to have at least 2 isoforms differing in isoelectric point (pI). The relative abundance of the 2 forms was altered by hypoxia, with the more basic form predominating in extracts prepared from hypoxic fish. This change in pI is consistent with post-translational modification, perhaps dephosphorylation, of the protein during hypoxia. The polypeptide is similar in size and pI to mammalian pyruvate kinase (PK), an enzyme known to be regulated by reversible phosphorylation. A change in phosphorylation state of zebrafish PK during hypoxia could result in a more active enzyme at physiological substrate concentrations and contribute to an increased capacity for glycolytic ATP generation during hypoxia. Supported by National Science Foundation grant IBN 9723050.
66.3 BOTTON, M. L.*, LOVELAND, R. E., Fordham University, Rutgers University The diminishing abundance of horseshoe crabs in Delaware Bay: potential impacts on migrant shorebirds.
Migratory shorebirds on staging areas typically concentrate their feeding on unusually abundant prey species, enabling them to rapidly increase mass prior to the next leg of their migration. Delaware Bay is the most important staging area on the Atlantic coast of North America for shorebirds during their Spring (northward) migration; here, birds primarily feed upon horseshoe crab eggs on sandy intertidal beaches. The commercial fishery for horseshoe crabs, which collects the animals for bait in eel and whelk traps, expanded substantially from about 1990 to 1996. Based on surveys of six Delaware Bay, NJ beaches, horseshoe crab egg abundance has decreased in conjunction with the expansion of this fishery. During the period 1985–1991, relatively few surface sediment samples (0 to 5 cm depth) contained zero horseshoe crab eggs, and at least 30% of these samples contained >10,000 eggs per square meter. In contrast, in the period 1996–1999, the frequency distribution is strongly shifted toward the lower egg density intervals. The likelihood of a shorebird encountering surface sediments with zero eggs has increased from about 10% in 1985 to over 50% in 1999. These trends in egg density are also corroborated by significant decreases in the abundance of stranded horseshoe crabs over the period 1978–1999. Shorebirds in Delaware Bay may be adversely impacted by further decreases in the horseshoe crab resource, by extending foraging time and/or intensifying intra- and interspecific competition for eggs.
P3.94 BOWDEN, R.M.*, EWERT, M.A., LIPAR, J. L., NELSON, C. E., Indiana Univeristy, Bloomington. Hormones in yolk layers and offspring sex ratios vary seasonally in turtles.
The presence of hormones in yolks of freshly laid eggs has recently been described in reptiles. These hormones are probably of maternal origin. Their potential to influence offspring sex may be enhanced by temperature-dependent sex determination. Profiles of circulating hormones have been described for several temperate turtles. There appears to be a general pattern to the seasonal oscillations in testosterone (T), progesterone (P), and estradiol (E2). To determine whether this pattern is represented in egg yolks, we measured T, P, and E2 concentrations via radioimmunoassay in three layers of yolk from eggs of early and late nesting female painted turtles (Chrysemys picta). Also, we extracted small yolk biopsies to measure T and E2. We compared the hormone concentrations from the biopsied eggs to the sex ratio of their clutchmates to determine whether maternally-derived yolk hormones influence offspringsex. T and P concentrations were highest in the exterior layer of yolks and E2 concentrations were lowest. The same layered pattern of hormones occurred in red-eared sliders (Trachemys scripta elegans). Yolk E2 concentrations varied seasonally in painted turtles, with low levels in all yolk layers early in the nesting season and higher levels in all layers later on. Neither T nor P exhibited significant seasonal variation. In the yolk biopsies, there also was seasonal variation in E2, but not in T. We found a significant correlation with sex ratio for E2, but not for T.
6.5 BOYLE, H.J.*, GRAHAM, J.B., University of California, San Diego. Acquisition of characters facilitating amphibious behavior in the oxudercine fishes.
The evolutionary sequence of character acquisition associated with amphibious air breathing and terrestrial life was examined in the oxudercine fishes (Gobiidae). Included among the 10 genera (35 species) of oxudercines are forms with little to no specializations for amphibious life as well as the four genera (25 species) of the amphibious, air-breathing mudskipper clade. Five characters hypothesized to be associated with amphibious life (presence of a flattened eye lens, reduced gill surface area to mass ratio, increased buccal chamber volume to mass ratio, inability to repay an oxygen debt in water after exercise, and presence of an air phase inside the burrow) are expressed in one mudskipper species, Periophthalmodon schlosseri. Mapping of the character states of six genera (Oxuderces, Pseudapocryptes, Scartelaos, Boleophthalmus, Periophthalmus, and Periophthalmodon) onto a cladogram generated using morphological data indicates the following evolutionary sequence for the transition from an exclusively aquatic existence to amphibious life: deposition of air inside the burrow, increased buccal chamber volume to mass ratio, decreased gill surface area to mass ratio, loss of a round lens, and loss of the capacity to repay an oxygen debt in water after exercise. The hypothesized sequence of acquisition of morphological, behavioral, and physiological characters demonstrates the evolution of progressive specializations for an amphibious existence in the mudskipper clade. (supported by NSF-9604699)
34.2 BRADLEY, T.J., University of California, Irvine. The discontinuous gas exchange cycle in insects may serve to reduce oxygen supply to the tissues.
The discontinuous gas exchange cycle (DGC) in insects, consists of a closed phase (C) during which the spiracular valves at the openings of the tracheae are closed, a flutter phase (F) when the spiracles open and close rapidly, and an open phase (O) in which the spiracles are open, allowing the free exchange of respiratory gases between the tracheal lumen and the outside air. Early workers such as Buck and Levy & Schneiderman, suggested that the DGC serves to reduce respiratory water loss. More recently, Lighton has suggested that the DGC serves to increase internal carbon dioxide concentrations, thereby facilitating the release of carbon dioxide into environments, such as underground burrows, which are rich in this gas. We have been conducting studies using the Hemipteran Rhodnius prolixus, an insect that takes a bloodmeal up to ten times its previous body volume. In the days following feeding, the insect remains completely still, yet its metabolic rate increases up to 14-fold. We have been using this unusual behavior to examine the effects of metabolic rate on the DGC. We found that the spiracles appear to close very tightly when metabolic rates are low, but do not close fully when the rates are higher. We will present data from other laboratories that demonstrate similar effects when metabolic rate is varied by temperature or when oxygen tensions are manipulated. I propose that the DGC may serve to reduce the supply of oxygen to the tissues during periods of low metabolic rate. Oxygen is toxic to cells, even at ambient concentrations, and insects may use the DGC to provide adequate gas exchange while reducing oxidative damage to tissues during periods of reduced oxygen demand. Supported by NSF grant IBN 0079501.
P2.88 BRAINERD, E.L., LANDBERG, T.*, University of Massachusetts, Amherst. Ventilatory mechanics of an elongate aquatic salamander: Amphiuma tridactylum.
We investigated the mechanism of lung ventilation in an aquatic salamander, Amphiuma tridactylum. Breathing episodes, which occur at intervals ranging from less than 1 to 50 min, are characterized by a single large exhalation followed immediately by a variable number of buccal pumps which refill the lungs. Unlike the majority of salamanders which use a two-stroke buccal pump, Amphiuma uses a four-stroke buccal pump. Four-stroke breathing is also found in another aquatic salmander (Cryptobranchus), in an aquatic frog (Xenopus), and in basal rayfinned fishes (eg. Amia and Lepisosteus), and probably evolved independently in all of these taxa. In Amphiuma, the combination of relatively large tidal volumes and a four-stroke buccal pump results in highly effective exchange of pulmonary gases with the environment. Electromyography of the M. transversus abdominis (TA), abdominal pressure measurements and blow-hole pneumotachography indicate that both passive and active mechanisms contribute to exhalation. Exhalation generally begins in the absence of abdominal muscle activity. This "passive" phase of exhalation may be driven by tissue elasticity, hydrostatic pressure, and/or smooth muscle contraction in the lungs. In most breaths, the passive phase is followed by an active phase in which an increase in pleuroperitoneal pressure, powered by activity in the TA, joins the passive exhalation mechanisms. The use of hypaxial mucles to power active exhalation has now been found in five salamander families (Sirenidae, Cryptobranchidae, Proteidae, Ambystomatidae, and Amphiumidae), providing evidence that aspiration breathing in amniotes may have evolved in two stages: first active exhalation only and subsequently the addition of active inhalation.
6.2 BRAINERD, E.L.*, MURRAY, S. S., University of Masachusetts Amherst. Patterns of genome size evolution in tetraodontiform fishes.
We used flow cytometry to measure genome size (pg of DNA per diploid cell) in 15 species belonging to 7 tetraodontiform families and subfamilies. Previous workers have found that members of Tetraodontidae (smooth puffers) have the smallest genome size of any vertebrate measured to date (0.8 pg vs. a mean of 2.0 pg for all teleosts). We found that this tiny genome is present in members of both tetraodontid subfamilies indicating that the primitive condition for Tetraodontidae was a genome size of 0.8ñ0.9 pg. In contrast, Diodontidae (spiny puffers, sister group to Tetraodontidae), possess a genome which is about two times larger (1.60 pg). Mola mola, a member of the sister group to Diodontidae+Tetraodontidae, also does not have a particularly small genome (1.70 pg). The most parsimonious explanation for this pattern is that the primitive condition for Molidae+ (Diodontidae+Tetraodontidae) is a genome size of 1.60ñ1.70 pg, indicating that the tiny genome size of smooth puffers is a derived character unique to tetraodontids. Previous workers have proposed that the loss of anatomical parts in puffers (no ribs, no pelvis, few vertebrae) might be related to the loss of genetic material in these fishes. Our results do not support this hypothesis because molids and diodontids are missing just as many bits and pieces as smooth puffers, yet they do not have particularly small genomes. We propose that the smooth puffers are a good model system in which to study the evolutionary mechanisms of genome size reduction because: (1) they have an exceptionally small genome; (2) their closest outgroups have much larger genomes; and (3) a smoothpuffer, Fugu rubripes, is being used as a model organism for gene identification and molecular tools emerging from this work will be useful in studies of genome size evolution in these fishes.
28.1 BRAMBLE, D.M.*, LIEBERMAN, D.E., DALEY, M.A., University of Utah, Salt Lake City, George Wash. University, Wash. D. C., Harvard University, Cambridge. Mechanics of head-neck stabilization in running humans: implications for hominid evolution.
Adequate head-neck stabilization ought to be vital to any running mammal but the phenomenon has been little studied. We investigated the mechanical basis of craniocervical stability in humans during treadmill walking and running. Quantitative measures of head-neck and arm motion were obtained from high-speed videography as well as surface mounted accelerometers. Corresponding activity patterns in the trapezius and biceps muscles were also monitored. Our findings show that the mechanical interactions between the head-neck complex and arms are strikingly different in the walk and run regardless of speed. The timing of trapezius muscle activity relative to the step cycle differs in the two gaits (i.e., initiated at midstance in walking vs. heelstrike when running). During running the mass of the arms appears to be coupled to the craniocervical complex through the superior trapezii and the associated nuchal ligament. Indeed, the combined kinematic, kinetic, and electromyographic profiles suggest a biomechanical model in which the momentum of the runnerís arms is used to counteract the tendency of the head and neck to pitch forward at each footstrike. The same, gaitspecific, mechanical linkage may also help to reduce impulsive loading of the head when running (as compared to fast walking). Analyses of occipital morphology in Recent and fossil crania suggest that this novel mechanism, in which the nuchal ligament is a key player, may be unique among hominoids to the genus Homo, thus providing evidence of specialization for running late in human evolution.
P2.33 BRANTLEY, S.*, HILL, P.S.M., University of Tulsa, OK. Lekking in Gryllotalpa major, the prairie mole cricket: a test of the "hotshot hypothesis."
Gryllotalpa major is a rare, burrowing insect indigenous to the tallgrass prairie of the south-central United States that is known to lek during mating. This study looked at possible reasons for the lekking behavior in this species. The "hotshot hypothesis" states that males congregate around a male that has certain traits that make him more preferred by females during mate selection. In aggregating around the favored male, other males increase their own chances of mating. During the mating season, prairie mole cricket males build specialized burrows from which they project their mating call into the air. Females flying in the area hear the mating calls and drop to ground level, entering the burrows of males of their choice. Since a male's call is the only thing a female can use in selecting a mate, different aspects of the male's mating song were analyzed in order to pinpoint a preferred trait. One trait that attracted other males to congregate around a "hotshot" male was the amplitude of a male's call. It was observed that males with the loudest call on a particular night would entice other males to their positions to construct their own burrows the following night or the next night that calling occurred. These data support the "hotshot hypothesis" as the reason for lekking in Gryllotalpa major.
S9.14 BREUNER, C. W.*, HAHN, T. P., Arizona State University, University of Alaska Fairbanks. Corticosterone and inclement weather: mechanisms underlying adaptive behavioral responses in mountain birds.
In seasonally-breeding migratory birds, the drive to arrive early and establish a territory on the breeding grounds carries with it the potential benefit of improved reproductive success, but also the risk of encountering potentially life-threatening inclement weather. This is particularly true in species breeding at high elevations or high latitudes. Storms can reduce food availability, limit foraging opportunities, and impose increased thermoregulatory costs. Individuals' reproductive success can thus depend on how effectively they assess risks, and then modify behavior. In the High Sierra of California, mountain white-crowned sparrows (Zonotrichia leucophrys oriantha) typically reach sub-alpine breeding areas in early May, when storms are common. Over the past 6 years, we have shown that when storm conditions become extreme, Z. l. oriantha typically abandon their territories and fly several kilometers to lower elevation, where conditions are milder and food is more abundant. Variation in internal reserves and/or food availability at the breeding site may modify the timing and duration of territory abandonment. We have evidence that corticosterone acts as an endocrine mediator between the environment and behavior during inclement weather. This system is proving ideal for studying the endocrine mechanisms that coordinate dramatic shifts in behavior in response to both external and internal factors. We have developed a working model of how several of these factors (weather, food availability, energy reserves, and corticosterone) interact to affect behavioral decisions.
S10.5 BREZNAK, J.A., Michigan State University, E. Lansing. Phylogenetic diversity and physiology of termite gut spirochetes.
Spirochetes are major members of the termite gut microbiota, accounting for up to 50% of all the prokaryotes present. However, our understanding of them has been meager, as none had ever been isolated in pure culture since first being observed in termite guts over a century ago. By analyzing SSU rDNA clones (obtained after PCR amplification from termite gut DNA), we and others have found that termite gut spirochetes represent novel treponemes. As many as 26 new and different species of Treponema were detected in guts of various individual termite species, implying that earth's termites constitute a rich reservoir of novel spirochetal diversity. Physiological properties that enable spirochetes to assume such abundance in termite guts are not yet clear, but probable roles for spirochetes in termite nutrition are now beginning to emerge from studies of the first pure cultures recently isolated in our laboratory [J. R. Leadbetter et al. (1999) Science 283:686–689]. All strains obtained so far produce acetate as a major fermentation product, with some capable of doing so from H2 + CO2. This latter process, previously unknown in spirochetes, is a significant H2 "sink" and source of acetate in termite hindguts. In addition, all strains possessed at least two homologues of nifH in their genomic DNA and catalyzed N2 fixation, another process heretofore unknown in spirochetes. Microbially-produced acetate is known to be a major carbon and energy source for termites, and N2 fixation by gut microbes can supply up to 60% of the N requirement of some termite species. Hence, with the discovery of acetogenesis and N2 fixation by termite gut spirochetes, we are finally beginning to reconcile the old observation that elimination of spirochetes from the gut results in decreased survival of termites.
S8.5 BROCHU, C. A., Field Museum. Beyond mere morphology: reflections of a computed tomography addict.
Computed tomographic (CT) technology has become a standard method for nondestructively accessing the interior structures of irreplaceable fossils. This vastly increases the informative power of fossils and allows researchers a unique opportunity to visualize internal features in three dimensions, either through three-dimensional reconstruction or as animations of sequential slices. Either mode (2-D or 3-D) can bring new insight into the study of fossil organism morphology, whether the focus is phylogenetics, functional morphology, physiology, or any other research program. There are additional practical applications of CT imagery to fossil preparation and the tracing of post-collection human modification. CT imagery improves the researcher's ability to illustrate complex internal structures, both to the research community and the general public. The data can be published in its native digital format, either over the World Wide Web or through media such as CD-ROM or DVD, effectively allowing the dissemination of "virtual specimens". Simple software applications allow colleagues, teachers, and students to interact with the data. Digital anatomical atlases can be generated for a broad diversity of taxa, which gives instructors and students a larger sample of available study specimens. One such atlas has already been made available for Alligator mississippiensis. Application of CT imagery to popularly-known taxa, as was recently done with Tyrannosaurus rex, gives researchersa new means of making important-morphological and evolutionary points to the general public. Nonavian dinosaurs are inherently interesting to people, and a host of evolutionary questions, from the anatomy of pneumatic structures in the skull to origin of birds, can be addressed through a combination of careful phylogenetic analysis and CT imagery. This lets scientists highlight principles common to all comparative biologists to the public.
63.2 BRODIE, R.J., Smithsonian Marine Station at Fort Pierce. Ontogenetic changes in rates of water loss and shell-wearing behaviors enable land hermit crab megalopae to avoid desiccating in air.
The land hermit crab, Coenobita compressus, migrates from sea to land during the megalopal stage of postlarval development. As the megalopa emerges onto land, it encounters a physical environment wholly different from that of the sea. I investigated changes in C. compressusí behavior and physiology that enable it to avoid desiccation on land. In one experiment, I examined changes in rates of water loss before, during, and after megalopae were able to settle on land to determine if their resistance to desiccation improved over time. I found that megalopae became increasingly resistant to desiccation with age. In the second experiment, I exposed megalopae with and without snail shells to relative humidities of 100, 92, 85, and 76 % to determine if the shell would increase survival in the lower humidity environments. Megalopae wearing shells were far more likely to survive the two lowest humidities compared to their naked counterparts. Thus, behavioral and morphological enhancements to desiccation resistance facilitate the land hermit crabís transition to land.
S1.5 BROWNELL, P.H.*, VAN HEMMEN, J.L, Oregon State University, Corvallis, Technical University, Munich. Vibration sensitivity and prey-localizing behavior of sand scorpions.
As burrowing, nocturnal predators of small arthropods, sand scorpions have evolved exquisite sensitivity to vibrational information that comes to them through the substrate they live on -dry sand. Over distances of a few decimeters, sand conducts low velocity (50 m/sec) surface (Rayleigh) waves of sufficient amplitude and bandwidth (fmax 350 Hz) to be biologically detectable. Eight acceleration-sensitive receptors (slit sensilla) at the tips of the scorpion's circularly arranged legs detect surface vibrations generated by prey movements or ‘juddering’ signals from other scorpions. From this input alone, target direction is accurately calculated up to 20 cm distance. By ablating slit sensilla in various combinations on the eight legs, the contribution each makes in computing target location can be assessed. Other behavioral experiments show that differential timing of surface wave arrival at each sensor, and not relative amplitude of stimulation, is the cue that determines target location. A computational theory to account for wave source localization has been developed using a population of second-order neurons, each receiving excitatory input from one sensor and inhibition from a triad of sensors opposite to it in a circular, eightelement array. Input from a passing surface wave opens a time window whose width determines the firing probability of second-order neurons. Stochastic resonance (optimization) tunes the relative strengths of excitatory and inhibitory inputs to second-order neurons, and target direction is encoded as the relative excitation of cells within the population. The excellent agreement between theory and behavioral observations confirms the mechanistic simplicity of the sand scorpion's sensory system for computational mapping of vibration source location.
S10.9 BRUNS, T.D.*, BIDARTONDO, M.I., TAYLOR, D. L., University California, Berkeley. Interactions of ectomycorrhizal fungi and ectomycorrhizal epiparasites.
We have studied non-photosynthetic plants in the Monotropoideae and Orchidaceae that obtain their fixed carbon from surrounding photosynthetic plants through shared ectomycorrhizal fungi. These "epiparasites" are only indirectly connected to surrounding trees, which are the ultimate source of their carbon; their proximal hosts are fungi that are mutualistically associated with the trees. We found that all epiparasitic plants have specific fungal associations, which in somecases exhibit geographic mosaic patterns. In two species, Sarcodes sanguinea and Pterospora andromedea, seed germination is stimulated by diffusible compounds from the fungi associated with the adult plants, but not by distantly related fungi. Thus, the first step in establishment of these specific interactions is based on a specific plant reaction to the presence of its fungal host. This fact, coupled with localized seed dispersal, has parallels with insect host-fidelity systems and may facilitate hostrace formation, which we now have evidence for in Corallorhiza species. In nature, S. sanguinea appears to increase the presence of its host fungus, Rhizopogon ellenae, and the abundance of Abies magnifica roots to which the latter is associated. This either provides an unusual case of parasite-induced host-hypertrophy, or alternatively it suggests an unexpected mutualistic aspect to this symbiosis.
S2.4 BRYANT, S.V., University of California. Regeneration: something old; something new.
Urodeles are unique among vertebrates in their ability to regenerate lost appendages as adults. Evidence from numerous studies indicates that regeneration is a biphasic process, with the first phase involving the transition to a blastema, and the second involving the control of growth and pattern formation within the regeneration blastema. Patterns of gene expression in the first phase mark it as unique and distinct from limb development. In the second phase, patterns of gene expression and tests of gene function, suggest mechanisms that are common to both development and regeneration. It is the genes expressed during the early, unique phase that transform differentiated limb cells into a blastema with similar properties to that of an embryonic limb bud, thereby making regeneration possible. Recent advances in somatic cell transgenesis in the axolotl are allowing for the functional analysis of the molecules controlling the transition into dedifferentiation, and will eventually lead to therapeutic interventions to stimulate human regeneration.
53.4 BUCHANAN, J. S.*, CRANFORD, J. A., Colorado State University, Fort Collins, Virginia Polytechnic Institute and State University. Changes in energy utilization, food processing, and gastrointestinal morphology of voles under differing environmental conditions.
Meadow voles (Microtus pennsylvanicus) are small herbivores that are active year-round, yet have no capacity for torpor. Their food supply, though abundant, may be of low quality when plants undergo winter senescence. Therefore, they must adjust their food intake rate and/or modify their gastrointestinal morphology in order to obtain the energy necessary to meet increased demands during winter. We performed an experiment of factorial design, consisting of 112 meadow voles, each assigned to one of eight trials, placed under the conditions of high (50% NDF) or low (5% NDF) dietary fiber, high (21 C) or low (5 C) temperature, and long (16L:8D) or short (8L:16D) photoperiod to determine which of these environmental variables was most responsible for eliciting the behavioral or morphological changes required for meadow voles to survive the winter. Meadow voles increased food intake and decreased dietary turnover time under the most demanding environmental conditions. Consequently, they were able to compensate for their increased energy demands by increasing food intake and decreasing dietary turnover time, and made only minimal changes to their gastrointestinal morphology. Dietary fiber level was the most important factor in eliciting these changes in intake rate, followed by ambient temperature and daylength, respectively. There were significant interactions between the three factors and all play an important role in bringing about the changes necessary for meadow voles to endure harsh winter conditions.
S14.8 BUCHHOLZ, D.*, HAYES, T., NIH, University of California, Berkeley. Evolution of diversity in anuran tadpoles: accelerated metamorphosis in spadefoot toads.
Spadefoot toads exhibit a large diversity in larval period and size at metamorphosis. We used growth and development data to examine evolutionary, physiological, and morphological aspects of this diversity. To obtain comparable data across taxa, we reared tadpoles under laboratory conditions from all spadefoot toads and one parsley frog. Differences in growth and development suggested physiology, rather than phenotypic plasticity, explained larval period diversity. Mapping larval data onto a molecular phylogeny indicated that rapid metamorphosis originated within the spadefoot toad family. To understand the physiological basis for accelerated metamorphosis, we used radioimmunoassay to estimate thyroid hormone levels throughout prometamorphosis and climax in Scaphiopus couchii, Spea multiplicata, and Pelobates syriacus. We also used an in vitro tail tip assay to measure tissue sensitivity to thyroid hormone. The higher thyroid hormone levels and the higher sensitivity of the tail in vitro in Sc. couchii correlated with its shorter larval period length. We examined the relationship between larval period length and gonad, spade, and thyroid develoement. Gonads and spades differentiated earlier in stage in Pelobates compared to Spea and Scaphiopus. In contrast, thyroid gland differentiation correlated with larval size rather than larval period length. In conclusion, the differences in thyroid physiology across taxa may be endocrinological mechanisms underlying accelerated metamorphosis. Also, because morphological development during metamorphosis is affected by thyoid hormone, physiological evolution to shorten larval period in New World spadefoot toads may have had heterochronic side-effects in spadefoot development.
P3.107 BUCK, C.L.*, BARNES, B.M., University of South Dakota, University of Alaska Fairbanks. Influence of staged encounters on testosterone and corticosterone in freeliving arctic ground squirrels.
In a field study on the North Slope of Alaska we determined levels of plasma testosterone and corticosterone for male arctic ground squirrels after emergence from hibernation in spring, throughout the mating season, and prior to their immergence into hibernation in late summer. In mid April reproductively active males emerged with testes descended into the scrotum and with intermediate levels of plasma testosterone. Testosterone levels remained constant at 2.9 ± 0.29 ng/ml for about 1 week before significantly increasing to the active season maximum of 4.6 ± 0.42 ng/ml. A lesser peak in late summer of 2.7 ± 0.17 ng/ml not associated with testicular maturation was observed before levels decreased to the annual minimum of 1.7 ± 0.57 ng/ml prior to entrance to hibernation. Corticosterone levels did not vary significantly across season and averaged 4.3 ± 0.10 ng/ml. We tested the responsiveness of plasma testosterone and corticosterone to challenges by conspecific males by staging aggressive encounters between males and comparing plasma levels of these animals to those of unmanipulated animals. The effect of staged encounters on testosterone level depended on time of year. Testosterone levels in spring were significantly up-modulated after a staged encounter and were positively correlated to the relative intensity of the encounter, whereas staged encounters in late summer had no significant effect on testosterone level. Corticosterone levels in both spring and late summer were significantly increased by staged encounters and were positively correlated to the relative intensity of the encounter. These results suggest that circulating levels of testosterone and corticosterone in male arctic ground squirrels are the result of a combination of seasonal and social factors.
S13.10 BUCKLEY, D.P., Quinnipiac University, Hamden CT. Fostering learningcentered experiences with web-based technology.
The scientific literacy of our nation is a concern, but emerging insights about the cognitive development of learning and new educational technologies provide encouragement that we may be engaged in a pedagogical revolution. However, technology is no panacea. Exploiting the learning potential of the web will require the promotion of inquiry-oriented and learning-centered principles, but most web sites are little more than electronic books, with little interactivity and less assessment. Interactivity can promote active learning styles. Assessment tools can provide real-time feedback, incentive systems to facilitate competency-based learning standards, and diagnostic clues about individual learning needs. Learningcentered technology that is beginning to emerge may help us to grapple with one of the worst obstacles to teaching reform: the Coverage Dilemma. Many faculty are wary to spend valuable class time on time-intensive pedagogies. Assessment-rich, web-based instructional technology may allow us to move the authority of learning foundational information to our students on their own time, making room for more important learning goals in class time. The most exciting applications of web-technology may be those that foster student experience in the process of science with research simulations or through access to online data and research tools. However, these more open-ended learning experiences tend to be more leaky pedagogically; not all students are prepared to benefit from these more demanding experiences. Therefore, depending on the sophistication of the students, there may be a need for new instructional designs that provide assessment in new ways in these more demanding, open-ended learning environments. Lastly, we must develop web-based technology that promotes these science education standards for all students, not just for our majors.
P1.47 BUDD, S. J.*, ROER, R.D., KINSEY, S.T., University of N.C. at Wilmington. Energetic cost of osmoregulation as a function of size and salinity in Callinectes sapidus.
In order to determine the energetic cost of osmoregulation in C. sapidus over a range of salinities, adult and juvenile crabs were acclimated to either sea water (1000 mOsm) or dilute sea water (150 mOsm). Oxygen uptake was measured in vivo with intact crabs and in vitro using gills removed from the crab and ligated at the proximal end. Data demonstrated that at each salinity there was a decrease in weight-specific oxygen uptake with increasing body mass and gill mass. Acclimation to dilute medium resulted in an increase in whole-animal oxygen uptake for crabs of all weights relative to that in sea water. Exposure of sea water-acclimated posterior gills to 150 mOsm resulted in a rapid and marked increase in oxygen uptake relative to sea water. Nuclear magnetic resonance spectroscopy on individual gills was able to resolve the relative concentrations of all the major phosphate compounds involved in energy metabolism (arginine phosphate, ATP and inorganic phosphate). Exposure of sea water-acclimated posterior gills to 150 mOsm resulted in a marked decrease in arginine phosphate and an increase in inorganic phosphate.
P2.46 BUDICK, S. B.*, O'MALLEY, D. M., Northeastern University Minimal behavioral deficits are observed after laser-ablation of the nMLF in larval zebrafish.
Larval zebrafish exhibit a range of locomotive behaviors including swimming, turning and escaping. These behaviors are controlled by a relatively small group of brainstem neurons including cells of the nucleus MLF (nMLF) plus reticulospinal, vestibulospinal and T-reticular neurons. Little is known of the function of the nMLF cells, though they constitute perhaps 15% of the total descending motor control system in larval zebrafish. The nMLF cells are suggested to be involved in the initiation of swimming (Bernau et al. 1991; Uematsu and Todo, 1997) and might constitute part of the midbrain locomotor region. Because laserablation is a useful technique for revealing the functional role of individually identified hindbrain neurons (Liu and Fetcho, 1999), we attempted to laser-ablate the nMLF both unilaterally and bilaterally (a minimum of 7 cells/hemisphere), using a 15mW Kr-Ar laser. Larval behavior was then analyzed after a recovery period of at least 24 hours. Spontaneous locomotion, as measured by the number of swim bouts and the total distance swam over 30 minutes, was not effected by ablation. Furthermore, kinematic analysis of high-speed imaging data revealed no major deficits in either the escape-response or swimming. The data do suggest, however that the nMLF may be important for generating high angular velocity, large amplitude escape responses. Occasionally, multiple, spontaneous C-bends occurred in rapid succession. A striking feature of these C-bends was that they resulted in little forward propulsion. Such abnormal C-bends were not observed in control fish. These results suggest that nMLF cells are not necessary for the initiation/control of swimming, but may contribute to the coordination or control of the escape response. Supported by NIH Grant NS 37789.
22.4 BUNDLE, M.W.*, DAIL, K.P., University of Montana, Missoula. The metabolic cost of flight in budgies: revisiting an outlier.
Measuring the metabolic cost of flight has been possible for a little more than thirty years. Since V. A. Tucker's classic work with budgerigars, fewer than a dozen other species of birds have been flown in wind tunnels in order to determine their metabolic rates during flight. Results from these studies portray one of two patterns: either the metabolic cost of flight appears to be independent of flight speed, or the cost of flight appears as a U-shaped curve with increasing flight speed. All but Tucker's study show little increase in metabolic cost across the range of speeds for which data were obtained. In addition to the evidence provided by metabolic data, recent measurements of the mechanical power developed during flight also support the notion that birds are able to fly over a wide range of speeds with little change in the cost of flight. Flight costs in budgerigars should be viewed not as the commonly cited general rule, but rather as the exception. Since Tucker's work stands in such stark contrast to nearly all of the available data on flight costs, we have revisited his experiments in our tunnel, increasing both the sample size and the range of speeds over which the birds have been flown. Four Budgerigars were flown across a range of speeds (4-16 m/s), while wearing a mask in order to collect and analyze their expired air. Our measurements of the metabolic cost of flight agree well with those of Tucker's budgies. This confirmation of the original published pattern suggests that budgies are unlike other species and are unable to duplicate the unknown mechanism that allows other birds to fly with costs that are independent of flight speed. (supported by NSF IBN-0082075)
18.5 BURNAFORD, J. L., Oregon State University. The physiology of positive interactions: effects of shade and season on endogenous levels of hsp70 in field populations of the black chiton Katharina tunicata
Canopy-forming algae can be important to consumers by providing food and protection from predation or intense insolation. In the low rocky intertidal zone of the Pacific Northwest, the chiton Katharina tunicata is closely associated with the canopy-forming alga Hedophyllum sessile. In previous studies, Hedophyllum canopy removal resulted in a dramatic drop in Katharina abundances, but the cause of this decline was not determined. In a three-year field experiment, Katharina numbers were significantly higher in shaded plots (artificial shade or natural Hedophyllum) than in unshaded plots in the spring and summer, but abundances were not different in the fall and winter. During low tide on sunny summer days, Katharina body temperatures are 6 to 9°C warmer in the open than in the shade. These data suggest that the shade provided by the algal canopy is important for reducing heat stress for Katharina. To examine the effect of shade on the physiological state of chitons in the field, I used fences to maintain Katharina under shaded and unshaded conditions from April to November of 1999 and April to August of 2000. From monthly tissue samples of these chitons, I quantified endogenous levels of heat shock proteins (hsp70 isoforms). To examine the effect of seasonal ambient temperature on hsp70 levels, I also collected monthly tissue samples from the unmanipulated Katharina field population from April 1999 to August 2000. These data on seasonal and shaderelated variations in the heat-shock response of Katharina, combined with data from a long-term ecological study, give a unique picture of the interacting effects of physiology and ecology on community structure.
P1.61A BURNESS, G.P.*, YDENBERG, R.C., HOCHACHKA, P.W., University of California, Los Angeles, Simon Fraser University, University of British Columbia. Physiological origin and reproductive consequence of variation in daily energy expenditure: a study of breeding tree swallows.
We studied tree swallows (Tachycineta bicolor) provisioning dependent young to test for relationships among parental daily energy expenditure (DEE), the masses of internal organs/tissues, and indices of breeding success. We predicted: (1) parental DEE would increase with brood size and nestling condition, and (2) adults with high DEE would require large internal organs and high metabolic capacities in their pectoral muscles. We measured the growth rate of nestlings from natural broods of 5, 6 and 7 over a 4-day period, followed by parental DEE using the doubly labeled water technique. Adults were then dissected and internal organs were weighed. As an index of capacity for flux through specific steps in various metabolic pathways, we measured the activity of citrate synthase, pyruvate kinase, HOAD, and lactate dehydrogenase in the pectoral muscle. The growth rate of nestlings was independent of the brood size in which they were reared. This indicated that adults did not trade-off nestling quality for quantity. Despite predictions, parental DEE was also independent of brood size. We hypothesize that adults differed in foraging efficiency and matched their clutch size to their own individual provisioning abilities. Among individuals with the same sized broods, in one of two years there was a positive relationship between DEE and brood mass, suggesting reproductive benefits of an high DEE. There was no relationship between an individual's DEE and the size of any internal organ or the metabolic capacity of the pectoral muscle. Consequently, a previous suggestion that large internal organs allow for the maintenance of high-energy budgets is not supported.
P1.28 BURNETT, K., ILIFF, S., BURNETT, L.*, University of Charleston, SC. Chronic sublethal hypoxia increases susceptibility of Litopenaeus vannamei to bacterial challenge.
Mortality rates of the aquacultured shrimp Litopenaeus vannamei injected with Vibrio parahaemolyticus are significantly increased when the bacterial challenge is accompanied by an immediate shift from well-aerated water to sub-lethal hypoxia (acute hypoxia). A more realistic scenario is that shrimp raised in intensive culture or in natural ecosystems would be exposed for longer periods of time to sub-lethal hypoxia (chronic hypoxia). The present study addressed the possibility that animals might adapt to chronic hypoxia, returning to a more disease- resistant status. Juvenile L. vannamei (1.0 – 1.5 g) were either maintained under normoxia or exposed to sublethal hypoxia (4% O2, 2% CO2 and pH of 6.8–7.0). After seven days animals from both exposure conditions were injected intramuscularly with an LD50 dose (105/shrimp) of V. parahaemolyticus. Both test groups were held under sub-lethal hypoxia for 48 hours and monitored for survival. Mortality rates were compared by a repeated measures two-way ANOVA. Chronic (7 day) hypoxia significantly increased mortality rates in challenged shrimp compared to acute hypoxia. Taken together with our previous studies (Mikulski et al., [2000] J. Shellfish Res. 19:301–311), these data show that both acute and chronic hypoxia increased susceptibility of L. vannamei to bacterial challenge. Furthermore, these shrimp did not successfully adapt to overcome the suppressive effects of hypoxia on disease resistance, rather the animals displayed higher mortality rates with increased time of exposure to hypoxia. (USDA CSREES 99-35204-8555)
P3.1 CAPPOLA, V.A., FAUTIN, D.G.*, University of Kansas. The status of Corallimorpharia (Cnidaria, Anthozoa) based on molecular data from mitochrondrial 16s rDNA and nuclear 28s DNA.
Corallimorpharia is an order of Anthozoa (phylum Cnidaria) that is currently considered equivalent in rank to Scleractinia (hard corals) and Actiniaria (sea anemones). Rather than being an independent order, Corallimorpharia has been hypothesized to be part of Scleractinia or Actiniaria. Morphological evidence supports corallimorpharians as more closely related to scleractinians. Published sequence data for mitochondrial 16S rDNA and nuclear 18S rDNA support the position of corallimorpharians within the scleractinian clade, but data from nuclear 28S rDNA support them being more closely related to actiniarians. Differences in taxon sampling and methods of analysis, and small sample sizes have contributed to problems with comparing among molecular analyses. We sequenced the nuclear 28S ribosomal RNA gene and the mitochondrial 16S ribosomal gene from representatives from most hexacorallian orders. Our preliminary parsimony analyses do not support a corallimorpharian clade. This research was supported by NSF grant DEB95-21819 (PEET) to DGF.
61.4 CARD, G.*,WEYAND, P., BIEWENER, A.A., Concord Field Station, Harvard University, Bedford. Changes in effective mechanical advantage of the human limb during sprint acceleration.
How do people go fast? Previous studies-have examined the role of leg muscle force in relation to energy cost during running at various steady speeds, but few have addressed how the leg muscles contribute to accelerating the body to attain those speeds. We examined humans sprinting from a crouch to top speed. Using a runway with an imbedded force plate and synchronized video data, we were able to determine the effective mechanical advantage (EMA) of the limb at different steps of each subject's sprint acceleration to top speed. EMA is defined as the ratio of limb muscle force to ground reaction force integrated over the time of limb contact with the ground. It was measured at each of the leg joints (hip, knee, ankle) and then averaged for an overall measure. Data from the nine runners measured indicate that, as opposed to steady state running in which EMA does not change with speed, EMA increases slightly as the subject increases speed by accelerating in the first several steps of a sprint. EMA distribution between joints also changes during acceleration, with hip EMA starting low and increasing while knee EMA starts high and decreases. These results imply that during rapid acceleration, more of the force is supplied by hip extensor muscles whereas during steady state running, these muscles have diminished importance and supporting force is generated more by knee extensors. Understanding muscle mechanics during acceleration thus has implications for fiber type distribution at different joints and for better quantifying the mechanics and energetics of free-ranging animals who rarely move at a steady rate.
27.3 CARELLO, C. A.*, SCHEUNMANN, T. L., HEITMANN, D. M., University of Wisconsin-Eau Claire. How body size affects the metabolic efficiency and lower limb joint kinematics of quail running on an incline.
The majority of studies dealing with bipedal locomotion on varying surface grades have focused on humans. Thus, little is known about the relationship between body mass and efficiency of locomotion for running on inclines in non-human bipeds. In order to quantify this relationship in quail we used oxygen consumption analysis to determine the efficiency of incline running in small Button Quail (43g) and large Mountain Quail (211g). We found that Mountain Quail were metabolically more efficient than Button Quail when running uphill. In an attempt to explain the mechanisms responsible for this relationship between body mass and efficiency, we then conducted kinematic analysis-on the hip, knee and ankle joints for level and incline running. We found that the range of motion for extension of all lower limb joints increased on an incline. We also found that there was a relatively greater increase in the extension of the limb joints in the smaller Button Quail when compared to the larger Mountain Quail. Extension of the lower limb joints occurs during the acceleration phase of the step and this is therefore considered the energetically costly phase of the step. Thus, smaller animals incur a reduction in metabolic efficiency because their lower limb joints must undergo a greater range of motion during the most energetically expensive phase of the step.
45.2 CARL, T. F., HANKEN, J.*, Harvard University, Cambridge, MA. Neural-crest derivation of the ossified skull in amphibians revealed by vital labeling with GFP.
Derivation of most if not all of the ossified skull from the embryonic neural crest is an accepted axiom of contemporary developmental biology. Yet, this "fact" is based on direct empirical results involving just one species of vertebrate, the domestic chicken. Anuran amphibians (frogs) pose a particularly difficult challenge in this regard: bone typically forms many weeks after hatching, and tracing individual cells over this lengthy interval is technically difficult. We used RNA encoding for green fluorescent protein (GFP) to label premigratory neural crest in embryos of Xenopus laevis, and assessed cranial derivatives both before and after metamorphosis. Results confirm the neural crest contribution to larval cranial cartilages demonstrated previously by using conventional vital stains, lineage markers, and ablation techniques. They also provide evidence for the neural crest derivation of a major paired skull bone, the frontoparietal; other, later-forming bones are currently under study. This is the first direct empirical demonstration of neural crest contribution to the ossified skull in any amphibian. Supported by NSF.
44.4 CARL, T.F.*, KLYMKOWSKY, M.W., HANKEN, J., Harvard University, Cambridge, MA, University of Colorado, Boulder, Harvard University, Cambridge, MA. Multiple functions for the gene slug in Xenopus laevis.
The neural crest is a distinct population of embryonic cells found only in craniates. Several genes, including BMP-4and the zinc-finger transcription factor Slug, have been shown to mediate neural crest development in both chickens and mice. We examined the function of Slug in the frog Xenopus laevisby injecting antisense RNA (ASR) targeted to the 3' UTR of Xenopus Slug (XSlug). Injection of XSlug ASR inhibits neural crest-cell migration and leads to reduction or loss of many neural crest derivatives, including pigment cells and cranial cartilages. Moreover, regions injected with XSlug ASR show significantly elevated levels of cell death, and expanded regions of the BMP-4 antagonist, Chordin. In addition to its important role in neural crest migration, XSlug may mediate the cell-deathsignaling pathway and other significant developmental pathways in Xenopus laevis. Supported by NSF.
S9.13 CARR, J.A.*, BROWN, C.L., MANSOURI, R., VENKATESAN, S., Texas Tech University, Lubbock. Stress, neuropeptides, and feeding behavior: an evolutionary perspective.
Stress inhibits feeding behavior in all vertebrates. Data from mammals suggest an important role for hypothalamic neuropeptides, in particular the melanocortins and corticotropin-releasing hormone (CRH), in mediating stress-induced anorexia. The effects of CRH on food intake are evolutionarily ancient, as this peptide inhibits feeding in fishes, birds, and mammals. The effects of melanocortins on food intake have been studied only in mammals. Although there is evidence that CRH and the melanocortins influence hypothalamic circuitry controlling food intake, these peptides may have a more primitive role in modulating visuomotor pathways involved in the recognition and acquisition of food. Stress rapidly reduces visuallyguided prey-catching behavior in toads, an effect that can be mimicked by administrationof CRH, while corticosterone and isoproterenol are without effect. Melanocortins also reduce prey-oriented turning movements and, in addition, facilitate the acquisition of habituation to a moving prey item. The effects of these neuropeptides are rapid, occurring within 30 min after administration. Thus, changes in neuroendocrine status during stress may dramatically influence the efficacy with which visual stimuli release feeding behavior. By modulating visuomotor processing these neuropeptides may help animals make appropriate behavioral decisions during stress. Supported in part by a HHMI grant through the Undergraduate Biological Sciences Education Program to TTU.
21.4 CARRANO, M. T., SUNY at Stony Brook. Homology and the evolution of nonavian dinosaur locomotion.
Non-avian dinosaurs diversified throughout the Mesozoic from a single bipedal, parasagittal-limbed ancestor. Their 140-my radiation spanned over three orders of magnitude in body size and included eight major clades. In spite of this, diversification within the dinosaurian locomotor apparatus appears to have been comparatively restricted. I analyzed dinosaur hind limb and pelvic anatomy within a cladistic framework in order to quantify these patterns of change. Using methods to analyze both discrete and continuous characters in a phylogenetic context, I identified where homoplasy constitutes parallelism and might thereby be used to infer similar selective pressures on hind limb function. Finally, I evaluated the resulting phylogenetic patterns in light of terrestrial locomotor biomechanics. These analyses revealed repeated, independent derivations of several morphological features that have potential relevance for hind limb locomotor function. These include anteroposterior expansion of the ilium, medial reorientation of the femoral head, and elevation of the femoral lesser trochanter. Such parallel changes appear to reflect the enlargement of several major hind limb muscles, as well as a trend towards switching their predominant function from abductionadduction to protraction-retraction. The timing of these changes suggests that they occurred subsequent to the initial divergence of Dinosauria into its constituent lineages. In addition, many "avian" characteristics are shared with more basal theropod dinosaurs, and several were acquired convergently in otherdinosaurian clades.
42.3 CARRE-O, C. A.*, NISHIKAWA, K.C., Northern Arizona University, Flagstaff. Does morphology correlate with prey capture kinematics in leptodactylid frogs?
Leptodactylid frogs exhibit diversity of the tongue and jaw mechanics during prey capture. Two mechanisms of prey capture have been seen in leptodactylids: inertial elongation and mechanical pulling. Phylogenetic analyses suggest that inertial elongation has evolved independently from mechanical pulling several times within leptodactylids. The goal of this study is to examine the evolution of feeding mechanisms in this diverse group of frogs. Feeding mechanisms of frogs can be categorized based on patterns of kinematics. The primary kinematic difference between inertial elongation and mechanical pulling is the movements of the tongue and jaw. During inertial elongation, the movements of the tongue and jaw are precisely coordinated, whereas in mechanical pulling, these movements are uncoupled. Leptodactylids that are considered to be inertial elongators tend to have short gape cycles (11 ms), a high velocity of the lower jaw during mouth opening, and a great increase in the length of the tongue (180% of resting length). In contrast, leptodactylid frogs that are defined as mechanical pullers generally have longer gape cycles (28 ms), slower velocity of the lower jaw, and a decrease in the length of the tongue during protraction (40% of resting length). Thus, we expect to find relative differences in the lever system of the jaw between inertial elongators and mechanical pullers. Inertial elongators should have proportionally shorter in-levers in order to maximize the speed of mouth opening, while mechanical pullers should have proportionally longer inlevers in order to maximize the force of mouth closing. The variability in kinematics and morphology among species of leptodactylids may reflect differences in the foraging ecology between species.
21.3 CARRIER, D.R.*, LEE, D.V., WALTER, R. M., University of Utah, Salt Lake City. Influence of rotational inertia on the turning performance of theropod dinosaurs.
Turning agility of theropod dinosaurs may have been severely limited by the large rotational inertia of their horizontal trunks and tails. Bodies with mass distributed far from the axis of rotation have much greater rotational inertia than bodies with the same mass distributed close to the axis of rotation. In this study, we increased the rotational inertia of human subjects 4.6 times, to match our estimate for theropods the size of humans, and measured the subjects' ability to turn. To determine the torque required to execute turns, three subjects performed 45 degree jump turns on a force platform. When the rotational inertia was increased 4.6-fold, the time to push-off increased 1.8-fold and the torque impulse applied to the ground increased 3.76-fold. To determine the effect of the increased rotational inertia on maximum turning capability, five subjects performed jump turns in which they jumped vertically from a standing position and attempted to spin as far as possible before landing. This test resulted in a 4.9-fold decrease in the angle turned. We also tested the ability of three subjects to perform sharp running turns in a tight slalom course of six 90 degree turns. When the subjects ran with the 4.6-fold greater rotational inertia, the time to complete the course increased by 34 %. Hence, the results from these tests suggest that rotational inertia may have limited the turning performance of theropods. Characters such as retroverted pubes, reduced tail length, decreased body size, pneumatic vertebrae, and absence of teeth reduced rotational inertia in derived theropods and may have improved their turning agility. To reduce rotational inertia, theropods may have run with an arched back and tail, an S-curved neck, and forelimbs held backwards against the body.
P2.85 CARROLL, A.M.*, WAIN-WRGHT, P. C., University of California, Davis. Functional morphology of prey capture in the pallid sturgeon (Scaphirhynchus albus).
We examined the anatomical and kinematic basis of prey capture in sturgeon. Sturgeon (Acipenseridae) are a basal actinopterygians with a highly derived cranial morphology. Despite their anatomical singularity and phylogenetic significance, no functional study of the kinematics of sturgeon feeding has been published. Feeding pallid sturgeon (Scaphirhynchus albus) were filmed in lateral and ventral views at 250 frames per second. Feeding events were characterized by jaw opening, jaw protrusion, caudalventral retraction of the hyoid, ventral expansion of the branchial basket, and adduction followed by abduction of the opercular margin. Prey items were drawn into open jaws which were closed after prey entry, indicating that sturgeon feed by suction rather than biting. Evidence from muscle stimulation and anatomy support previously published hypotheses about the muscular basis of feeding kinematics. The sturgeon's jaws are not directly connected to its neurocranium, but are suspended from the hyoid arch and may be protruded ventrally. Protrusion is powered by the protractor hyomandibularis muscle which rotates the hyomandibula rostrally at its articulation to the neurocranium. This rostral rotation is transmitted to the jaws, which are deflected ventrally by the ventrally sloping underside of the neurocranium. This mechanism of jaw protrusion is unique to the order Acipenseriformes. The robust sternohyoideus drives hyoid retraction, jaw opening, and branchial basket expansion. Jaw opening by the sternohyoideus is the hypothesized ancestral jaw opening mechanism for actinopterygians. Despite the morphological differences between sturgeon and other lineages the kinematics of sturgeon feeding are essentially similar to other aquatic-feeding gnathostomes.
S9.12 CARRUTH, L.L.*, JONES, R.E., NORRIS, D.O., University of California at Los Angeles, University of Colorado, Boulder, University of Colorado, Boulder. Stress and Pacific salmon: a new look at the role of cortisol in olfaction and home-stream migration.
Pacific salmon (genus Oncorhynchus) exhibit an interesting and uncommon lifehistory-pattern that combines semelparity, anadromy, and navigation (homing). During smoltification, young salmon imprint on the chemical composition of their natal stream water (the home-stream olfactory bouquet or "HSOB"); they then migrate to the ocean where they spend a few years feeding prior to migrating back to their natal freshwater stream to spawn. Upstream migration is guided by the amazing ability to discriminate between the chemical compositions of different stream waters and thus identify and travel to their home-stream. Pacific salmon demonstrate marked somatic and neural degeneration changes during home-stream migration and at the spawning grounds. The appearance of these pathologies is correlated with a marked elevation in plasma cortisol levels. While the mechanisms of salmonid homing are not completely understood, it is known that adult salmon continuously utilize two of their primary sensory systems, olfaction and vision, during homing. Olfaction is the primary sensory system involved in freshwater homing and HSOB recognition, and will be emphasized here. I have hypothesized that the increase in plasma cortisol during home-stream migration of Pacific salmon is adaptive because it enhances the ability to recall the imprinted memory of the HSOB. Elevated plasma concentrations of cortisol could prime the hippocampus or other olfactory regions of the brain to recall this memory and, therefore, aid in directing the fish to their natal stream. Thus, specific responses of salmon to stressors could enhance reproductive success.
P3.9A CARSTENS, B. C.*, LUNDRIGAN, B. L.; Michigan State University Museum and the Departmen, Michigan State University Museum and the Departmen. A phylogeny of the American nectar-feeding bats (Chiroptera, Phyllostomidae) based on morphological characters.
There are forty-two recognized species of phyllostomid bats that feed primarily on nectar. As pollinators for more than three hundred species of plants the nectar-feeding members of the Phyllostomidae are an important component of neo-tropical ecosystems. We present a phylogeny of thirty-eight species of nectar-feeding bats based on 119 morphological characters. Our data support the Glossophaginae, Phyllonycterinae, and Brachyphyllinae as monophyletic clades, but suggest that nectar-feeding evolved multiple times within the Phyllostomidae. Examinations of skull morphology suggest that there are different adaptations that can facilitate the utilization of nectar as a resource in phyllostomid bats.
6.1 CARTER, T.L.*, ERICKSON, L.B., ELLIOTT, J. K., University of Puget Sound, Tacoma, WA. The influence of hybridization on anemonefish evolution.
Anemonefishes (Genera:Amphiprion and Premnas; Family Pomacentridae) are a group of 28 species of coral reef fishes that are obligate symbionts of large tropical sea anemones. A recent molecular phylogenetic study of anemonefishes, based on data from two mitochondrial genes (cyt b and 16S) for six representative species, produced a phylogeny that was significantly different from a previous phylogeny based on morphological data. To further evaluate this difference, we have sequenced another mitochondrial gene (ND2) and a nuclear gene (Tmo-4C4) for 14 species of anemonefishes. The phylogeny based on mitochondrial data was significantly different from the phylogeny based on nuclear data. Because mitchondrial DNA is maternally inherited, phylogenies based on mitochondrial data can be misleading if hybridization among species has occurred. At least one anemonefish species (Amphiprion leucokranos) is thought to be the result of hybridization between two very different anemonefish species (A. chrysopterus and A. sandaracinos). Both our mitochondrial and nuclear data provide molecular evidence for the hybrid origin of A. leucokranos. The nuclear data also indicate that other anemonefish species may be the result of past hybridization events. This suggests that hybridization may have been important in anemonefish speciation and that reticulate evolution is a plausible explanation for the diversification patterns observed in this group of coral reef fishes.
56.4 CASH, W.B.*, HOLBERTON, R.L., Maryville College, University of Maine, Orono. Stress and the slider turtle.
We examined physiological and behavioral questions related to stress, locomotor activity and dispersal movement in the slider turtle, Trachemys scripta. Like many other vertebrates, slider turtles show a corticosterone response to capture and handling, characterized by an increase in plasma corticosterone concentration with handling time. In the laboratory, turtles implanted with exogenous corticosterone showed a significant increase in caged locomotor activity when compared to control animals with empty implants. In the field, the effects of the simulated drying of a pond on the behavior of T. scripta were measured. Turtles responded to the draining of a pond by the emigration of the majority (75%) of the experimental population. Turtles had significantly elevated corticosterone when compared to individuals captured in a control pond, where conditions were held constant. However, 25% of the experimental group did not emigrate from the pond, suggesting that there is natural variation in turtle populations when responding to habitat declines, like rapidly decreasing quality or availability. Finally, aspects of the annual cycles of corticosterone were studied in wild and laboratory-held slider turtles. Male sliders were found to exhibit both a change in baseline corticosterone and the ability to respond to handling stress throughout the period studied. Female sliders did not show a significant difference in their baseline corticosterone concentrations, but did show a difference in their stress response over the sampling period. These results show collectively that corticosterone is involved with the ability of slider turtles to respond to environmental disturbances and corticosterone may ultimately be the proximate mechanism facilitating a stress avoidance response.
P2.90 CASOTTI, G., West Chester University. Microvilli within the lower intestine of sparrows.
Tissue from the lower intestine of two species of sparrow, the house sparrow Passer domesticus and savannah sparrow Passerculus sandwichensis was sectioned in an unbiased manner and examined quantitatively using stereology. The tissue was processed for light microscopy, and scanning and transmission electron microscopy to examine the extent to which microvilli enhanced the epithelial surface area of the rectum, coprodeum and cecae. Parameters measured included individual microvillus surface area, microvilli packing density and absolute surface area. In both species, a greater surface area and packing density of microvilli occurred within the rectum and the cecae. Overall, the three measured variables were not statistically significant between species at the 95% confidence level. In the cecae, microvilli within the savannah sparrow had a higher individual surface area, packing density and absolute surface area than in the house sparrow. The functional implications of a change in microvilli population are discussed in relation to retrograde peristalsis within the lower intestine of birds. Funded by a Pennsylvania State System of Higher Education Grant 2112-403.
P3.56 CASTO, J.M.*, PARKER-RENGA, I.M., KETTERSON, E.D., NOLAN, JR., V. Indiana University, Bloomington. Experimentally elevated testosterone in male dark-eyed juncos suppresses cell-mediated immune function of social mates and offspring.
The immunocompetence handicap hypothesis (ICHH) predicts that testosteronedependent secondary sexual signals that attract females also serve as honest indicators of male quality owing to testosterone's suppressive effect on immune function. Only males of high quality can express attractive traits and resist disease despite suppressed immunity. We have previously shown, as predicted by the ICHH, that experimental elevation of testosterone (T) in male darkeyed juncos suppresses immunity and enhances male attractiveness to females. We have also shown that T suppresses male parental behavior and that females attempt to compensate for reduced male care by increasing their own parental effort. Here we test whether the effects of treating males with T might extend beyond individual males and indirectly influence immune function of their social mates and offspring. We used wing-web swelling in response to an antigenic challenge as a test of cell-mediated immunity. We tested free-living females juncos that were mated to T-treated males (T-males) or controls (C-males), and tested offspring of those matings. We found that immune responses were significantly suppressed in mates of T-males (41% lower) and their offspring (19% lower) as compared to those of C-males. Combining these results with earlier findings, we suggest that the costs to males of T-induced attractiveness may go beyond immunosuppression. Reductions in T-nestling immunity may explain a previous finding that in juncos T-males fledge significantly fewer young from their nests than C-males. Additionally, the consequences for females of choosing males with traits enhanced by T appear to be more complicated than previously thought.
P1.69 CASTRILLO, L.A., LEE, R.E.* Jr., LEE, M., WAYMAN, J.A., Miami University, Oxford, OH, Miami University, Oxford. OH, Miami University, Oxford, OH, University of Wisconsin, Madison. Reduction of cold hardiness in overwintering Colorado potato beetles using ice nucleating bacteria.
A key factor in the overwintering survival of Colorado potato beetle (CPB) is the regulation of the temperature at which the insect freezes. Like most overwintering insects, CPBs are unable to survive internal ice formation. Winter survival is enhanced by both burrowing into the ground and by lowering their supercooling point, the temperature at which ice formation spontaneously occurs in their body fluids. We have shown that the supercooling capacity, a major factor in winter cold hardening of CPBs, can be regulated by exposure to ice nucleating active (INA) bacteria. Ingestion of INA Pseudomonas fluorescens immediately elevates the beetle's supercooling point. Furthermore, retention of the bacterium in burrowed CPBs' guts through winter increases their susceptibility to sub-zero temperatures. Reduction of the CPB's cold hardiness using INA bacteria offers a novel method for controlling these beetles by targeting the overwintering population.
3.2 CASTRO-SANTOS, T.*, HARO, A., University of Massachusetts, Amherst, S.O. Conte Anadromous Fish Research Center, U.S. G.
Optimal sprint speeds of fish traversing velocity barriers: further thoughts on burst-swimming data.
Migrating fish traversing velocity barriers are often forced to swim at speeds greater than Ucrit Since prolonged and burst-swimming are powered by inefficient anaerobic metabolic processes, models predicting optimal swim speeds based on maximized energetic efficiency are inappropriate in this situation. Instead of efficiency, fish need to maximize distance of ascent, both to maximize probability of success and to minimize the number of ascent attempts with their associated metabolic costs, recovery time, etc. From the standard fatigue-time equation (ln E = a + bU; E = endurance, U = swim speed), we show that there exists an optimal ground speed for maximizing traversed distance against any flow velocity greater than U crit and this speed equals –1/b. Six migratory fish species allowed to sprint volitionally against fixed flow velocities of 1.5 – 4.5 m*s–1 chose similar ground speeds regardless of flow velocity, supporting the hypothesis that sprinting speeds are modulated to maximize distance of ascent.
58.2 CAVEY, M.J.*, WILKENS, J.L., University of Calgary, Alberta, Canada. F-actin in the amuscular arteries of the American lobster.
Seven vessels leave the heart of the lobster Homarus americanus: the unpaired anterior median artery, sternal artery, and dorsal abdominal artery and the paired anterior lateral arteries and hepatic arteries. Superficially, these arteries have a common, relatively-simple organization, consisting of an elastic lamina next to the lumen, a multilayered endothelium, and an enveloping adventitia of collagen fibers. Patches of striated muscle cells occur in sectors of the dorsal abdominal artery. All of these arteries should serve as "capacitance" vessels, utilizing elastic elements to minimize the pulsatility of hemolymph flow from the heart. It has been proposed that lobster arteries, with the possible exception of the dorsal abdominal artery, cannot contribute to the differential distribution of hemolymph owing to the absence of diameter-regulating muscle (and, hence, the inability to control their individual resistances). Comparative ultrastructural studies have now revealed extensive networks of cytoplasmic filaments in the endothelial cells of the amuscular arteries. All vessels were prepared in tandem for immunohistochemistry for F-actin.They were slit lengthwise and opened onto microscope slides. The vascular spreads were fixed with formaldehyde, permeabilized with Triton-X 100, and stained with rhodamine phalloidin. Both sarcomeric myofilaments in the muscle cells of the dorsal abdominal artery and the aggregated filaments in the endothelial cells of the six amuscular arteries stain positively for F-actin. It thus appears that the muscular and amuscular arteries alike may have the properties of "resistance" vessels, possessing the contractile machinery by which to regulate their diameters and actively control hemolymph flow.
53.1 CAVIEDES-VIDAL, E., KARASOV,W.H.*, Universidad Nacional de San Luis, Argentina, University of Wisconsin, Madison. Developmental changes in digestive enzymes of nestling house sparrows, Passer domesticus.
Six decades of studies have speculated that digestive capacity might limit avian growth rate, or that developmental changes in the gut might determine developmental changes in digestive efficiency. However, there are no studies on digestive biochemistry during avian development, except for studies on mainly domestic birds that exhibit the precocial mode of development. We studied pancreatic and intestinal enzyme activities during development of a wild passerine bird exhibiting the altricial mode of development. Wild nestling house sparrows were studied immediately after removal from the nest (days 0, 3, 6 of age; day 0 = hatch), whereas captives were raised in the laboratory beginning day 3 on a formulated casein/starch-based diet until fledging age (after day 12). Digestive biochemistry was dynamic. Tissue-specific activities of some digestive enzymes continued to increase through fledging, by >10 times in some cases (e.g., sucrase and maltase in mid-intestine). Total pancreatic amylase activity increased 100 times between hatch and day 12 through a combination of increases in tissue specific activity and pancreas mass. House sparrows differ from poultry, in whom after about 2 weeks of age the specific activity of intestinal and pancreatic digestive enzymes is generally constant or declines during development. The data on intestinal and pancreatic enzymes help explain why digestive efficiency of nestling house sparrows improves with age, and the data seem consistent with the idea that digestive capacity might limit feeding rate and hence growth rate. Supported by grants from FONCYT to ECV, and NSF to WHK.
S12.6 CHAMBERLIN, M.E., Ohio University, Athens. Developmental changes in insect epithelial ion transport and metabolism.
Like other caterpillars, the tobacco hornworm (Manduca sexta) is essentially an eating machine that consumes large amounts of food to fuel the growth and development of the subsequent two developmental stages. Commensurate with its huge appetite is a large midgut, which is involved in the digestion and absorption of food as well as the transport of inorganic ions. The larval midgut, however, is destined to be destroyed and replaced by a pupal epithelium. Within the first two to three days of the fifth and final larval instar, there is a small increase hemolymph ecdysteroids. This small increase in ecdysteroids does not induce molting, but does commit the insect to metamorphosis. This commitment is manifested on day 5 of the instar (wandering stage), as indicated by the appearance of a dorsal vessel and cessation of feeding. At the same time midgut short-circuit current and transepithelial potential decline 80% and 49%, respectively. Mitochondrial metabolism is also altered upon the onset of wandering. Mitochondria isolated from the midguts of day 5 larvae oxidize palmitoyl carnitine and succinate at rates that are 40% and 60% of the respective rates in mitochondria isolated from day 4 larvae. In addition, the membrane potential is lower in mitochondria isolated from the midguts of wandering larvae. Because these physiological and metabolic changes coincide with the onset of wandering, the midgut appears to modulated by ecdysteroids. Furthermore, the changes in midgut metabolism and ion transport occur abruptly, indicating that the larval midgut is destroyed by programmed cell death, rather than by a gradual senescence of the tissue.
70.2 CHAN, S.- M., GU, P.-L., University of Hong Kong. The study of shrimp CHH/MIH/GIH gene family: gene structure, expression and biological assay of recombinant neuropeptides.
The crustacean CHH/MIH/GIH neuropeptide family constitutes a group of important hormone that regulates important processes such as molting, glucose metabolism and reproduction. The characterization of these neuropeptides has attracted much attention due to their potential importance in aquaculture. By RT-PCR and library screening approach, we have isolated and cloned four cDNAs from the eyestalk of the shrimp Metapenaeus ensis. Two of the cDNAs encoded for proteins are homologous to the CHH-subtypes and two of the cDNA encoded for proteins belong to the MIH/GIH subtypes. The organizations of these genes are very similar. They consist of three exons and two introns with conserved location of boundaries between the intronexon. There are more than 20 CHH-A genes, 5-6 CHH-B genes and 1-2 copies of MIH and GIH gene in the shrimp genome. CHH-A, CHH-B, MIH- and GIH RNA transcripts can be detected in the eyestalk of animal at most stages. Only CHH-A and GIH transcripts are detected in ventral nerve cord. Recombinant proteins for these neuropeptides have been produced and used for bioassay. Additionally, the recombinant proteins were purified for antibody generation. Specific antibodies against these recombinant proteins were generated and had been used to detect these neuropeptides by immunochemistry. Supported in part by a HKU institutional grant (CRCG) and the RGC of the HKSAR, China (HKU 7229/00M)
P3.84 CHAN, S.- M., GU, P.-L., University of Hong Kong. Molecular characterization of a cDNA encoding for a shrimp cellular retinoic acid/retinol binding protein.
Members of the cellular retinoic acid binding-protein (CRABP) family are small proteins involved in the metabolic pathways of retinoic acid (RA). Although there is report describing the cloning of a retinoic-X receptor, no report describes the presence of RA in crustacean. To determine whether RA is also involved in the regulation of development and whether CRABP is also involved in the metabolism of RA in crustacean, we attempt to clone the CRABP cDNAs from the shrimp using a combination of RT-PCR and library screening approach. Several identical cDNA clones encoding the putative MeCRABP were isolated. As confirmed by DNA sequence determination and RNA Northern blot analysis, the size of the CRABP mRNA is 0.9 kb. The cDNA is estimated to encode for a protein of 14 kDa. The size is close to that of the retinoic/fatty acid binding protein reported in the vertebrate and invertebrate. MeCRABP is expressed abundantly in the ovary and moderately in the eyestalk. Other tissues such as the muscles and testis also express these genes. Recombinant protein for the shrimp CRABP was produced in a pRSET bacteria expression system. Purified fusion protein was used to immunize rabbit to raise antibody. The fusion protein binds to both retinoic acid (RA) and retinol (RO) with similar affinity. Anti-rCRABP recognises cells of the eyestalk as well as maturing oocytes of shrimp contain CRABP. Supported by HKU CRCG.
S4.4 CHANG, E.S., Bodega Marine Laboratory, University of California. Hormones in the lives of crustaceans: an overview.
Decapod crustaceans have been a particularly interesting and rewarding group of animals for the study of comparative endocrinology. Most of the published studies, however, have dealt with the hormones of the adult stage; relatively few studies have addressed the hormones of the embryonic and larval stages. The most widely studied hormones during crustacean ontogeny are the arthropod molting hormones—the ecdysteroids. Following a brief survey of crustacean endocrinology, I will present a selected review of what is known about ecdysteroids in the various crustacean life stages. The ecdysteroids are multifunctional and are involved in a number of life processes (growth, regeneration, and reproduction). I will also discuss aspects of the terpenoid hormone methyl farnesoate and the crustacean hyperglycemic hormone neuropeptide family during ontogeny.
P1.98 CHANG, M.H*, CHEDIACK, J.G., CAVIEDES-VIDAL, E., KARASOV, W.H., University of Wisconsin, Madison, University Nacional de San Luis, Argentina, University Nacional de San Luis, Argentina, University of Wisconsin, Madison. Enhanced passive absorption in the presence of luminal nutrients in house sparrows.
We previously demonstrated in house sparrows substantial absorption in vivo of L-glucose, the stereoisomer of D-glucose that does not interact with the intestine's D-glucose transporter. The mechanism, as first proposed by Pappenheimer and coworkers in 1987, might be solvent drag through paracellular spaces, activated by Na+– coupled nutrient transport. This hypothesis predicts that absorption of L-glucose might be highest when it is administered orally in the presence of D-glucose and/or amino acids. We tested this in two experiments with house sparrows (Passer domesticus) using pharmacokinetic methods to measure absorption. In Exp. 1, fractional absorption of L-glucose (administered by oral gavage and measured by enzymatic method in plasma) in fed sparrows was higher (0.46 +– 0.02, n = 7) than in sparrows fasted 12 h (0.40 +– 0.01, n = 6) (simple t-test T = –2.27, P = 0.044, DF= 11). The greater absorption was apparently not due simply to longer retention time of digesta, because no significant difference was found for retention times. In Exp. 2, fractional absorption of radiolabeled L-glucose was significantly higher when administered to fasted birds in solution with 200 mM D-glucose (+ 80 mM NaCl) than when administered with 200 mM mannitol (+ 80 mM NaCl) (respectively, 0.79 + 0.04 vs. 0.66 + 0.03; T= –2.47, P=0.035, DF= 9). In the former group, the absorption rate of L-glucose, determined by pharmacokinetic methods, was 67% faster (P = 0.032). Our results are consistent with the solvent-drag hypothesis, and indicate that small, hydrophilic compounds are absorbed faster and to a greater extent when there are nutrients (e.g., sugar, amino acids) in the gut. Supported by FONCYT (01-03101) to ECV, and NSF IBN-9723793 to WHK.
P2.13 CHARLESWORTH, T.D., LEHMAN, A.H.*, BLACKBURN, D. G., Trinity College, Hartford. Cytology and ultrastructure of the extraembryonic membranes of the quail, Coturnix coturnix.
In avian eggs, the yolk sac and chorioallantoic membrane (CAM) provide nutrients and gas exchange for the developing embryo. Despite avian diversity, most of what is known about anatomy and physiology of these extraembryonic membranes in birds comes from studies on the domestic chicken. Quail tissues were harvested at Days 7 and 14 following oviposition, and studied by means of transmission EM and light microscopy of resin-embedded tissues. Chick tissues were sampled for comparison. At Day 7, the yolk sac is trilaminar, consisting of a thin monolayer of squamous epithelial cells, the vitelline capillaries, and the underlying yolk endoderm. The endodermal cells are rich in mitochondria and phagocytosed yolk droplets. Between the first and second week of incubation, the CAM undergoes progressive expansion at the expense of the yolk sac, and lines much of the inner surface of the eggshell with allantoic vessels. A thin squamous epithelium overlies the allantoic capillaries, providing a thin barrier to respiratory exchange. Tall intercalated cells with microvilli and abundant mitochondria span the CAM, extending towards the shell membrane. These cells have been implicated in calcium uptake in the chick by previous workers. Given that qualitative cytological differences between the quail and chick were not observed, our ongoing work is focusing on quantitative comparisons in abundance and ontogeny of cell populations.
S4.3 CHARMANTIER, G., University of Montpellier, France. Ontogeny of osmoregulation in crustaceans : the embryonic phase.
Three patterns of ontogeny of postembryonic osmoregulation have been recognized in crustaceans : (1) osmoregulation varies little with development stage and the adults are weak regulators or osmoconformers; (2) the adult type of efficient osmoregulation is established in the first postembryonic stage; (3) metamorphosis marks the appearance of the adult type of osmoregulation, generallyalong with the occurrence of ion-transporting cells and Na-K ATPase in diverse organs. This review will concentrate on the ontogeny of osmoregulation in embryos, particularly in species belonging to type 2 : they are euryhaline and so are their hatchlings. Embryos are osmotically protected against variations in environmental salinity levels, either by closed incubating pouches (in some cladocerans and isopods), semi-closed pouches (where osmolality is at least partially controlled by the diverted female urine, in some amphipods), or more generally by egg membranes (in species whose eggs are directly exposed to the ambient medium). In some species, temporary (e.g. dorsal organs in amphipods) or definitive (e.g. gills in crayfish) osmoregulatory organs, where ionocytes are located, develop in embryos and the activity of Na-K ATPase increases concomitantly. The ability to osmoregulate is thus acquired during the embryonic development, resulting in osmoregulating hatchlings, which is a necessary and key adaptation for species spending their entire life-cycle at low (particularly in fresh water), high or variable salinity.
S4 CHARMANTIER, G. *, WOLCOTT, D. L., University of Montpellier, France, University of North Carolina, Raleigh. Ontogenetic strategies of invertebrates in aquatic environments: introductory note.
Aquatic organisms are subjected to multiple environmental factors wielding a selection pressure upon them. As natural selection acts on all developmental stages, the successful establishment of a species in a given habitat depends on the ability of each of its developmental stages to accommodate these external conditions and their variations. Species may show congruence in behavioral and physiological strategies that are constrained by the rigors of the aquatic environment, especially during development. The evolutionary consequences are important, and have generated increasing interest. The symposium, which brings together physiologists and ecologists, aims at a better understanding of ontogenetic strategies in aquatic environments, and their evolutionary significance. The symposium will successively focus, largely in crustaceans, on the ontogeny of gas exchange (N.B. Terwilliger), cardiac function (J.I. Spicer), osmoregulation (G. Charmantier), the appearance of hormonal coordinations (E.S. Chang), on vision (T.W. Cronin), on induction of quiescence and diapause (S.C. Hand), and on transition to non-marine conditions (K. Anger). Behavioral and ecological aspects of transport, settlement (R.B. Forward, C.M. Young), and metamorphic competence (M.J. Hadfield) in several invertebrate phyla will also be addressed. D.L. Wolcott will act as panel moderator.
13.2 CHEEK, A.O.*, BROUWER, T.H., CARROLL, S., MANNING, S., MCLACHLAN, J.A., BROUWER, M., Southeastern Louisiana University, Hammond, University Southern Mississippi, Ocean Springs, University Southern Mississippi, Ocean Springs, University Southern Mississippi, Ocean Springs, Tulane University, New Orleans, LA, University Southern Mississippi. Experimental evaluation of vitellogenin as a predictive biomarker for reproductive disruption.
Vitellogenin (VTG) synthesis in male oviparous vertebrates is used as an indicator of environmental estrogen exposure, yet the reproductive consequences of exposure are unknown. To examine whether VTG expression predicts reproductive impairment, we exposed medaka fry (Oryzias latipes) for 2 or 8 weeks post-hatch to 0, 0.5, 1.0, 2.5, and 7.5 ppb of the environmental estrogen o, p' DDT. Fish were sampled 2, 4, and 8 weeks after hatch to examine gonad histology and VTG expression. After exposure, fish were transferred to clean water, grown to sexual maturity, and placed in mating pairs. Eggs were collected for 7 days and scored for fecundity, fertility, and hatching success. Two week exposure had no effect on VTG expression, while all doses induced VTG after 8 weeks. The highest doses of DDT caused a female-skewed sex ratio in adults. Gonadal feminization appeared to be progressive - some ovotestes appeared after 2 and 4 weeks exposure to the two highest doses, but the proportion of ovaries increased after 8 weeks. Both two and eight week exposure significantly reduced fertility and hatching success at all doses, but lower doses had a greater effect after longer exposure. Fertility and hatching success were more sensitive to estrogenic disruption than was VTG synthesis. Therefore, VTG expression may be interpreted as a warning of reproductive consequences, but absence of expression cannot be interpreted as absence of developmental and reproductive disruption.
P3.41 CHENG, C.-H.C., University of Illinois, Urbana. Antifreeze glycoprotein genes in temperate water notothenioid fish infer an Antarctic origin of speciation.
The perciform suborder of otothenioid fishes is indigenous to the Southern Ocean and largely endemic to the Antarctic region. Currently 8 families encompassing 130 species are recognized. Twelve species makes up 3 basal, non-Antarctic families inhabiting the temperate regions of S. America, Australia, and New Zealand. The majority of the species make up the other 5 families, most of which are confined to the Antarctic region; only about 14 species of these have a sub-Antarctic and south temperate distribution. The Antarctic water is isolated from other southern oceans by the Antarctic Circumpolar Current (ACC), a major oceanographic barrier which also prevents dispersal of fish in either direction. The 3 basal families presumably diverged and became along the south temperate continents before Antarctica was fully isolated (22–25mya). The 5 endemic Antarctic families are thought to have arisen in situ within the Antarctic water, the result of an adaptive radiation underwent by the ancestral notothenioid stock which evolved antifreeze glycoproteins (AFGP) to avoid freezing as the Antarctic water chilled to subzero temperatures. Given the ACC barrier to dispersal, the origin of the extant south temperate notothenioids has been an enigma. Since AFGP gene evolved once before the notothenioid radiation, and its evolution was directly linked to the freezing of the Antarctic water, the presence of AFGP genes in the extant temperate water notothenioids can be used as a marker to infer their geographic origin of speciation. Several species were found to have AFGP genes, two even express the protein at low levels, which would argue for an Antarctic origin of speciation where and when antifreeze protection was needed, and a subsequent escape to the south temperate regions.
8.5 CHIU, C.-H. P.*, WAGNER, G. P.*, Yale University. Molecular evolution across the finlimb transition.
Evolutionary innovations in morphological characters are realized through the evolutionary modification of genes controlling the development of the characters. We follow this line of thought and examine the evolution of genes involved in the development of fins and limbs to gain insights into the molecular underpinnings of the origin of tetrapod limbs. Specifically we study the coding and non-coding regions of Hoxa-11 and Hoxa-13.The coding region of Hoxa-11 does not show a burst of substitutions in most of its coding region during the fin-limb transition. There is, however, an association between the presence of a cluster of Alanine residues in the Hoxa-11 protein and the derived expression pattern of Hoxa-11 typical for eutetrapods. In the non coding region we find several conserved sequences. One protein binding sequence is found in the intron and is conserved between zebra-fish, coelacanth and tetrapods. Another one is found in the 5í non-coding region and shows a clade specific pattern of sequence conservation and protein binding. This result suggests that it may represent a tetrapod specific enhancer element. The coding region of Hoxa-13 also shows a tendency to acquire Alanine repeats, but in contrast to Hoxa-11 this event is not associated with the fin-limb transition but with the origin of the mammals. We conclude that the comparison of sequences among fish and tetrapods reveals several candidate differences that may be involved in major developmental transformations during the evolution of vertebrates.
36.3 CHRISTIANS, J.K., WILLIAMS, T.D. *, Simon Fraser University, Burnaby, BC. Effects of porcine follicle-stimulating hormone on the reproductive performance of female zebra finches (Taeniopygia guttata).
It has been suggested that follicle-stimulating hormone (FSH) may play a role in egg size/number trade-offs in oviparous vertebrates. We tested this hypothesis in an avian species by administering porcine FSH (pFSH) to intact, captive female zebra finches (Taeniopygia guttata) during egg formation. We predicted that 1) low doses of pFSH would increase yolk deposition and so increase egg mass; 2) higher doses of pFSH would increase the number of ovarian follicles recruited into rapid yolk development, and so increase clutch size; and 3) an increase in clutch size at high doses would lead to a reduction in egg size. Although a range of pFSH doses decreased egg mass by ca. 10% in three separate experiments, the reduction in egg mass occurred in the absence of an increase in clutch size. Porcine FSH actually reduced the number of eggs laid, although only the difference in median clutch size (and not mean clutch size) was statistically significant in two experiments. The results of this study did not support the hypothesis that FSH mediates a trade-off between egg size and clutch size in birds.
P1.58 CHRISTMAN, T.M.*, FINKLER, M.S., Indiana University Kokomo. Overwintering energetics of the red-backed salamander, Plethodon cinereus.
Red-backed salamanders are known to actively forage during the winter. The present study examined the importance of successful foraging to the overall energy budget during overwintering. We measured oxygen consumption rate and whole-body triglyceride and glycogen contents before and after a five-month overwintering period in salamanders that were either unfed or fed 5 fruit flies 3x per week. Oxygen consumption increased markedly over the course of overwintering, with a nearly two-fold increase in fed animals. Unfed animals initially had greater rates of oxygen consumption than did fed animals, but this difference disappeared by the end of overwintering. The triglyceride and glycogen contents of fed animals at the end of overwintering did not differ from those at the beginning of overwintering, whereas both values decreased significantly in unfed animals. Though preliminary, the data suggest that winter foraging may be an important component of the energy budgets of P. cinereus. Moreover, the data highlight changes in metabolic rate during the course of overwintering that may need consideration in estimates of overwintering energy budgets.
P3.50 CHUNFA, W., PATINO, R.*, DAVIS, K.B., Texas Tech University, Texas Tech University, University of Memphis. Cellular distribution of estrogen receptor alpha and beta transcripts in the testis of channel catfish.
The cellular distributions of estrogen receptor ALPHA (ER-ALPHA) and ER-BETA in the testis have not been determined and compared in non-mammalian vertebrates. In this study, we examined the cellular distributions of ER-ALPHA and ER-BETA RNA in the testis of adult and juvenile channel catfish by in-situ hybridization.The cRNA probes used contained 5'-terminal end sequence that is specific for each receptor subtype. Tubules in the anterior region of the catfish testis contain the germinal elements, and in the adult fish examined the tubules were spermatogenic and had free sperm. Hybridization signal strength (antisense probe) for both receptor subtypes was low in primary spermatocytes and increased in secondary spermatocytes and spermatids. The most abundant signals for ER-ALPHA and ER-BETA RNA were observed in sperm. The presence of ER transcript in spermatogonia could not be determined since it was difficult to identify these cells in the hybridized tissue sections. Tubules in the posterior region of the catfish testis contain non-germinal columnar epithelium, and weak signals for ER-ALPHA and ER-BETA RNA were detected in the vicinity of the apical nuclei. The testes of the juvenile (pre-spermatogenic) catfish examined also showed signals for ER-ALPHA and ER-BETA RNA, preferentially in the stroma. In conclusion, ER-ALPHA and ER-BETA genes are both transcribed in the catfish testis and in the same cell types.Their transcripts are found preferentially in the germ cells of adult males and in the testicular stroma of juvenile males. Of particular interest is the high level of ER RNA content in sperm. These observations suggest that estrogens play important roles in the regulation of testicular physiology and spermatogenesis in channel catfish.
P1.25 CIURA, S. M., BIBEAU, M.R., SCHULTE, P.M.*, University of Waterloo, Ontario. Intraspecific variation in heat shock proteins and thermal tolerance.
Populations of Fundulus heteroclitus are distributed through a thermal cline along the Atlantic Coast of North America, from Newfoundland to Florida. At the northern end of the species range, fish experience average annual temperatures 12 degrees cooler than their southern counterparts. To determine the maximum critical temperature (CTmax) of fish from the northern and southern populations, fish were acclimated to common conditions of 20 degrees celcius in the laboratory. These fish were exposed to increasing water temperature at a rate of 0.3 degrees per minute until they were unable to maintain their orientation. CTmax was significantly higher in the southern population (p<0.01). To address the molecular basis of this difference, we have cloned and sequenced the 70 kD heat shock protein and heat shock cognate from both populations. There are several amino acid differences between the two genotypes, which could be functionally important. We have also examined circadian variation in thermal tolerance. In fish held at short-day photoperiod, but at constant temperature, there is a diurnal rhythm in CTmax, with thermal tolerance at noon being significantly higher than early morning and evening values. In contrast, fish held at a long-day photoperiod do not exhibit this diurnal rhythm. Values of CTmax for these fish are uniformly high. The diurnal rhythm at short-day photoperiod could represent a strategy for coping with daily variation in temperature during the spring and fall in the natural habitat.
33.2 CLAIBORNE, J. B.*, GUNNING, D. L., WALL, B. P., MORRISON-SHETLAR, A.I., Georgia Southern University, Statesboro. Gill Na+/H+ antiporters (NHE) in marine fish.
The branchial epithelium in marine fish is the main site of acid-base transfers between the extracellular space and the environment. Na+/H+ exchange proteins (NHE) are thought to contribute to net acid excretion in these animals. We have used molecular and biochemical methods to detect these antiporters in the branchial epithelium of two species of fish. 3'/5'-RACE reactions allowed us to clone and sequence for the first time a full length cDNA transcript for an NHE-2-like isoform from the gills of the marine long-horned sculpin (Myoxocephalus octodecimspinosus). The open reading frame is approximately 2890 bp in length and has a 57% amino acid homology to the rat NHE-2 isoform with much lower homology at the 3' end. We have previously shown NHE-1 like immunoreactivity in the gills of the sculpin and the seawater adapted mummichog (Fundulus heteroclitus). Using Western analysis on gill membrane preparations from fresh and seawater adapted mummichogs, we have now observed proteins approximately 80 kDa and 77 kDa in size that are immunoreactive to antibodies made against mammalian NHE-1 (aa 514-818) and NHE-3 (aa 528-648), respectively. Following exposure of this species to 1% hypercapnia for one hour, an increase in expression was detected for both NHE-like protein isoforms in seawater adapted animals, while no difference in expression of NHE-1-like proteins could be detected in freshwater adapted fish. We hypothesize that during acidosis, apical gill NHE activity enhances net H+ transfers to the water in these marine species. Supported by NSF-IBN-9808141 to JBC and AIMS.
S12.4 CLARK, T.M., Indiana University South Bend. Integrative aspects of epithelial transport in larval Aedes aegypti.
In contrast to the extensively studied hormonal regulation of Malpighian tubule function, regulation of midgut transport has been largely ignored. 5-hydroxytryptamine (5-HT; serotonin) is perhaps best known among insect transport physiologists as one of a suite of hormones regulating Malpighian tubule function. In larval Aedes aegypti, Malpighian tubule secretion rates are stimulated by increasing hemolymph 5-HT concentrations as ambient salinity increases. First principles dictate that larvae must coordinate changes in Malpighian tubule secretion rates with selective recovery of water and ions in other regions of the excretory system to remain in homeostasis as ambient salinity changes. Recent evidence suggests that the midgut is involved in this coordinated regulation of hemolymph composition. 5-HT at concentrations known to exist in hemolymph and to stimulate Malpighian tubule transport hyperpolarizes the transepithelial potential of both the anterior and the posterior stomach regions. 5-HT regulates different mechanisms in the two regions. The actions of 5-HT in anterior stomach are confined to the basal membrane of a subset of cells. The physiological significance of stimulation of midgut and Malpighian tubule function by a single hormone is not yet understood. However, stimulation by 5-HT of both midgut and Malpighian tubule transport provides support for a model in which the actions of multiple systems are coordinated by a single hormone to regulate hemolymph composition. Furthermore, stimulation by 5-HT of midgut and Malpighian tubule transport in response to saline loads in exopterygotes (Rhodnius), and endopterygotes (Aedes), suggests that its primary function as a regulator of hemolymph composition through coordinated actions on organ systems traditionally considered separately may be very highly conserved among insects.
P1.81 CLARK, T.M.*, HUTCHINSON, M.J., MOFFETT, D. F., Indiana Univ, South Bend, Washington State Univ, Pullman, State Univ, Pullman. Apical surface morphology of the stomach region of the larval mosquito midgut.
Mature 4th instar larval Aedes aegypti measuring 6.5±0.19 mm in length have a stomach region of 3.3±0.18 mm (N=6). The stomach is clearly differentiated into distinct anterior, transitional and posterior regions (53.0±1.16%, 13.7±1.16%, and 33.3±0% of total stomach length respectively). The anterior stomach consists of cells that range from 5.7 to 44.4 mm in diameter (mean 28.6±1.68 mm). These cells are uniform in appearance and show a normal distribution by diameter. They have polygonal, flat apical surfaces with very short microvilli (0.4±0.02 mm). There are no intercellular clefts apparent at the level of SEM, rather the surface of the epithelium is smooth.The most anterior cells of the transitional region are similar in appearance to cells of the preceding anterior stomach region but have microvilli 1.2±0.03 mm in length. Microvillar length increases to 2.3±0.26 mm in the mid-transitional region, and to 4.2±0.25 mm in the posterior transitional region. The mean diameter of transitional region cells is 21.0±1.26 mm.The transitional region cells show a progression to a more rounded apical profile from anterior to posterior. Posterior stomach cells are characterized by globular protrusions of the apical surface that are separated by relatively deep clefts containing numerous microvilli, that were not observed in other stomach regions. Posterior stomach cell diameter is uniformly 19.7±1.08 mm throughout the anterior 2/3 of the posterior stomach (N=22) and increases to 26.2±1.45 mm (N = 8) in the posterior third of the posterior stomach region (P<0.0005).
59.2 CLIFFORD, A.B.*, WITMER, L.M., Ohio University, Athens, Ohio University College of Osteopathic Medicine. The narial anatomy of hooded seals (Cystophora cristata) with respect to other Carnivora.
Male hooded seals (Phocidae: Cystophora cristata) have two inflatable devices, both of which involve modification of their narial and facial anatomy. 1) An inflatable integumentary bladder is formed as the elastic and hairy epithelium covering the narial region is inflated following closure of both nostrils. 2) The "red bladder" is formed as a highly elastic portion of the nasal septal mucosa is extruded out one nostril with the contralateral nostril shut. Both devices are used as visual displays, the first year round and the second during the mating season. The unique narial anatomy of adult male hooded seals was studied via CT scanning, dissection, and skeletonization of fresh heads. Comparisons involved similar studies of adult female and juvenile hooded seals, and adults of bearded seals, black bear, and coyote; skulls of other phocid and otariid species were examined. Among the anatomical specializations associated with this functional complex are expansion of the nasal vestibule, retraction of the bony naris, increased elasticity in the narial skin and membranous nasal septum, transformation of the nasal cartilages, elaboration of certain facial muscles that are inconspicuous in outgroups, and changes in numerous bony features. Adult female and juvenile hooded seals are skeletally more like adult males but the associated soft tissues are less developed. Oddly, the mechanism of nostril closure remains enigmatic. The functional anatomy of the hood is important in that it is the nominative attribute of the species; moreover, it has bearing on the general evolution of probosces in mammals and even on inferences of similar inflatable narial structures in extinct taxa such as hadrosaurian dinosaurs.
S2.2 COATES, M.I., University College London. Fins to limbs: what the fossils say.
The fin to limb transition is one of the pivotal morphological transformations in vertebrate history. Fossil outgroups of tetrapods bear fins with a simple iterative pattern oriented proximo-distally; several features of these fins are also present in extant lungfish. Certain examples of fossil fins long considered close to tetrapod limbs, have now been removed to more remote phylogenetic positions. Their apparent similarities thus appear convergent. The most derived ëfishí (i.e. pre-limbed) members of the tetrapod stem-lineage (panderichthyids) show modest enlargement of the fin-girdles. This coincides with reduction of endoskeletal outgrowth, the presence of an expanded plate adjacent to the probable homologue of the intermedium, and changes in the proportions of proximal fin radials to more closely resemble the humerus, radius and ulna of primitive, digited, limbs. The earliest limbs date from the uppermost Devonian (360 mya). Of these, the forelimb of Acanthostega is arguably the most primitive. Like other Devonian examples it is polydactylous, but, uniquely, the wrist includes only a single, cylindrical, bone, quite unlike cross-articulating wrist and ankle structures of more recent limbs. All known primitive hindlimbs include a well ossified ankle, but in the earliest examples this includes fewer and larger elements than in more recent, derived, limbs. Functionally, these simple ankles are consistent with a likely paddle-like function. The most recent phylogenetic analyses indicate that pentadactyly evolved once, at a node within the tetrapod stem-lineage preceding the divergence of amniotes and lissamphibians. By this point in tetrapod phylogeny, it is also noticeable that markers of muscle insertion areas have moved proximally, corresponding to greater development of the endoskeletal girdles.
18.2 COATES, M.M.*, THOMPSON, S. H., Stanford University. Vision in a cubozoan jellyfish.
Jellyfish of the class Cubozoa possess camera-type eyes similar to those of cephalopods and vertebrates; consisting of a lens, cornea, and retina. The retina is composed of three layers: a sensory layer, a pigmented layer, and a nuclear layer with extending nerve fibers. The cells of the retina are all ciliated primary photoreceptors. These complex eyes are located on sensory clubs called rhopalia. Each animal has four rhopalia, and each rhopalium has two camera-type eyes as well as four simple ocelli. In spite of all this visual hardware, little is known of the visual capabilities of these animals and specifically the function of the remarkable complex eyes. We want to determine what information these eyes extract from the environmentand how the nervous system processes that information. We are studying these questions using behavioral and electrophysiological approaches. At Hopkins Marine Station, we have established a colony of Tripedalia cystophora, a small cubozoan from Puerto Rico. These cubomedusae exhibit strong attraction to light. Taking advantage of this behavior, we measured the spectral sensitivity curve of the eye and performed wavelength discrimination experiments. We then used extracellular recording methods to measure the electroretinogram (ERG) of the complex eye in response to flashes of different wavelengths and durations. This allowed us to compare the spectral sensitivity of behavioral responses to the retinal spectral sensitivity and to learn response time characteristics. This will help elucidate the type and quality of visual information available to this cubozoan. Funding: NSF and Myers Grant to M.C.; NSF to S.T.
S1.4 COCROFT, R. B., University of Missouri, Columbia. Vibrational communication and the ecology of group-living insects.
I will review the role of vibrational communication in group-living, herbivorous insects (not including eusocial insects). Social behavior in these taxa includes parental care of aggregated offspring, as well as grouping among cohorts of immatures or adults. I focus on the ways in which the ecological context favors cooperation or competition within groups, and how these outcomes are mediated by communication among group members. I will highlight studies of two membracid treehoppers with different life histories, in which siblings communicate in relation to important features of the environment. In both species, signaling interactions contain a large element of cooperation. I also survey examples of communication in other group-living herbivorous insects, exploring the possibilities of convergence in signaling systems that function in similar ecological contexts.
62.4 COLLIN, R.*, CHAPARRO, O. R., University of Chicago and The Field Museum, Universidad Austral, Chile. Loss of feeding larvae in Crepidula (Gastropoda: Calyptraeidae) is not irreversible.
It is thought that species of marine invertebrates with planktotrophic development commonly give rise to species with direct development. Direct developers often lose the complex morphological characters necessary for planktotrophic development and therefore cannot give rise to species with planktotrophic larvae. Here we show that, contrary to expectation, planktotrophic development in Crepidula fecunda appears to be derived from a direct developing ancestor, C. dilatata. Phylogenetic analysis of 640 basepairs of cytochrome oxidase subunit I mtDNA show that C. fecunda nests within a paraphyletic C. dilatata and that the three successive sister groups are all species with direct development. The direct developing embryos of C. dilatata retain a velum with a functional oposed band ciliary mechanism and a complete gut. These morphological and phylogenetic data both support the scenario in which the planktotrophic C. fecunda arose from the direct developing C. dilatata.
23.5 COMBES, S. A.*, TRIMBLE, A.C., DANIEL, T.L., University of Washington, Seattle. Spatial profiles of wing stiffness in hawkmoths and dragonflies.
Insect flight performance depends strongly on the dynamic geometry of wings. The curvature of the trailing edge, in particular, is a crucial determinant of aerodynamic force generation. In insects, wing curvature results from the instantaneous interaction between aerodynamic forces and bending stiffness. If bending stiffness varies spatially, then regional flow control is possible, suggesting a passive mechanism of stability. To examine this structural heterogeneity and its consequences for flight aerodynamics, we characterize spatial variation of wing flexural stiffness in both the spanwise and chordwise direction of insect wings. We measure the surface shape of wings by multiple laser ranging techniques, and then calculate flexural stiffness along the wing by comparing the surface shape of wings before and after loading the tip with a known force. We compare the spatial distribution of wing stiffness in the hawkmoth, Manduca sexta, and an aeshnid dragonfly, Aeshna multicolor. These insects, both excellent fliers, differ greatly in wing shape and venation pattern. Despite such morphological differences, we find that the profile of flexural stiffness in the spanwise direction is remarkably similar in both species, with a peak in stiffness located between 1/3 and 1/2 of wing span, and a sharp drop in stiffness (2 fold) past this point. In contrast, chordwise stiffness differs in the two species; in Manduca, stiffness falls sharply towards the trailing edge, while the dragonfly does not display this abrupt drop. Thus, trailing edge curvature and chordwise flow may differ significantly in these species.
9.3 COOKE SCHREIBER, S. M.*, JURY, S., WATSON, W.H., University of New Hampshire, Carribean Marine Research Center, University of New Hampshire. Seasonal differences in behavioral thermoregulation in the lobster, Homarus americanus.
Lobsters in the Great Bay estuary (NH) undergo a seasonal migration, possibly cued by changes in water temperature. Previous work on their thermal preference indicated that lobsters gravitate toward a final thermal preferendum slightly above normal summer conditions (Crossin et al., 1998). We conducted avoidance studies, during which lobsters were exposed to increasing temperatures (rate of change < 0.2fC/min) until they left their shelters. "Summer-acclimated" lobsters (15fC) exhibited avoidance responses when the temperature reached 22fC, well above their preferred range of 15–18fC. However, winter lobsters (ambient = 4fC) exhibited avoidance behaviors at 13.5fC, before the temperature reached their preferred levels. This suggests that avoidance behaviors are initiated by a relative increase in temperature (+7–9fC) rather than by exposure to an absolute temperature. Heart and ventilation rates also showed a linear increase in rate over most of the range of observed estuarine temperatures (Q10 = 1.8, 5–20fC). Thus, an increase of 7–9fC would approximately double their metabolism. Our working hypothesis is that, during these fairly rapid thermal increases, lobster movements are triggered by changes in metabolic rate, rather than sensory inputs indicating a rise in temperature or an absolute temperature. This study was supported by NOAA (SeaGrant) and the USDA (Hatch).
P3.83 COOMBS, S.*, ANDERSON, E.J., BRAUN, C. B., GROSENBAUGH, M.A., Loyola University Chicago, Woods Hole Ocean. Inst. How fish body parts alter local hydrodynamic stimuli to the lateral line.
Mottled sculpin (Cottus bairdi), like many fish, use their lateral line system to form hydrodynamic images of the environment. Although these small (10 cm long), benthic fish inhabit streams and lakes with significant ambient water motion, information about lateral linefunction comes largely from still-water conditions. We used digital particle image velocimetry to determine how uniform flow fields (2–8 cm/s) near the sculpin were altered along a horizontal plane at the level of the trunk lateral line canal. In the absence of the fish and at distances > 2 cm away from the fish, the mean direction and magnitude of the flow field was spatially homogenous at all flow speeds. Small scale (< 5 cm), ambient turbulence was negligible at 2 cm/s, but increasingly more pronounced at higher flow speeds. Flow around the fish's head, pointed upstream, was typical for that around a rigid body and could be predicted by a potential flow model. Flow around the large, extended pectoral fin, pointed downstream, showed separation at the edge of the fin and a trailing wake, similar to that observed for a flat plate perpendicular to the flow. A separation bubble or recirculating region (1–2 cm wide) formed behind the pectoral fin and extended along the entire trunk of the fish. The magnitude of the mean, local flow in this region was significantly less than that further away and its direction very close to the fish was likewise very different, predominantly upstream. The shear layer dividing the separation bubble from the external flow was fairly stable at 2 cm/s (Re 102), but very unstable and wave-like at 8 cm/s (Re103). These results show that fish body parts like the pectoral fin can significantly alter the local hydrodynamic stimulus field to the lateral line relative to ambient water motions only a few centimeters away.
P3.89 COOPER, R.L. *, TABOR, J., CHASE, R.J., University of Kentucky. Altered responsiveness to 5-HT at the crayfish neuromuscular junction: receptor up- & down-regulation.
Serotonin (5-HT)levels in the hemolymph of crustaceans has been implied to alter the assertiveness and aggression during social interactions (Huber et al., 1997; Sneddon et al., 2000). Pharmacological examination shows that m-CPP has agonistic functions in crayfish altering sensory drive into the animals ventral nerve cord (Yeh et al., 1996), thus suggesting the presence of one or both 5-HT1 and 5-HT2 receptor types. Based on evidence in other systems, one would suspect that chronically sustained 5-HT levels would results in a compensatory negative feedback regulation and/or that target tissues would diminish their sensitivity to high levels of circulating free 5-HT. Altered cellular activity as well the action of agonists or antagonists being bound to a receptor can induce regulation in the levels of functional receptors (Welner et al., 1989; Kokay and Mercer, 1997; Fone et al., 1998). For example it has been shown that 5-HT1A receptors will demonstrate desensitization when either an agonist or antagonist is present (Hensler and Truett, 1998). The purpose of our study is to address the issue of up- and down-regulation in the sensitivity of the responsiveness to exogenously applied 5-HT at the neuromuscular junctions (NMJs) of crayfish in which the animals have had either reduced endogenous 5-HT levels by enzymatic inhibition in the synthesis of 5-HT or have had a chronic presence of an agonist in their hemolymph. Injections of the 5-HT1 and 5-HT2 vertebrate receptor agonist, m-CPP, for 1 week resulted in a decreased responsiveness to 5-HT. The reduction of systemic 5-HT by injections of p-CPA, which blocks the synthesis of 5-HT, resulted in a supersensitivity of both tonic and phasic NMJs.Funding: NSF grants IBN-9808631 (RLC) & NSF-ILI-DUE 9850907 (RLC).
P1.59 COOPER, S.J.*, SAME, D.R., University of Wisconsin, Stevens Point. Ventilatory accommodation under cold stress in seasonally acclimatized black-capped chickadees.
Black-capped chickadees undergo seasonal acclimatization that is characterized by an increase in both basal and summit metabolism in winter birds compared to summer birds. Little is known about how the avian ventilatory system accommodates the large changes in rates of oxgyen consumption (VO2) between basal (BMR) and summit metabolism (VO2sum). We measured ventilation and VO2 under thermoneutral conditions and cold stress in seasonally acclimatized black-capped chickadees. Cold stress tests were conducted using a gas mixture of 79% helium and 21% oxygen (helox). Metabolic expansibility (VO2sum/BMR) was 5.5 in summer and 6.7 in winter. For summer birds, the increase in VO2 under cold stress was accommodated mainly by an increase in tidal volume (VT). For winter birds, the increase in VO2 under cold stress was accommodated by decreased respiratory frequency, an increase in VT and a significant increase in ventilatory oxygen extraction (EO2). The winter EO2 of 68.3% was significantly higher than summer birds (42.5%) and is the highest value so far documented in birds. There were no other significant differences in ventilation between summer and winter birds under thermoneutral or cold stress conditions. Our data suggests that changes in EO2 are involved with seasonal acclimatization to cold in black-capped chickadees.
65.1 CORLEY, L.S.*, STRAND, M.R., University of Wisconsin, Madison. Regulation of caste fate in the polyembryonic wasp, Copidosoma floridanum.
Striking morphological differentiation among individuals structures the complex societies found in insects such as termites, bees, and ants. Castes have also evolved in other insects such as aphids, thrips and polyembryonic wasps. Copidosoma floridanum is a polyembryonic parasitoid wasp that produces two castes during development from a single egg. Polyembryonic development results in a single brood containing approximately 1000 reproductive larvae that develop into adult wasps and 50 precocious larvae that function as soldiers. We examined how the single egg proliferates and responds to environmental factors to produce two castes in C. floridanum. We conducted transplantation experiments of wasp embryos from all developmental stages into unparasitized hosts from all developmental stages. By transplanting wasp embryos of a particular stage into different host environments, we partitioned the effects of the intrinsic properties of the embryos from the extrinsic factors (i.e.—the host environment) influencing caste fate. Our results indicate that both intrinsic and host environmental factors affect caste formation in this species.
10.4 COSTA, D.P.*, GALES, N.J, GOEBEL, M.A., Univ of California, Santa Cruz, Conservation and Land Management, Western Australi, AMLR National Marine Fisheries Service. The role of physiology in the behavior of diving mammals.
Diving animals offer a unique opportunity to study the role physiology in limiting behavior. An important component of the physiological capability of any diving animal is it's aerobic dive limit (ADL). The ADL has only been measured in a few species. The goal of this study was to estimate the aerobic dive limit from measurements of body oxygen stores and at sea metabolism. This calculated ADL was compared to measurements of diving behavior of individual animals of three species of otariids, the Antarctic fur seal, Arctocephalus gazella, the Australian sea lion, Neophoca cinerea and the New Zealand sea lion, Phocarctos hookeri. Antarctic fur seals dove well within the cADL. In contrast, many individuals of both sea lion species exceeded the cADL. Australian and New Zealand sea lions dove 1.4 times longer than the cADL. The tendency to exceed the cADL was correlated with the dive pattern of individual animals. In both Antarctic Fur Seals and Australian sea lions, deeper diving females made longer dives that approached or exceeded the cADL (P < 0.01, r2 = 0.54). Australian and New Zealand sea lions with longer bottom times also exceeded the cADL to a greater degree. The two sea lions forage on the benthos while the fur seals feed shallow in the water column. It appears that benthic foraging requires these animals to reach or exceed their aerobic dive limit.
14.1 COSTANTIO,D.*, KOZAK, K., LECAUDE, S., ALRUBAIAN, J., DORES, R.M., University of Denver, Colorado. Cloning of a proopiomelanocortin cDNA from the pituitary of the urodele amphibian, Aphiuma means.
The proopiomelanocortin (POMC) gene has been cloned from several anuran amphibians, however, the organization of this prohormone-coding gene had not been analyzed in a urodele amphibian. A degenerate primer was used to clone and sequence a POMC cDNA from the pituitary of the urodele, Amphiuma means. The cloning strategy involved the use of a 3'RACE procedure and a 5'RACE procedure. The open reading frame of the A. means POMC cDNA coded for a 267 amino acid precursor that contained the sequences of ALPHA, BETA, and GAMMA MSH, as well as ACTH, and BETAendorphin. The A. means POMC sequence was aligned to several anuran POMC sequences including Xenopus laevis, Spea multiplicatus, Rana ridibunda, and Bufo marinus, and to two lungfish POMC sequences (African and Australian). As expected, cladistic analyses placed the A. means POMC sequence as the sister group to the clade of anuran amphibian POMC sequences.This project was supported by NSF grant IBN-9810516.
P1.76 COSTANZO, J.P., JONES, E.J.*, LEE, R.E., Miami University, Oxford, OH, University Indianapolis, Indianapolis, IN, Miami University, Oxford, OH. Physiological responses to supercooling and anoxia in the hatchling painted turtle.
We investigated physiological responses to supercooling in hatchling painted turtles (Chrysemys picta), which remain in their natal nests over winter. These turtles are freeze tolerant, but also rely on supercooling to survive exposure to the lower temperatures occurring in nests during winter. We measured whole-body concentrations of lactate, glucose, glycerol, and ATP in turtles chilled for 5 days at 0, –4, or –6°C, or chilled for 19 days at –6°C. In a companion experiment we measured metabolite concentrations in turtles exposed for 1, 4, or 8 days to an anoxic environment. Chilling and anoxia exposure both resulted in an increase in concentrations of lactate and glucose, a decrease in the glycerol concentration, and no change in the ATP pool, suggesting that oxygen delivery and/or utilization is impaired in supercooled turtles. Anoxia tolerance may be an important preadaptation for surviving exposure to subzero temperatures in hatchling C. picta.
P1.9 COSTANZO, J. P.*, LITZGUS, J. D., IVERSON, J.B., LEE, R.E., Miami University, Oxford, OH, University South Carolina, Columbia, SC, Earlham College, Richmond, IN, Miami University, Oxford, OH. Cold hardiness and desiccation resistance in hatchling turtles.
North American turtles hatch in late summer and spend their first winter either on land or under water. Adaptations for terrestrial overwintering of hatchlings in northern regions, where winter thermal and hydric regimes are harsh, have not been systematically investigated in many species. We measured intrinsic supercooling capacity, resistance to inoculative freezing, and desiccation resistance in terrestrial and aquatic hibernators indigenous to northern (Terrapene ornata, Chrysemys picta bellii, Kinosternon flavescens, Chelydra serpentina) and southern (C. p. dorsalis, Trachemys scripta, Sternotherus odoratus, S. carinatus) locales. Supercooling capacity and inoculation resistance tended to be higher in the terrestrial hibernators, especially C. p. bellii, and terrestrial hibernators better resisted evaporative water loss. Most species tolerated the loss of a modest amount of body water, although some S. carinatus died during desiccation experiments. With the possible exception of T. ornata, turtles did not regain lost body water from wet soil and immersion in free water was required for rehydration; therefore, desiccation resistance is an important adaptation to terrestrial hibernation. Resistances to inoculative freezing and desiccation were directly correlated, perhaps because they are governed by the same morphological attributes.
55.4 COTTER, P.A.*, EVERSON, J. J., RODNICK, K.J., Idaho State University, Diagnostic Imaging of Idaho, Idaho State University. What comes in must go out:ventricular blood flow patterns in the rainbow trout.
Hemodynamic parameters in fish are often measured using invasive techniques, limiting the use of repeated measure experimental designs. We used high-resolution (10 MHz) echocardiography, and doppler analysis of sagittal images to determine ventricular filling (diastolic) and emptying (systolic) patterns in 3 body-size categories (400–500g, 600–800g, >1kg, n = 2/category) in hatchery-reared, anesthetized, Rainbow Trout (Oncorhynchus mykiss) at 14°C. Doppler analysis allows determination of both velocity (cm/s) and duration of blood flow (s) through atrioventricular and ventriculobulbar valves. Subtracting end-systolic from enddiastolic volume yielded stroke volume. We calculated flow (ml/s) through valves using stroke volume and diastolic/systolic time. Duration of ventricular systole (mean = 0.41s, SD = 0.07) was independent of body mass and approximately 2x that of diastole in all individuals. Flow (range = 0.9–4.2 ml/s) and blood velocity (range = 67.7–120 cm/s) of ventricular systole were approximately 50% that observed in diastole. In summary, despite size-dependent changes in stroke volume (range = 0.27–1.47 ml), the duration of systole and diastole, and heart rate remain relatively constant, suggesting compensatory mechanisms are involved in increasing cardiac output with increasing ventricle size. Electrocardiographic (ECG) data collected concurrently with echocardiographic/doppler imaging will help decipher the relative contribution of both atrial contraction and ventricular relaxation in cardiac blood flow patterns in the growing trout heart.
S6.2 COUGHLIN, D. J., Widener University, Chester, PA. A molecular mechanism for variations in muscle function in rainbow trout.
Rainbow trout provide an excellent model for the molecular analysis of muscle function. For several years I have studied a developmental shift in muscle kinetics and swimming performance in trout. At the parrsmolt transformation, red or slow-twitch muscle of trout undergoes a shift in contractions kinetics. The red muscle of younger trout parr has faster rates of activation and relaxation in isometric contractions and has a faster maximum shortening velocity (Vmax) than that of older trout smolts. Further, parr swim steadily at higher tailbeat frequencies than smolts. Molecular biological techniques can be used to examine the molecular basis for this developmental shift in muscle function. Because of the observed variations in Vmax, an ontogenetic shift in the muscle protein myosin heavy chain (MHC) may be responsible for changes in muscle kinetics. We examined the MHC protein with SDS-PAGE and through cloning and sequencing MHC mRNAs. SDS-PAGE revealed a significant shift in the pattern of MHC isoforms. Parr red muscle samples typically have 2–3 forms of MHC, while smolt samples have 1–2 forms. Densitometry reveals a statistical difference in the intensity of MHC bands between the two stages, suggesting a developmental reduction in MHC isoforms in trout red muscle. Three MHC mRNAs were subsequently cloned and sequenced, one each from red, white and ventricular muscle. Through the use of isoformspecific primer pairs, RT-PCR was used to determine the expression patterns of these three mRNAs in trout red muscle. Parr red muscle consistently expresses both white and red isoforms, and often the ventricular isoform, of MHC. As compared to parr, a greater proportion of the smolt red muscle samples expressed only the red muscle isoform. A shift in MHC expression provides a mechanism for the ontogenetic change in muscle function in rainbow trout.
26.2 COURTLAND, H.W-.*, WRIGHT, G. M., DEMONT, M. E., AtlanticVeterinary College, Atlantic Veterinary College, St. Francis Xavier University. Physical properties of noncollagenous lamprey cartilages.
Morphological and biochemical studies have demonstrated that lamprey cartilages are different from other vertebrate cartilages in that their major structural components lack collagen and elastin. Notable biochemical and morphological variations even suggest that a family of noncollagenous matrix proteins comprises the lamprey's cartilaginous skeleton. Yet, in spite of this knowledge, the mechanical properties of these cartilages remain a mystery. In order to further our understanding of cartilage structure-function relations, we conducted a series of stressrelaxation experiments on lamprey annular and pericardial cartilages. Strains of up to 15% were applied in compression (annular) and tension (pericardial). The applied strains and measured equilibrium stresses were used to determine the modulus of elasticity for these cartilages. Our results demonstrate significant differences between the stiffness of lamprey cartilages and other vertebrate cartilages (i.e., hyaline articular cartilage). In addition, there are noticeable differences in stiffness between the two lamprey cartilages.
19.2 COWART, J. D., University of Florida, Gainesville. Palatability of Pteraster tesselatus (Echinodermata: Asteroidea) eggs.
Risk of offspring mortality is a critical component of models concerning the ecology and evolution of life history traits in marine invertebrates. In these models, predation is generally assumed to be the most important cause of pre-settlement offspring mortality. Although few studies have directly investigated offspring susceptibility to predators, most models evaluating development assume that offspring of most species are palatable. Pelagic nonfeeding offspring are commonly large, conspicuous, energy rich, produced in small numbers, and lack apparent morphological defenses. Interactions between nonfeeding offspring and consumers are not well studied. However, recent studies have shown that pelagic nonfeeding offspring may benefit from the production of chemical defenses. This study investigated offspring palatability of the starfish Pteraster tesselatus. Members of the pterasterid family are unique because the adults secrete mucus over their aboral surface when attacked by predators. In addition, most species of pterasterids brood direct developing offspring within a specialized brood chamber called the nidamental chamber. P. tesselatus is unique because it has reevolved pelagic development. The eggs of P. tesselatus are large, energy rich, positively buoyant, bright orange, and exposed to pelagic predators. I hypothesize that the re-evolution of pelagic development resulted in the evolution of chemical defenses in the offspring of P. tesselatus. Preliminary results support this hypothesis by showing that the eggs of P. tesselatus are unpalatable to two species of northern pacific fish, Oligocottus maculosus and Gasterosteus aculeatus.
27.6 COX, D.E.*, BERTRAM, J.E.A., Florida State University. Hypothesis testing as a lab exercise: a simple walking study.
This paper describes a laboratory exercise designed to provide students with experience testing a hypothesis by systematically isolating and controlling determinant variables. The study involves the analysis of walking and is performed by the students on a subject from within their lab group. The study requires use of a motorized treadmill, tape measure, stop watch, personal cassette player and calculator. The exercise is designed to include factors that the students are familiar with, so they can focus on the isolation of parameters without being confused about the process they are investigating. However, the exercise will not turn out as they anticipate, meaning they will be forced to re-evaluate the assumptions that formed the basis of their original hypothesis. This exercise is designed for a college level course in exercise science, physiology or biology, but could easily be managed by a high school honors class with appropriate guidance.
P2.5 CRAWFORD, B. J.*, PANG, T., CAMPBELL, S. S., U. B.C. Vancouver, B. C. Development of the hyaline layer of the asteroid Pisaster ochraceus.
Embryos and larvae of the starfish Pisaster ochraceus are surrounded by a complex ECM layer called the hyaline layer (HL). A similar but less well organized ECM layer lines some regions of the larval gut. In material preserved with conventional fixatives to which anionic dyes have been added, the HL consists of three regions, a outer coarse meshwork (CM), a supporting layer (SL) and an intervillous layer (IV). Examination of material preserved by freeze substitution shows greater details, i.e. the SL is divided into three sub layers H1, H2, and H3 and has a boundary layer (B), consisting of short fibers which are and associated with its outer surface and project into the CM at right angles to the SL. Development of the HL begins at fertilization when exocytosis of the cortical granules releases ECM into the perivitelline space and elevates the fertilization membrane. Shortly after this plaques of dense material with attached fibers are present on the outer surface of the egg plasmalemma. Following this these plaques and fibers are associated with the tips of short microvilli suggesting that they may induce the microvillus formation. Next, the tips of some of the microvilli are joined by short regions of the H1 sub layer. Some of these H1 regions have short segments of boundary layer material associated with their outer surfaces while others are naked. Just prior to hatching, the H1 and B layers completely surround the embryo separating the developing CM and IV layers. Short segments of the H2 and H3 sub layers are also beginning to appear and extend to surround the embryo. Post hatching, the microvilli and all HL layers increase in thickness and density, particularly the H2, boundary and CM layers. The results suggest a sequential organization of HL components from ECM which is secreted into the perivitelline space. Supported by NSERC.
30.5 CROLL, G.A. *, MCCLINTOCK, J.B., University of Alabama at Birmingham. Sexual dimorphism, cheliped assymetry and selection pressure in Uca spp.
Left-right claw asymmetry occurs in a variety of decapod species. The asymmetries can be present in early development or arise during sexual differentiation. In Uca spp., males have a dimorphic enlargement of one of the two chelipeds. The larger cheliped has been associated with male reproductive success as a result of female selection or advantage in male-male combat. Because the enlarged cheliped occurs on either the right or left side, selection pressure could produce populations with right or left cheliped dominance. To ascertain whether such selection pressure is acting on Uca longisignalis, U. minax, and U. pugnax, populations of fiddler crabs from four North American marshes were sampled; two on the coast of the Atlantic Ocean, one on the Chesapeake Bay and one on the coast of the Gulf of Mexico. There were no significant differences in the proportion of right or left enlarged chelipeds within males of all sampled species or within marshes (p>0.05). Similarly, when male crabs were grouped arbitrarily into two major cheliped size classes (equal to or greater than 20 mm and less than 20 mm) the proportion of right or left enlarged cheliped individuals was similar among each of the size groups (p>0.05). Mean major propodus size for males was similar for individuals with either right or left cheliped dominance within each of the three species and four marshes (p>0.05). It appears that among these three species of Uca, there is no selection for males with cheliped enlargement on either the right or left side.
40.1 CROLL, S. L.*, WATTS, S. A., University of Alabama at Birmingham. The effect of temperature on feeding characteristics in two sympatric crayfish species.
Crayfish are an integral component of many freshwater habitats. They often impact the environment through vegetative grazing, burrowing activities, and predation. The red swamp crayfish, Procambarus clarkii (PC), and the white river crayfish, P. zonangulus (PZ), are commonly found in the southeastern United States and are important in commercial culture activities. Because of their ecological and commercial importance throughout these temperate regions, the effects of temperature on feeding characteristics and, consequently, production are of interest. Consumption of a formulated diet, apparent dry matter digestibility (ADMD), and carbohydrate and protein absorption were examined after exposure for 3 weeks at 8, 14, 20, 26, or 32 C. Sex-specific differences were generally not found in either species. At 32 C, PC consumed significantly more feed (30 % body weight per d) than PZ (4 % body weight per d); consumption did not vary between the species at all other temperatures. Consumption averaged 6 and 7 % body weight per d at 26 C in PC and PZ, respectively, a temperature near their reported thermal optimum. Consumption was minimal at 8 C. ADMD ranged from 55–75% regardless of sex, species, temperature, or rate of consumption. Carbohydrate absorption efficiency increased in both species from approximately 20 % to 70 % as temperature increased from 8 to 32 C. In contrast, protein absorption efficiency decreased from 45 % to 5 % as temperature increased from 8 to 32 C. PC and PZ maintain a relatively constant consumption rate at a wide range of temperatures, but species-specific differences at high temperatures suggest that PC will have a potential growth advantage. These data suggest further that the protein:energy requirements for these species change with temperature.
P1.90 CROSSLEY, D. A.*, BAGATTO, B. P. HICKS, J. W., ALTIMIRAS, J., University of California, Irvine, University of NorthTexas, University of California, Irvine, Goteberg University, Sweden. Changes in cardiovascular control mechanisms during the embryonic development of the American alligator, Alligator mississippiensis.
Several ectothermic vertebrates possess a unique cardiac morphology that provides the potential for differential perfusion of systemic and pulmonary vasculatures. The crocodilians represent one such group with the capacity to bypass the lungs, returning deoxygenated blood to the systemic tissues (R-L shunt). Numerous studies have investigated cardiovascular function and control in adult crocodilians; however, maturation during embryonic development remains unknown. This study determined changes in cardiovascular function and control during the embryonic development (from 30 to 72 days) of the American alligator. During development resting cardiovascular function changed markedly, with mean arterial pressure rising from approximately 1kPa half way through incubation to 3 kPa at hatch. Heart rate remained relatively constant over development rising slightly from 80 to 90 beats per minute. Control mechanisms were comprised primarily of adrenergic systems with no tonic cholinergic input evident during alligator incubation. Baroreflex responses could be elicited initially at 70% of incubation with a progressive rise in sensitivity. Collectively the data suggest that embryonic control of cardiovascular function differs from that known to be present in adult animals.
34.4 CROSSLEY, D. A.*, HICKS, J. W., BENNETT, A.F., University of California, Irvine. Postprandial changes in cardio-respiratory responses of the Savannah monitor (Varanus exanthematicus).
Cardio-respiratory control has been well characterized in numerous endothermic vertebrates, however our understanding of these systems in ectothermic vertebrates remains poorly understood. The purpose of this study was to thoroughly assess the cardiovascular and pulmonary responses to changes in ambient gas composition in the Savannah monitor, Varanus exanthematicus, in a fasted and fed state. Fasted animals exposed to graded hypoxia exhibited a ventilatory response characterized by an increase in Ve, Vt, fB. These changes were accompanied by a fall in arterial PO2 and PCO2 while arterial pH rose. In addition, hypoxia resulted in a progressive tachycardia but blood pressure remained constant. Graded hypercapnia produced an increase in both arterial PO2 and PCO2 while pH fell during each exposure. These changes were coupled with an elevation in all ventilatory parameters; however, cardiovascular parameters remained constant. 24 h after ingesting a standardized meal, baseline values of all measured parameters rose with the exception of arterial pressure and pH, which remained unchanged. Postprandial exposures to both the hypoxic and hypercapnic rÈgime produced responses in all measured parameters that were similar to that of the fasted animal. Thus it appears that the control mechanisms are unaffected by feeding in the Savannah monitor.
S5.10 CROWE, J.H.*, CROWE, L.M., University of California, Davis. Anhydrobiosis: a unique biological state.
Anhydrobiosis ("life without water") is a wide-spread phenomenon in all major groups of lower organisms. Anhydrobiotic organisms often contain as little as 2% water content. They persist in the dry state for lengthy periods, but when they are returned to water they rapidly rehydrate and resume active metabolism. The mechanisms underlying their ability to survive in this unique state are becoming well understood; virtually all such organisms produce disaccharides at high concentrations, most notably a disaccharide of glucose, trehalose. Trehalose has the ability to stabilize dry membranes and proteins, and, it is emerging, intact cells in the absence of water. This stabilization involves direct interaction between the sugar and hydrophilic residues in biomolecules, an interaction that confers upon the molecule a physical state that resembles the fully hydrated state. This interaction, which has come to be called the " water replacement mechanism" appears to be required for the stabilization. Recently, these findings have been applied to mammalian cells, and it is becoming possible to reduce these cells to a dry state, with excellent recovery, findings that are likely to have applications in clinical medicine. In the dry state, anhydrobiotic organisms show an arrest of metabolism, during which they appear not to age. When the cells are rehydrated, they resume active metabolism, but the life span is not shortened by the length of time spent in anhydrobiosis. The same appears to be true of mammalian cells dried with trehalose. We suggest that such an effective extension of the life span should have profound ecological and philosophical implications.
P3.47 CROWLEY, M.C.*, HATLE, J. D., ANDREWS, A.L., JULIANO, S.A., Illinois State University Inter-population differences in reproductive tactics in lubber grasshoppers.
For many organisms, a trade-off exists between reproductive timing (e.g. age at oviposition) and mass of reproductive output (e.g. number of eggs). Within a species, populations could be predicted to exhibit timing vs. output mass trade-offs that are adapted to their local environment. To test this hypothesis, we examined three populations of the clutch-laying grasshopper Romalea microptera. We predicted that grasshoppers from locations with relatively long growing seasons would have greater temporal reproductive plasticity and less plasticity in egg number. In contrast, grasshoppers from locations with relatively short growing seasons would have greater plasticity in egg number and less temporal plasticity. We used Florida (FL), Louisiana (LA), and Georgia (GA) hoppers as our long, intermediate, and short season populations, respectively. We reared three subsets of each population of grasshoppers with high, medium and low amounts of food available. For egg number, within each population, high-fed hoppers laid more eggs than low-fed hoppers. There were no significant differences in egg number among populations within a treatment. For time to oviposition, within each population, high-fed hoppers laid sooner than low-fed hoppers. In contrast to egg number, there were significant differences among populations within a treatment for age at oviposition. Both FL and LA medium-fed hoppers laid significantly later than GA medium-fed hoppers. There were no other significant differences among populations within a treatment. These data partly support our prediction that, in the trade-off between reproductive timing and mass output, long season hoppers will adjust reproductive timing and shorter season hoppers will adjust reproductive mass output.
S11.13 CRUSE, H.*, SCHUMM, M., University of Bielefeld, Germany. The influence of changing substrate conditions on swing movement trajectories.
Trajectories of swing movements of stick insects walking on different forms of substrates were studied. When walking on an inclined surface, the body is rotated around its long axis such that the vertical axis of the body is held more vertical than the direction perpendicular to the walking plane. A simulation shows that sense organs measuring leg joints are sufficient to explain this behavior. As a result of body rotation, swing movement trajectories have to be changed. In the downhill legs, the coxa-trochanter joint is more elevated than in the uphill legs. In the uphill legs, the femur-tibia joint is extended more which compensates for the smaller lift in the coxa-trochanter joint, leading to a higher extreme position in the uphill legs. By experimentally changing the starting position of a swing movement in vertical direction and in the direction parallel to body long axis, the trajectories cannot be predicted by an earlier hypothesis. A modified network allows for a description of the behavioral results. Swing movements depend on the width of the substrate. Walking on a wide treadwheel leads to different swing trajectories walking on a more narrow one. The contribution of the various leg joints is different depending on the substrate, suggesting an economical solution. If one joint is near its upper limit, the parallel neighboring joint may be activated to meet the goal of leg movement (motor equivalence). The form of the swing trajectory depends on the placement of the tarsus in the preceding stance. If the tarsus is placed flat on the ground, swing height is larger than when the tarsus grasps around an edge. Transition between different swing trajectories is not gradual. The form of the trajectory is determined by the current sensory input on a step by step basis.
P1.10 CUNNINGHAM, S.L.*, MARIS, R.C., Mansfield University of Pennsylvania. The employment of mini-biocells for the bioremediation of petroleum-contaminated soil over a two-week period.
The potential of petroleum spills possesses a significant threat to the natural environment. Such eminences have prompted the necessity for alternative methods of contaminated soil treatment. Studies at Mansfield University, over the last seven years, have centered around the breakdown of toxins by naturally-occurring microbes, or bioremediation. Investigations have utilized bacterial growth studies with drying and organic ashing in soil excavated from petroleum spills, and in artificially-maintained internal biocells. The present study has employed the use of mini-biocells. Six minibiocells (31 x 17 x 9 cm) were each filled with 1275 g of soil. These biocells were designated into two groups, open or closed, with control, gasoline, and diesel components. The petroleum-containing units were contaminated with 350 ml of the corresponding fuel. Daily samples were taken over a two week period to examine immediate effects of contamination on the soil ecosystem. Losses due to evaporation were monitored using the open and closed configurations. Obvious changes occurred in the gasoline biocells, unlike the diesel biocells which changed little due to the enhanced complexity. Bioremediation has shown to be a viable potential in the clean-up of petroleum-contaminated soil.
P3.8 CUNYUS, V.L., GOMEZ, A. L., JOHNSON, G. W., JOHNSON, J.D., IRWIN, L.N.*, University of Texas at El Paso. Taxonomic utility of random genetic variation in lizards.
We have used the randomly amplified polymorphic DNA (RAPD) technique to assess the utility of random genomic variation as a taxonomic trait at the Family level and below. We hypothesized that genomic similarity as measured by RAPDs would be greater within families than across families, and that the variation observed would predict phylogenetic relationships in agreement with traditional assumptions. DNA was extracted from members of the families Crotaphytidae (Crotaphytus collaris), Phrynosomatidae (Phrynosoma modestum, Sceloporus poinsetti, Urosaurus ornatus, and Uta stansburiana), Teiidae (Cnemidophorus tigris, C. tesselatus, and C. exsanguis), and Eublepharidae (Coleonyx brevis), amplified by PCR, and analyzed by agarose gel electrophoresis. Neiís index of similarity was 33+15% for 7 pairwise comparisons within families, and 1+11% for 19 pairwise comparisons across families, a highly significant (U = 18.5, p = 0.003) difference. Using a similarity matrix based on the RAPD data, a phenogram was constructed that conforms to traditional assumptions about phylogenetic relationships among and within these families, except that Crotaphytus collaris clustered among the Phrynosomatidae. These results support the validity of random genomic variation as a useful taxonomic trait at the Family level and below, and suggest that the RAPD technique may disclose some relationships different from those based on other characteristics. Supported by grants from the RCMI (G12-RR0814) and Bridges to the Future programs of NIH. We thank Dr. Elizabeth Walsh for significant help and advice.
P2.34 CUPP, P.V., Eastern Kentucky University. Spatial distribution and site fidelity in green salamanders, Aneides aeneus.
Individual green salamanders, Aneides aeneus (N=94) were captured and identified by the unique pattern of black spots on their heads. Individuals were then returned to the rock crevices from which they had been removed. Additional visits were made to the same areas in southeastern Kentucky over a four-year period with 50 animals (53%) being recaptured at least once. These 50 animals were recaptured 111 times, with the majority (96%)located in the same crevices in which they were first captured. Among males, larger individuals were recaptured more frequently. Also, larger males occupied the same crevices over a longer time than did smaller males. Further, observations of 337 males and 216 females indicate that adult A. aeneus occur singly in rock crevices. The spacing of A. aeneus in individual rock crevices and the fidelity of males to specific crevices provides additional evidence for territoriality in this species.
P2.69 CUSACK, B.J.*, NIEWIAROW-SKI, P.H., Community College of Allegheny County, University of Akron, OH. Variation in endurance in the fence lizard, Sceloporus undulatus: the effect of temperature, behavior, and morphology.
We measured the thermal sensitivity of endurance capacity, preferred body temperatures, activity body temperatures, and several morphological characteristics of Sceloporus undulatus from Nebraska and Ohio. Overall, S. undulatus from Nebraska had higher endurance than Ohio S. undulatus. Endurance measured over S. undulatus' range of field active body temperatures was statistically insensitive to temperature. Optimal body temperature for performance was statistically higher for the Nebraska population (mean = 31.26 C versus 29.86 C). Preferred body temperatures of both populations ranged approximately 29–34 C with a mean of 31.5±0.1 C. There was no difference between populations in the relationship between optimal body temperatures and preferred body temperatures. There was also no difference between populations in activity body temperatures (NE mean = 33.7 C; OH mean = 33.3 C). A previous study (Balk and Niewiarowski, 1998) found that S. undulatus from NE had lower maximal sprint speeds than S. undulatus from OH. Endurance and maximal sprint speed therefore appear to tradeoff at the population level between NE and OH. Furthermore, adult lizards from NE (high endurance, low maximal sprint speed) experience higher rates of mortality than adult lizards from OH (low endurance, high maximal sprint speed). This pattern is consistent with the hypothesis that endurance may be more important than maximal sprint speed in escaping predators, however there is currently no direct evidence to support such an hypothesis. More studies are needed to investigate covariation between locomotor performance parameters, life history traits and geographic variation in this species.
71.2 D'AMICO, L.J.*, DAVIDOWITZ, G., NIJHOUT, H.F., Duke University, Durham, NC, University of Arizona, Tuscon, Duke University, Durham, NC. Body size evolution in a laboratory strain of Manduca sexta: implications for studies in insect physiology and endocrinology.
The tobacco hornworm, Manduca sexta, has been used as a model organism for the study of insect developmental physiology and endocrinology for more than 30 years. Many of the connections between the growth and the endocrine physiology of the larva were established through a series of extensive studies done in the early 1970's. The present study compares those findings from the 1970's to our current collony when reared under identical conditions. We find that larvae are much larger now than in the 1970's, with a corresponding increase in the critical weight of the larvae. The threshold size for determining the final instar has decreased. These changes likely result from evolutionary processes that occurred while maintaining laboratory colonies. Given the use of morphological markers in staging larvae for physiological and endocrine studies, the changes in developmental characteristics highlighted here illustrate the need for investigators to determine if their staging techniques rely on relationships originally described in the 1970's.
50.6 DAHLGREN, T.G., WEINBERG, J.R., HALANYCH, K.M.*, Woods Hole Oceanographic Institution, National Marine Fisheries Service, Woods Hole, Woods Hole Oceanographic Institution. Phylogeography of the ocean quahog (Arctica islandica): influences of paleoclimate on genetic diversity and species range.
The ocean quahog, Arctica islandica (Linnaeus, 1767), is a commercially important bivalve found on continental shelves throughout much of the North Atlantic. To assess genetic subdivision in this species, we sequenced 385 nucleotides of the mitochondrial cytochrome b (cyt b) gene from 83 specimens collected from 12 localities between September 1998 and July 1999 (based on preliminary data, the Internal Transcribed Spacers, ITS, of the nuclear ribsomal repeat were not useful). The cyt b data delimited 11 haplotypes with 0.26%–8.1% nucleotide difference (coded by 36 variable nucleotide positions) among them. Only 3 haplotypes were detected in 39 specimens collected along the USA coastline, compared to 5 haplotypes from 9 Icelandic individuals. The western Atlantic populations ranging from Penobscot Bay (Maine, USA) to southern Virginia showed relatively low diversity and appeared genetically similar in that region. Based on the presence of shared haplotypes, AMOVA analyses, and phylogenetic reconstructions, Icelandic populations appear to be more genetically similar to western Atlantic populations than eastern Atlantic populations. Specimens from the Faroe Islands (n=4) show mixed affinities. These data are consistent with the hypothesis that a warm Holocene climatic optimum (circa 7500 BP), and not glacial refugia, shaped the present-day genetic structure in A. islandica.
22.2 DALEY, M.A., CARD, G., BIEWENER, A.A., Harvard University, Cambridge, MA. Effective mechanical advantage of the guinea fowl hindlimb during steady and variable speed running.
Animals live in an unpredictable environment and rarely move at constant speeds. Thus, muscle function under non-steady conditions (acceleration, deceleration) is a critical component of locomotor system design. Previous studies have suggested that, during steady speed locomotion, muscles function primarily to generate the force required to support body weight. However, it is not understood how these force requirements change during acceleration and deceleration. In order to address this, we examined changes in the Effective Mechanical Advantage (EMA) of the guinea fowl hindlimb using force platform and highspeed video recordings of the bird running at both steady and varying speeds. Limb EMA, defined as the total muscle force required per unit of ground reaction force, allows comparison of muscle force generation requirements during steady running, acceleration, and deceleration. We found that under all conditions, the majority of muscle force required to support the body is generated by the knee and ankle extensors, while the hip extensors produce less than 10% of the total force. EMA distribution among the joints changes during acceleration and deceleration, showing the greatest variation at the knee and ankle. During acceleration, knee extensors produce a greater percentage of the total muscle force, while during deceleration ankle extensors generate the majority of total muscle force. These changes in EMA likely reflect redistribution of force generation to muscles best suited for the prevailing locomotor requirements, allowing more efficient, rapid force generation during acceleration, and less costly absorption of energy during deceleration. (Supported by NSF IBN 9923699, and a Howard Hughes Medical Institute Predoctoral Fellowship)
P1.92 DARVEAU, C.- A.*, SUAREZ, R. K., HOCHACHKA, P. W., University of British Columbia, University of California, Santa Barbara, University of British Columbia. Evolution of energy metabolism: the case of hovering insects.
Hovering insects possess the highest mass-specific metabolic rate ever measured and are therefore an excellent model to study the evolution of metabolic pathways involved in energy production. We conducted a survey of the maximal activity of several enzymes as indicators of glycolytic capacity (Hexokinase, Phosphofructokinase), redox balance (Glycerol 3-phosphate dehydrogenase), and mitochondrial metabolism (Citrate synthase, Cytochrome c oxidase) in 19 species (4 genera) of Euglossine bees of varying size (varying from 50 mg to 1 g). A strong negative allometric relationship was observed for the activity of Hexokinase. The slope was similar to that of the oxygen consumption rate previously published for 9 species of Euglossine bees, which highlights the importance (maybe high control coefficient) of Hexokinase in these insects. Citrate synthase activity was also related to body mass, however, other factors (e.g. phylogeny) influenced the relationship. We analyzed data using phylogeneticaly independent contrasts and discuss the metabolic and evolutionary implications of these results.
P3.26 DAVIDSON, B. J.*, MOODY, W., SWALLA, B., University of Washington, Seattle. Metamorphic competence in the urochordates: cloning of a potential competence factor involved in EGF signaling.
We are interested in elucidating the signals involved in coordinating urochordate post-larval development. Through suppressive PCR subtractions of staged Boltenia villosa larval and juvenile cDNAs, we have isolated transcripts differentially expressed during urochordate metamorphosis. A transcript homologous to the EGF signaling protein Cornichon was isolated in a subtraction focused on the acquisition of metamorphic competence. We have named this transcript Benjam (Boltenia EGF neighboring/juxtapositioning/activating? molecule). In situ hybridizations demonstrate that Benjam is differentially expressed in the anterior papillary region of competent Boltenia larvae. Research in the urochordate Herdmania curvata has demonstrated that the anterior papillary region secretes the EGF protein Hemps, which is both necessary and sufficient for the initiation of metamorphosis. Cornichon was first isolated in Drosophila where it has a role in regulating the EGF signaling involved in establishing the dorsal/ventral and anterior/posterior axis during oogenesis. Recent work in yeast has established a role for Cornichon in the directed secretion of targeted vesicles. Our hypothesis is that expression of Benjam acts to potentiate Hemps signaling thereby allowing Boltenia larvae to respond to metamorphic cues. Further research into this role for Benjam in urochordate metamorphic competence will provide insight into the function of Cornichon, which has a crucial but undefined role in EGF signaling. Additionally, a better understanding of urochordate metamorphosis will provide a foundation for exploring the evolution of metamorphosis within the chordates.
64.1 DAVIDSON, B. J.*, MOODY, W., SWALLA, B., University of Washington, Seattle. Tunicate out of body experiences: extra-somatic cell migration and other insights and observations on urochordate metamorphosis.
We are investigating the morphological changes occurring during urochordate metamorphosis and the hormonal/transcriptional signals which coordinate this process. Initially, we have described a series of discrete morphological stages in the tunicate Boltenia villosa during the period of juvenile organ differentiation (the first two weeks after settlement.) These include a clear pattern of body-wall muscular differentiation which has been visualized through actin staining. This post-settlement pattern of differentiation may be coordinated by thyroid hormones, as TH blockers arrest juveniles early in development and TH levels may rise at the time when juvenile differentiation is initiated. We have also used subtractive hybridizations of mRNA expressed at times surrounding metamorphosis to investigate the differential transcription of genes which may coordinate metamorphic events. This technique has led to the cloning of a variety of immunological genes which seem to be transcribed around the time of settlement. The previously described migration of blood cells across the epidermis into the heamocoel at settlement may be related to this immune response. Careful observations of this migration has led to the detection of a group of mesenchymal cells which migrate through a tube connecting the anterior epidermis to the outside of the juvenile tunic. The function of this extra-somatic migration is currently under investigation. Through the detailed investigation of tunicate metamorphosis we are hoping to lay the groundwork for a better understanding of life-cycle evolution among the urochordates as well as how tunicate metamorphosis and post larval development is related to vertebrate embryogenesis.
P2.78 DAVIS, A.P.*, TOBALSKE, B. W., University of Portland, OR. Effect of distance on flap-bounding flight performance.
Previous studies suggest that flapbounding does not offer an aerodynamic advantage to birds flying at slow speeds. Therefore, we hypothesized that a bird using this flight style should quickly accelerate after takeoff and maintain or exceed the minimum aerodynamically attractive speed for its morphology. To test this idea, we studied wing and body kinematics in zebra finch (Taenopygia guttata) as they flew 2, 6, or 10 m within a flight corridor. Flights were recorded using high-speed video (250 Hz), and variation in flap-bounding behavior was measured among and within the flight distances. Average horizontal velocity increased as total flight distance increased. Our results support our hypothesis for flight distances greater than 2 m; flight speeds near 6 m/s were achieved during the middle of 6- and 10-m flights, and 6 m/s has been suggested elsewhere to be the minimum speed that would make flap-bounding aerodynamically attractive for a zebra finch. Wingbeat frequency (WBF) and percent time spent flapping (%FLAP) varied significantly among subsections of 6- and 10-m flights. However, averaging across entire flights, values for these two variables did not change with total flight distance. Compared to performance in a closed-section wind tunnel (at a higher altitude), zebra finch in free flight at 6 m/s exhibit lower %FLAP (50.2 vs. 68.7%) and higher WBF (28.5 vs. 24.3 Hz). These differences may be due to tunnel effects, the non-steady nature of relatively short-distance flight, or variation in air density between study locations. (supported by Murdock #99153)
P1.67 DAVIS, E.C., University of Kansas. Thermal stresses in the intertidal on acorn barnacles (Balanus glandula and Semibalanus cariosus).
Intertidal organisms live in an environment that has large thermal changes through the course of the tidal cycle. Acorn barnacles are found both on exposed rocks and in tidepools in the rocky intertidal. The thermal factors affecting Balanus glandula and Semibalanus cariosus in these two different intertidal habitats can be approximated from a mathematical heat flux balance model. The heat flux balance can be used to predict which factors most influence the temperature of a barnacle. The heat flux balance for an exposed barnacle on a rock shows that conduction is an important factor in the absence of evaporation. However, evaporation becomes the dominant term when it is added to the model under measured field conditions. Research was supported through a Friday Harbor Laboratories fellowship.
37.1 DAVIS, E.S., University of Wisconsin, Madison. Forced copulation as an evolutionary epiphenomenon.
To date, two general hypotheses regardingthe evolutionary origin of forced copulation (FC) have been proposed. The first and most widely accepted was proposed by McKinney et al. (1983), who posited that FC serves as a secondary reproductive strategy for paired males. Although not essential to their argument, the implication is that FC behavior arose as a result of selection for this behavior. The second, proposed by Gowaty & Buschhaus (1999) is the CODE hypothesis for the origin of sexual coercion behavior in birds. They posit that males create a dangerous and coercive atmosphere for females such that a femaleís only recourse is to solicit protection from a male in exchange for exclusive access to her for reproduction. Thus, they propose that sexual coercion arose as a mechanism to ensure female monogamy. It should be noted that these hypotheses are not mutually exclusive, as together they argue that FC has evolved as a polygynous male strategy, while at the same time helping to insure female monogamy. Studies presented here of mallards (Anas platyrhynchos) under semi-natural conditions lead me to propose a third hypothesis of the origin of FC behavior in waterfowl. That is, FC is an evolutionary epiphenomenon that initially arose because its underlying mechanism, high male testosterone (T) level, was sexually selected for another reason, namely mate guarding behavior. Note that this hypothesis posits that selection for mate guarding behavior precedes selection for FC behavior, in direct opposition to the CODE hypothesis. Here I will review the evidence for this hypothesis and its impact on the other two hypotheses.
65.4 DAVIS, G.K.*, JARAMILLO, C. A., PATEL, N.H., University of Chicago. Pax group III genes and the evolution of insect pair-rule patterning.
We have investigated the expression of homologues of the Drosophila Pax group III (PgIII) genes paired (prd), gooseberry (gsb) and gooseberry-neuro (gsb-n) in short germ insects. During Drosophila embryogenesis, prd acts as one of several pair-rule genes to define the boundaries of future segments via the regulation of segment polarity genes, including gsb. gsb, in turn, regulates gsb-n, a gene expressed later in the developing nervous system. In order to ascertain the role these genes play in the segmentation of short germ insects, we have taken a two-pronged approach. First, we have developed a polyclonal antibody which crossreacts not only to the products of the three fly genes but also to the homologous proteins of other insects. Using this antibody, we show that the embryonic expression of presumptive PgIII orthologues in the flour beetle Tribolium closely mimics the pattern in Drosophila. Second, we have isolated cDNAs of two PgIII orthologues from embryos of the grasshopper Schistocerca. Using both the cDNAs and the polyclonal antibody, we show that both genes are expressed in ectodermal stripes whose timing and appearance support a role for these genes in both defining and patterning segments. After the appearance of stripes of the segment polarity gene engrailed (en), both are expressed in coincident stripes of a one-segment periodicity. In a manner reminiscent of gsb and gsb-n, each of these stripes is restricted to the neuroectoderm and lies just anterior to its corresponding en stripe. Prior to the appearance of en, however, one of these genes is expressed in stripes of a two-segment periodicity before maturing into its segmental pattern. This early expression is more reminiscent of prd and provides for the first time evidence that pair-rule patterning is a facet of grasshopper segmentation.
8.4 DAVIS, M.C.*, SHUBIN, N.H., DAESCHLER, E.B., University of Chicago, University of Chicago, Academy of Natural Sciences of Philadephia. The evolution of the endochondral and dermal skeleton in fins and limbs.
The paired appendages of the two major clades of bony fish, actinopterygians and sarcopterygians, are composed of two separate skeletal units: A proximal endochondral skeleton and a more distal dermal skeleton. The relative contribution of these skeletal components to the fin is one of the key morphological differences between ray-finned and lobe-finned designs. Shifts in the pattern and development of each of these skeletal units can affect the function of the appendage as a whole. However, studies of the development of living fish cannot tell the whole story. Fossils reveal intermediate developmental and functional conditions that would not be predicted from a knowledge of recent taxa alone. Newly discovered fossils of the Devonian sarcopterygian Sauripterus show an extremely limb-like endochondral skeleton that is sandwiched between massive unjointed dermal rays. The endochondral elements of Sauripterus correspond in position to both the digits and mesopodium of tetrapods. The biomechanical function of the digit-like elements in Sauripterus is linked with the dermal skeleton; most movements of the fin would rely on the function of both skeletal components. This situation differs greatly from that seen in the earliest tetrapods. Tetrapods lack the dermal rays and, consequently, the digits interact directly with the substrate. Indeed, one of the main shifts in the origin of tetrapods may not be the origin of the autopodial bones, per se, but the loss of the dermal radials. This suggests that the loss of the dermal skeleton in appendage development is correlated with the evolution of mechanisms that patterned preexisting endochondral elements as an independently varying unit.
P1.94A DE LA PAZ, K.L., HOYT, D. F., WICKLER, S.J., COGGER, E.A., California State Polytechnic University, Pomona. Does muscle function explain preferred speed?
Horses prefer to trot at speeds that are the most economical. A possible explanation for this preference is at these speeds, muscle fibers are contracting more slowly and functioning more economically. The present study was undertaken to test the hypothesis that the lateral head of the triceps, an elbow extensor, shortens less, or more slowly, at preferred trotting speed than at those speeds above and below preferred trotting speed. Muscle length changes were measured using sonomicrometry and analyzed during the portion of stance phase when EMGs indicated the muscle was active and during which time there was an extensor moment at the elbow. Three Arabian horses (4–7 years old) were trotted at speeds from 2.5–4.5 m/s. Total positive strain (muscle shortening) and average positive strain rate (velocity of muscle shortening) were calculated at each speed. Total positive strain averaged 12% and showed no significant relationship with speed (R2=0.01, P>0.05). There was a positive linear relationship between speed and average positive strain rate in two of the three horses studied (R2=0.64 and 0.87, P<0.05). This increase in average positive strain rate resulted from a decreased time of contact. These observations are inconsistent with the proposed hypothesis. Supported by NIH 1 S06 GM53933.
44.6 DEAROLF, J. L.*, MCLELLAN, W.A., PABST, D. A., HERMANSON, J. W., Cornell University, UNC Wilmington, UNC Wilmington, Cornell University. Diaphragm muscle development in bottlenose dolphins (Tursiops truncatus).
Being born directly into an aquatic environment creates unique challenges for the breathing muscles of neonatal cetaceans. Not only must these muscles be active at the instant of birth to allow for gas exchange, but their activities must also be coordinated such that breathing takes place at the surface. Thus, we hypothesize that the breathing muscles of bottlenose dolphins, represented in this study by the diaphragm, will demonstrate adult morphologies at birth, as measured by the histochemical (myosin ATPase) and biochemical activities of their component muscle fibers. The fiber-type profiles of adult (64% slow-twitch) and neonatal (33% slow-twitch) dolphin diaphragms are found to be statistically different (F=48.02, p=0.002, df=5, n=6). In addition, there is a strong positive correlation (R-sq=0.98) between the fiber-type profile (percent slow-twitch fibers) of the dolphin diaphragm and total body length (TBL), a character that is used as a relative measure of age in dolphins. The results of the biochemical analyses support the correlation between fiber-type profile and TBL, demonstrating an increase in the expression of slow (type I) myosin heavy chain isoform with increasing body length. Thus, the diaphragms of neonatal dolphins are not well developed at birth (92–132 TBL). However, as the dolphin grows and increases its swimming and diving activities, the diaphragm matures and achieves adult morphology. Therefore, unlike dolphin locomotor muscles, which are well developed at birth, the diaphragm requires an extended period of postnatal development to achieve the adult fiber-type profile.
S3.4 DEBAN, S. M.*, O'REILLY, J. C., NISHIKAWA, K.C., University of Utah, Salt Lake City, University of Massachusetts, Amherst, Northern Arizona University, Flagstaff. The evolution of the motor control of feeding in amphibians.
We compared prey capture among salamanders, frogs and caecilians in a phylogenetic context to identify major evolutionary transitions of the motor control of amphibian feeding. The common ancestor of living amphibians was most likely a predator with a free-living aquatic larval life stage. A combination of visual, olfactory, tactile and lateral line (in water) cues triggered feeding. Suction feeding was used in water and jaw prehension on land. Feeding kinematics were influenced by both feedforward and feedback information. The primitive feeding behavior of salamanders most resembles that of this theoretical ancestor. Derived conditions within salamanders include 1) the evolution of elaborate, visually-controlled tongue protraction correlated with decreased lunging and 2) the reduction of vision in some groups and the concomitant dominance of other senses in triggering and modulating feeding. In the common ancestor of frogs, the tongue was short and lunging was necessary for prey capture. The visual system dominated other senses in triggering and modulating feeding and ampullary organs were lost, precluding the use of electrical cues. Derived conditions in frogs include 1) the repeated evolution of long tongues with a correlated decreased in lunging and 2) the dominance of olfactory and tactile sensory modalities in many burrowing, termite-eating species. Metamorphosed caecilians still use jaw prehension to capture prey. The ability to form visual images was lost ancestrally, as was the role of vision in feeding. Thus, the extensive variation seen in caecilian feeding kinematics is apparently driven by olfactory and tactile cues. Derived conditions among caecilians include the apparent use of electrical cues during feeding in aquatic species.
46.2 DEMAINTENON, M.J., University of Hawaii, Hilo. Patterns of reproductive system development in the caenogastropods; systematic and evolutionary implications.
The reproductive system is one of the most complex and variable of gastropod organ systems, and is often also the last organ system to develop. The level of anatomical variation of the reproductive system, coupled with its late development, renders it an interesting system to investigate for evolutionary changes in organogenetic patterns. Patterns of reproductive system organogenesis are compared in several representative caenogastropod species, relative to existing hypotheses of caenogastropod evolution. I am primarily interested in two questions: 1) How much temporal variation do caenogastropod taxa exhibit in the reproductive organogenetic sequence; and 2) How are patterns of temporal variation in the organogenetic sequence related to qualitative variations in adult reproductive anatomy between caenogastropod taxa? Paedomorphotic heterochronic events are thought to be common in gastropod evolution, however this hypothesis has been difficult to test. Comparison of organogenetic sequences within a phylogenetic framework allows the predominance of different types of heterochronic patterns to be addressed.
27.5 DEMES, B.*, CHIU, J., TRUONG, C., QIN, LARSON, S., SUNY Stony Brook. The role of the primate fibula in weight-bearing of the leg.
Among mammals, primates have relatively robust fibulae. We investigated the role of the primate fibula in weight-bearing in an in vitro study of the deformation of the two leg bones in a chimpanzee, baboon and human. Three rosette strain gauges were attached around the midshaft of the tibia and fibula in a leg preparation with muscles removed, but ligaments and joints intact. The legs were loaded in compression through the knee and ankle joints. The proximal femur was held upside down in a clamp, and the foot was tied to a plate that was subsequently loaded with weights. Loading cycles were repeated after cutting of the interosseous membrane, the proximal tibiofibular ligaments, and, ultimately, the fibula. In all three species, the predominant loading regimes for both bones is bending. In general, strains increase in the tibia and decrease in the fibula after cutting of soft tissues connecting the two bones.The changes in strain following cutting of the interosseous membrane are insignificant. Cutting of the ligaments has more of an effect. Strains increase incrementally and significantly in the tibia when the fibula is cut. In addition, the neutral axis of bending rotates from a mediolateral to a more oblique position. The described changes are more dramatic in the nonhuman primates. In comparison to humans, these species have more robust fibulae that are sandwiched beneath a flange of the tibial plateau rather than being attached to the lateral side of the tibia as in humans. These results indicate that the fibula has a significant role in weight-bearing of the leg in primates, that the interosseous membrane is probably unimportant in weight transfer between the two leg bones, and that inter-specific differences in bone size and positioning correlate with the observed strain pattern.
S14.3 DENVER, R.J., University of Michigan, Ann Arbor. Transcriptional regulatory networks induced by thyroid hormone during metamorphosis of the amphibian central nervous system.
Thyroid hormone (T3) induces multiple molecular, biochemical and morphological changes in the tadpole CNS.These changes prepare the animal for the transition from larval to adult life. At the cellular level, T3-induces cell proliferation, death, migration, process-elaboration and differentiation. Towards understanding the molecular basis for T3 action on the tadpole brain we isolated several genes that are directly regulated by T3 in Xenopus laevis. Ongoing sequence analysis places these genes into 6 general categories: 1) transcription factors, 2) cellular enzymes, 3) structural proteins, 4) cell cycle control proteins, 5) membrane receptors, 6) secreted signaling molecules. We analyzed the function of several immediate early genes that code for transcription factors. For example, mRNA for the basic transcription element binding protein (BTEB) is strongly induced by T3 in the premetamorphic tadpole brain. Brain BTEB mRNA level rises during metamorphosis and this rise depends on T3. BTEB mRNA expression in the adult brain is low and generally independent of T3. The gene is most highly expressed in the subventricular zone of the telencephalon, regions of the diencephalon and deep cellular layers of the tadpole tectum. We showed that Xenopus BTEB, like mammalian BTEB, binds to GC rich sequences and activates transcription from promoters containing multiple GC boxes. BTEB overexpression and misexpression studies in frogs and rodents suggest a role for this protein in neurite outgrowth and branching. This and other T3-inducible transcription factors likely play critical roles in the signal transduction pathways leading to the diverse changes in the tadpole CNS during metamorphosis. (supported by NSF grant IBN9724080)
S9.10 DENVER, R.J., University of Michigan, Ann Arbor. Evolution of the corticotropinreleasing hormone signaling system and its role in stress-induced developmental plasticity.
Post-embryonic development can be strongly influenced by the external environment. Amphibian tadpoles show strong responses to environmental signals, exhibiting continuous variation in the timing of metamorphosis.The most important environmental variable for a tadpole is water availability. We analyzed the ecological and physiological bases for the timing of metamorphosis in tadpoles exposed to habitat desiccation. Tadpoles of several species have been shown to accelerate metamorphosis when their ponds dry. Our ecological studies suggest that tadpoles use special senses to detect deleterious changes in their larval habitat. Habitat desiccation results in the precocious activation of the thyroid and the interrenal axes, the hormones of which drive metamorphosis. Several lines of evidence suggest that a common neuroendocrine signaling pathway involving the stress neuropeptide corticotropin-releasing hormone (CRH) determines the activation of the two systems. A role for CRH in regulating the pituitary-thyroid axis in addition to the pituitary-adrenal (interrenal) axis has been demonstrated in representatives of all vertebrate classes except mammals. The CRH signal is transduced by at least two receptor subtypes and may be modulated by a secreted binding protein. Taken together with ecological findings, our data suggest that tadpoles can respond adaptively to environmental deterioration by mounting a classical neuroendocrine stress response. Evolutionary conservation of the role of CRH in mediating developmental plasticity is suggested by recent demonstrations in mammals that CRH of fetal and/or placental origin determines the length of the gestational period and may be involved with precipitating preterm birth. (Supported by NSF grant IBN9974672)
42.2 DESROCHERS, D. M.*, NISHIKAWA, K.C., Northern Arizona University, Flagstaff. Hypoglossal sensory feedback control during feeding in the toad, Bufo alvarius.
This study explores the role of hypoglossal sensory feedback during feeding in the toad Bufo alvarius. Prior studies indicate that sensory feedback from the hypoglossal nerves can trigger inhibition of both tonic and phasic activity of the jaw levator muscles. Temporary inhibition of the jaw levators allows the jaw depressors to produce rapid mouth opening. Following bilateral hypoglossal transection, the levators and depressors fire simultaneously, preventing mouth opening during feeding attempts. Utilizing unilateral rather than bilateral hypoglossal transections, coupled with high-speed digital videography and EMG recordings from the jaw levators and depressors, I have further investigated hypoglossal feedback control of the anuran jaw musculature. Preliminary data show that while the mouth opens following unilateral transection, the velocity of mouth opening and the maximum gape angle are reduced. These results suggest that transection of the hypoglossal nerve on one side prevents the inhibition of tonic and phasic activity of the jaw levators only on that same side. Hence, on that side of the jaw, the levators and depressors may be firing simultaneously, resisting the efforts of the contralateral depressors to open the mouth and therefore reducing the speed and maximum gape angle of mouth opening. According to this scenario, each hypoglossal nerve carries information back to the central nervous system in a unilateral fashion. Nerve staining studies are currently being conducted to further test this hypothesis.
43.3 DEUFEL, A.*, CUNDALL, D., Lehigh University, Bethlehem, PA. Feeding in stiletto snakes.
Stiletto snakes (Atractaspis) resemble vipers in having a short maxilla bearing a long fang associated with a large venom gland. Previous studies of Atractaspis have described an unusual envenomation strategy in which one fang is unilaterally everted from the closed mouth and stabbed into the prey by a posteroventral jerk of the head. Prior anatomical descriptions suggest that the head of Atractaspis is designed for increased cranial kinesis through liberation of both ends of the pterygoid. We combined video records of A. bibroni feeding on live prey inside a narrow tunnel with electrical stimulation of anesthetized snakes and dissection of preserved specimens to show that the apparent design for increased cranial kinesis is constrained minimally by maxillaryprefrontal relationships that limit pterygoid movement. Liberation of the palatine from the pterygoid precludes prey transport using the "pterygoid walk" because of the absence of a palatine protraction mechanism. Atractaspis has to rely on a relatively inefficient transport mechanism in which the snake forces its head over the prey with lateral rotations around a vertical axis. As the prey enters the esophagus A. bibroni switches to bilateral head and anterior trunk extension and compression, a mechanism that can make use of the palatine teeth. It remains unresolved how an upper jaw with high kinetic potential of the medial elements could evolve together with a lateral upper jaw with limited kinetic potential. Nevertheless, the unusual feeding apparatus of Atractaspis appears to be ideally suited for prey capture in small spaces.
54.1 DEVRIES, A.L.*, CHENG, C.-H.C, University of Illinois. Freezing avoidance strategies differ in Antarctic and Arctic fishes.
Notothenioid fishes in Antarctica freeze at approximately –2.3°C. One degree of this freezing point depression is primarily due to NaCl, while the remainder is due to antifreeze glycoproteins (AFGP) and a recently discovered antifreeze potentiating protein (AFPP). AFGPs are present in the blood at 30 to 40 mg/ml while AFPP ranges from 2 to 4 mg/ml depending on the species of notothenioid. Only the antifreeze activity of the larger AFGPs 1–5 appeared to be potentiated, while the smaller AFGPs 7 and 8 are not. Thus fishes living in very icy shallow water like Pagothenia borchgrevinki have lower levels of AFGP 1–5 and high levels of AFPP, while Trematomus loennbergi living at 500 meters where the cold water lacks ice have high levels of AFGP 1–5 and low levels of AFPP. This relationship appears to correlate with depth and the amount of ice in the fishes environment. Arctic gadid fishes have freezing points between –1.9 and –2.1°C in the winter and also have AFGPs similar in size, composition and amount to the notothenioids but they do not have AFPP. There is no evidence of any other macromolecular antifreeze compound and thus the slightly elevated blood salt concentrations and the AFGPs appear to account for their low freezing points and freezing avoidance. In contrast, in the Antarctic notothenioids, the combination of elevated salt concentration (250mM), AFGPs and AFPP is responsible for the freezing avoidance.
S9.11 DHABHAR, F.S., Ohio State University. Stress and the augmentation of immune function.
Stress may be defined as a sequence of events, that begins with a stimulus (stressor), that is recognized by the brain (stress perception), and which results in the activation of physiologic systems within the body (stress response). Many evolutionary selection pressures are stressors, and one of the primary functions of the brain is to perceive stress, warn the body of danger, and enable an organism to respond. We hypothesized that under acute conditions, just as the stress response prepares the cardiovascular and musculoskeletal systems for fight or flight, it may also prepare the immune system for challenges (e.g. wounding) which may be imposed by a stressor (e.g. an aggressor). Initial studies showed that acute (2h) stress induced a significant trafficking of immune cells to the skin. Since the skin is an organismÍs major protective barrier, we hypothesized that this leukocyte redistribution may serve to enhance skin immunity during acute stress. We tested this hypothesis using the delayed type hypersensitivity (DTH) reaction, which mediates resistance to various infectious agents, as a model for skin immune function. Acute stress administered immediately before antigen exposure significantly enhanced skin DTH. Adrenalectomy (ADX) eliminated the stress-induced enhancement of DTH while administration of physiological doses of corticosterone and/or epinephrine to ADX animals enhanced skin DTH in the absence of stress. These studies showed that changes in leukocyte distribution and circulating stress hormones are global mediators of the immunoenhancing effects of acute stress. We recently identified gamma interferon as a local cytokine mediator of a stressinduced immunoenhancement. Our results suggest that during acute stress the brain sends preparatory warning signals to the immune system just as it does to other fight/ flight systems of the body.
S11.7 DIAL, K.P., WARRICK, D. R.*, BUNDLE, M.W., University of Montana, Minot State University. Stability and maneuverability in avian flight: keeping a steady head with a thrashing body and a twisted neck.
Popular models of avian maneuverabilitybased on steady-state assumptions and parameters such as wing loading fail to describe the full ecological and evolutionary import of maneuvering performance, particularly during low speed, flapping flight. Previous studies revealed that in this key flight regime maneuvering is saltatory, and involves authoritative use of velocity-generated force asymmetries developed during flapping. The effectiveness of this mechanism in maneuvering is largely independent of wing loading; however, low wing loading would result in reduced stability in turbulent conditions. Thus, the quick use of strong aerodynamic forces, as well as the gyroscopic action of flapping wings are likely important factors for maintaining stability, especially for small, lightly wing-loaded birds. Equally important may be a bird's ability to spare its head from the repeated shocks of saltatory locomotion. Data from x-ray film of magpies in wind tunnels, and light film of pigeons recovering from handler-induced rolls shows that birds isolate their visual and vestibular systems, presumably via cervical reflexes, from the vertical movement and accelerations of the body during flapping flight, and the angular movement and accelerations occurring during rolling maneuvers. Pigeons equipped with neck braces that reduced their head's normal three-hundred degree range-of-rotation to thirty degrees refused to or could not fly; pigeons with head movement restricted to seventy degrees had difficulty maintaining equilibrium and recovering from handler-induced banks. The neural integration of visual, vestibular, and proprioceptor inputs required for the control of maneuvering and maintenance of straight and level flight has not been extensively studied, although such integration must have been an essential step in the evolution of fully volant species.
22.3 DIAL, K.P., University of Montana. On the origin and ontogeny of bird flight: developing wings assist vertical running.
Discussions on the origin of avian flight fall into two philosophical camps: arboreal (tree-down) or cursorial (ground-up) hypotheses, both of which are dominated by paleontological evidence that fails to adequately address logical incremental adaptive stages necessary to achieve fully developed flight mechanics. Here, I present a new model based on novel behavioral and morphological data obtained during post-hatching development of precocial gallinaceous birds. This model offers a solution to the impasse of previous scenarios on the origin of avian flight and differs from the traditional cursorial thesis. Daily progress of locomotor performance (e.g., vertical and horizontal accelerations of flight and terrestrial locomotion) and morphometrics of wing development (e.g., wing loading, feather growth) of three species (Chukar Partridge, n=10; Japanese Quail, n=10; and Ring-necked Pheasant, n=2) from hatching to adult stage were obtained using high-speed video (60–250 Hz) and Doppler radar. To escape being handled, even one-day-old chicks exhibited the following locomotor behavior: they jumped vertically, vigorously beat their featherless forelimbs, and surprisingly swung their hind limbs through an arc similar to that used during over-ground running. Throughout development partially formed wings develop significant aerodynamic forces that assist the legs. This enables birds to "run vertically" achieving substantial heights against rough surfaces such as rocks, cliffs, and tree trunks. This "Assisted Vertical Running Hypothesis" appears consistent with evidence from fossil data and provides incremental adaptive plateaus, as revealed by ontogenetic trajectories, necessary to achieve fully developed avian flight mechanics as observed in living species.
51.5 DICKEY, B., University of Kentucky. Prediction and description of interaction patterns in social dominance structures.
Though social dominance hierarchies have been demonstrated and studied in a wide variety of vertebrate and invertebrate taxa, no models exist that explain or predict which animals should interact aggressively within a hierarchy. Data from empirical studies of social dominance are often presented in matrices that summarize which animal won the interactions between each pair of individuals. Many of these matrices contain identifiable patterns of interactions; for instance, interactions may be clustered along the diagonal of the matrix suggesting that individuals prefer to interact with others of equivalent rank. I present a game theoretic model that predicts this and other patterns, depending on the differences in benefits between different ranks in the hierarchy, and the distribution of traits that signal resource holding potential between individuals. The predicted patterns are then compared to empirical data using a statistical approach that permits comparison of matrices. This comparison improves our understanding of the link between social structure, benefits of rank, and traits that signal resource holding potential in natural groups.
S11.10 DICKINSON, M.H., University of California, Berkeley. The structure and function of flight trajectories in freely-flying fruit flies.
Without buoyancy or a solid horizontal plane for support, stability is of crucial importance to flying animals. Further, for animals that rely on spatially complex sensory cues for food search, mating, or predator avoidance, stability is required not only to keep the locomotor machinery in an appropriate orientation, but also to keep body oscillations from contaminating sensory signals. My laboratory has been studying the flight behavior of fruit flies, highly maneuverable organisms that rely on rapid sensory-motor feedback, and not passive mechanisms, for their robust stability. The flight paths of fruit flies consist of straight sequences interspersed with rapid saccadic turns, during which the animal quickly changes its heading by roughly 90 degrees. While flies are thought to rely heavily on visual feedback in flight control, evidence suggests that during the straight flight sequences they fly under the exclusive control of their halteres, mechanosensory structures that act as an inertial guidance system. Since mechanosensory cells are capable of faster response dynamics than photoreceptors, feedback from the halteres can tune the stability reflexes much more sharply than could feedback from the eyes. The saccades appear to represent fixed action patterns, the magnitude of which does not depend upon prior visual experience. The visual system does, however, determine the direction and timing of saccades. During straight flight, the visual system appears to integrate optic expansion, triggering a collision avoidance saccade when the expansion reaches a critical threshold. The role of the straight flight sequences may be to stabilize gaze during this integration process in order to minimize the errors introduced by body oscillations. Thus, the involuntary inertial stability system may play an important role in voluntary, visually-guided behaviors.
17.2 DINKELACKER, S.A.*, WILSON, T. P., HOWARD, J. H., Frostburg State University, George Mason University, Humboldt State University. Spatial ecology of syntopic bog (Clemmys muhlenbergii), spotted (Clemmys guttata) and snapping (Chelydra serpentina) turtles in Maryland.
I examined differences in home ranges among syntopic species of turtles occurring within a 3-ha wetland in Carroll County, Maryland. I attached radio transmitters to the carapaces of bog (Clemmys muhlenbergii), spotted (Clemmys guttata), and snapping turtles (Chelydra serpentina) and located each individual twice a week during the summer of 1999. I compared minimum convex polygon and adaptive kernel home-range size estimates and average daily movements among species using one-way ANOVA. I plotted all home ranges for each individual of all three species to assess total area used and spatial overlap within and among species. Spotted turtles had significantly larger home ranges than bog and snapping turtles. Spotted turtles had significantly greater average daily movements than bog turtles but not snapping turtles. Home ranges of bog turtles exhibited the greatest amount of intraspecific overlap (75.1%) and those of snapping turtles the least (15.4%). Spotted turtles overlapped the majority of the total area used by bog turtles (79.6%) and snapping turtles (64.4%). Interestingly, bog turtles only overlapped 19.5%, and snapping turtles only overlapped 8.0% of the total area used by spotted turtles. Comparisons of homerange sizes, avaerage daily movements and spatial overlap among the three species suggest that spotted turtles require more space to suport resource requirements at this site.
P3.36 DIOGO, R.*, OLIVEIRA, O., PARMENTIER, E., CHARDON, M., VANDEWALLE, P., University of Liëge, Belgium. The origin and transformation of catfish (Teleostei: Siluriformes) palatinemaxillary system: an example of adaptive macroevolution.
The adaptive value of siluriform barbels in muddy waters dwellers and nocturnal fish is evident and was moreover demonstrated experimentally. The maxillary ones are characterized by their connection to a mobile mechanism, the palatine-maxillary system (PMS), which is constituted by the maxillary, the palatine and more or less specialized ligaments and muscles responsible for their movements. Siluriform sister-groups (Gymnotiformes and Characiformes) do not have barbels at all and do not present any structure prefiguring barbels, particularly the maxillary barbels, which are the only ones present in the most primitive catfishes, the diplomystids. In fact, catfish PMS is based on two basic siluroid synapomorphies: 1) a skeletal uncoupling between the palatine bone and the the rest of the suspensorium; 2) a muscular uncoupling of the adductor arcus palatini, leading to the differentiation of the extensor tentaculi muscle, which is associated with the abduction of the maxillary barbel. So, unless improbably well preserved fossils would be described in the future, a gap will remain between the diplomystids and the gymnotiforms and characiforms. However, departing from the Diplomystidae, it seems possible to follow evolutionary lines leading to more specialized PMS types. Our study focus precisely on the evolution of the PMS among catfish. For each morphological transformation, the way it was realized is hypothetized and the probable adaptive advantage it brings is analysed.
P1.55 DOELLER, J. E.*, KRAUS, D. W., University of Alabama at Birmingham. Sulfide-mediated feedback inhibition of endogenous substrate oxidation in Geukensia demissa gill mitochondria.
Gill mitochondria from Geukensia demissa, a marine mussel from high sulfide sediments, exhibit sulfide-supported respiration with an ADP/O ratio near one. In vivo, sulfide-mediated gill oxygen consumption is three times higher than control at the same ciliary beat frequency, consistent with a change in mitochondrial ADP/O ratio from 3 to 1, and suggesting a change in substrate use from endogenous carbon to sulfide. Carbon-supported mitochondrial respiration declined incrementally following successive sulfide additions, suggesting possible inhibition of endogenous substrate oxidation by endproducts of sulfide metabolism. These numerous endproducts include thiosulfate and sulfite. Although thiosulfate alone had little effect on mitochondrial respiration, sulfite appeared to lower both state 3 and state 4 respiration. Therefore, mitochondrial substrate use may be subject to feedback control by sulfide metabolic endproducts. Supported in part by NSF IBN9219658 and IBN9728409.
P1.19 DOUGHERTY, B.E*, MCNAMER, A.N., CROCKETT, E.L., Ohio University, Athens. Inverse compensation for fluidity in mitochondrial membranes from thermally acclimated earthworms.
Exposure to low temperature typically results in changes at many levels of biological organization including adjustments in both chemical and physical properties of biological membranes. We compare membrane fluidities in enriched mitochondrial preparations from the body wall of the earthworm (Lumbricus terrestris) after four weeks of acclimation to 5 and 15°C. Membranes from 5°C-acclimated worms are more ordered than membranes from 15°C-acclimated animals with significantly greater polarization values at all but one temperature measured with the fluorescent probe DPH. At physiological temperatures polarization values are 0.22 and 0.15 for 5- and 15°C-acclimated worms, respectively. Although reports of inverse compensation of fluidity (greater membrane order in cold-bodied animals compared with warm counterparts) are relatively rare, inverse compensation in the earthworm is accompanied by changes in the metabolic status of the animal. Supported, in part, by the Honors Tutorial College at Ohio University.
S6.8 DRUCKER, E.G., University of California, Irvine. Experimental hydrodynamics of fish locomotion: functional insights from wake visualization.
The fins of fishes are sophisticated control surfaces that play important roles in stabilization and propulsion of the body during locomotion. Despite a century of active investigation into the mechanisms of fin function, there remains one critical area in which progress has been limited: analysis of the physical interaction between the animalís propulsor and the aquatic medium. This paper reviews current biomechanical research employing a new flow visualization technique, digital particle image velocimetry (DPIV), adopted from the field of fluid mechanics. This method allows experimental measurements of water velocity flows in the wake of freely swimming animals, and thereby enables direct investigation of the hallmark of fluid force production (vorticity). Emerging from recent applications of DPIV in research on fish swimming are findings with general significance for the study of aquatic locomotion: (1) DPIV is an effective tool for measuring the reaction forces on swimming animals. From rates of momentum transfer and vortex geometry, both the magnitude and orientation of wake forces can be determined to gain insight into the mechanisms of propulsion. (2) Three-dimensional analysis of wake flow is critical. Flow patterns in perpendicular sections of the wake reveal a hydrodynamic force balance on steadily swimming fish, a result validating the DPIV approach. (3) Fishes can adjust the structure and strength of their wake in response to varying locomotor demands. Multiple fins are employed simultaneously and independently to control locomotor force during both unsteady maneuvering and steady swimming across a range of speeds. For future work, DPIV holds considerable promise for illuminating the dynamics of biological fluid flow and for allowing functional interpretation of evolutionary trends in propulsor design.
2.4 DRUCKER, E.G.*, LAUDER, G.V., University of California, Irvine, Harvard University, Cambridge, MA. Function of the teleost dorsal fin: experimental analysis of wake forces in sunfish.
A major structural transformation characterizing the evolution of teleost fishes is the elaboration of the dorsal fin into anterior spiny and posterior soft-rayed portions. As yet, however, there are no hydrodynamic data on the functions served by these distinct fin surfaces. In order to initiate study of the locomotor repertoire of the teleost dorsal fin, we examined the wake of bluegill sunfish (Lepomis macrochirus)during steady swimming at low and high speeds, and while turning in response to a visual stimulus. Patterns of water flow within frontal-plane sections of the dorsal fin wake were measured using digital particle image velocimetry (5 W laser, 250 Hz video framing rate) and locomotor forces were estimated from rates of momentum transfer. For fish 21 cm in length (L), neither the spiny nor soft dorsal fins shed detectable vorticity at 0.5 L/s, indicating that they do not play an active role in propulsion at this low speed. At higher speeds, however, the dorsal fin is recruited to supplement locomotor forces exerted by the pectoral and caudal fins. At 1.1 L/s, continuous oscillation of the soft dorsal fin introduces paired counterrotating vortices into the wake.The thrust associated with the dorsal finís momentum jet is on average 24% of the total thrust developed by all fins. During turning maneuvers, the soft dorsal fin exerts laterally oriented forces that exceed thrust forces by a factor of 1.7 on average. The dorsal fin, therefore, plays propulsive roles both in translating the body during steady swimming and in exerting torque around the bodyís center of mass during unsteady locomotion. This study documents the ability of teleost fish to use simultaneous, independent action of multiple fins for the control of vorticity and for the modulation of locomotor force.
P3.37 DRUZINSKY, R.E., Governors State University, IL. Sciuromorphy and protrogomorphy in extant and fossil rodentia.
It has long been recognized that sciuromorphy, in which the anterior lateral masseter muscle originates from an expanded bony plane on the rostral surface of the anterior root of the zygomatic arch, evolved more than one time during the evolutionary diversification of rodents. Arguments for multiple origins of the sciuromorphic condition are usually based on the necessity of deriving sciuromorphy independently in disparate clades within the Rodentia. However, it is clear that careful study of the masticatory apparatus also demonstrates that sciuromorphy in the Sciurids is anatomically different from sciuromorphy in Geomyids. Anatomical study of Aplodontia, the only extant Progtrogomorph, indicates that Aplodontia shares charaters of the jaw musculature with the Sciurids that it does not share with the Geomyids. Examination of early rodents also demonstrates that more than one type of sciuromorphy and progtrogomorphy may be found in the fossil record. Oligospermophilus and Cedromus are fossil sciurids that, as described by Korth and Emry (1991) exhibit a "unique zygomatic structure" in-between sciuromorphy and protrogomorphy. These specimens clearly have attachment areas for the superficial masseter and lateral masseter similar to those of the Aplodontia/Sciurid clade. In contrast, the Eocene rodent Sciuravus nitidus, which has been described as a primitive sciuromorph or protrogomorph (Dawson, 1961), has attachment areas for the masseter muscles that are distinctly different from the Aplodontia/Sciurid clade, and more similar to the extant Dipodoids. Thus, anatomically there is more than one kind of sciuromorphy and even more than one kind of protrogomorphy. And classic protrogomorphy, as found in Paramys and Aplodontia, is probably primitive only for Ischyromyids, Sciurids, and Aplodontids.
P2.88A DRUZISKY, K.*, BRAINERD, E.L., University of Massachusetts. Buccal oscillation in the aquatic turtle Platysternon megacephalum.
Buccal oscillation has been demonstrated in all major groups of vertebrates except mammals (Brainerd, 1999). Using blowhole pneumotachography and video, we examined above-water buccal oscillations in an aquatic turtle, Platysternon megacephalum. In this study, we were able to distinguish between oscillation and ventilation based on tidal volume and sequence of exhalation and inhalation phases. The mean tidal volume for oscillations was found to be about 1/5 the tidal volume of lung ventilation. For ventilation, we recorded expiratory tidal volumes of 6.251 ± 0.85ml air, 5.645 ± 0.802 ml air, and 6.523 ± 0.829ml air for three individuals respectively. The oscillatory tidal volumes recorded were 1.315 ± 0.4931ml air, 1.208 ± 0.439 ml air, and 0.953 ± 0.569ml air. Oscillations also occur as inspiration/expiration sequences in contrast to the expiration/inspiration sequence of ventilation. Through simultaneous measurement of hyoid depression and airflow, we see a temporal correlation between hyoid movement and airflow during buccal oscillations and also a small hyoid depression at the start of respiratory exhalation. In examining the relationship between oscillatory and ventilatory events, preliminary data suggest that the two behaviors are independent with no fixed phase relationship. We have found that ventilation often interrupts the expiratory phase of oscillation thus overlapping the two behaviors. The data show ample variation in the pattern and individual volumes of oscillations with periods of large continuous oscillation interspersed with few breaths and periods of smaller oscillation more equally dispersed among breaths. Periods of ventilation only were recorded as well. The variation suggests the possibility of multiple functions of buccal oscillation.
27.2 DUDEK, D.M.*, FULL, R.J., University of California, Berkeley. Spring-like behavior of the legs of running insects.
The dynamics of many terrestrial organisms during running are similar to those of a bouncing spring-mass system. This observation has led to the search for spring-like behavior in the tendons of mammals. The dynamics of running cockroaches have been modeled as a spring-mass system, but the location of spring-like elements, if they exist, remains a mystery. Cockroaches have sprawled postures with joint axes oriented vertically resulting in the possibility of a passive, exoskeletal leg spring. Therefore, we determined the mechanical impedance (the time-dependant resistance of a material to deformation) and resilience of the metathoracic limb of a cockroach ( Blaberus discoidalis) using dynamic oscillations. The hind limb was removed and secured in an orientation consistent with that of a running animal. The leg was oscillated in the dorsoventral direction (orthogonal to the plane of rotation for the joints) and induced forces recorded. The resulting force-displacement relationships were non-linear and similar in many respects to the stress-strain curve for spider legs (Blickhan, 1986). As much as 50% of the energy used to displace the leg was stored as elastic strain energy and returned. While the relative importance of viscous damping decreased with increasing oscillation frequency, the impedance of the leg increased up to a frequency of 12 Hz. At frequencies above 12 Hz, the impedance of the leg remained constant. Interestingly, the stride frequency of running cockroaches increases with speed up to its preferred stride frequency, which is between 10–14 Hz. At faster speeds, stride frequency remains constant. Taken together, these results suggest that the effects of passive structures are significant and could allow the leg to act as a damped spring during locomotion. Supported by ONR N00014-98-1-0669.
S11.6 DUDLEY, R., University of Texas at Austin. Mechanisms and implications of animal flight maneuverability.
The axial and torsional agility of flying animals derives from interactions between aerodynamic force production and the inertial resistance of the body to translation and rotation, respectively. Anatomical and allometric features of body design thus mediate the rapidity of aerial maneuvers. Both translational and rotational responsiveness to accelerations-decrease with increased total mass. The relatively heavy wings of volant vertebrates render their wing and body moments of inertia of comparable magnitude. By contrast, insect taxa with the exception of the Lepidoptera possess relatively light wings and correspondingly enjoy a reduction in relative inertial resistance to body rotation. In many flying vertebrates, use of the tail facilitates the generation of aerodynamic torques and substantially enhances axial agility. Contrasting with maneuvers, stability in flight requires force and moment balances that are attained via bilateral symmetry in wingbeat kinematics. All volant animals fly using bilaterally paired appendages, whereas energetic costs of morphological and kinematic asymmetries between contralateral wings may be substantial. Geometrical constraints on wingbeat kinematics may limit force production and thus flight agility in many behavioral circumstances. Unitary limits to animal flight performance and maneuverability are unlikely, however, given varied and context-specific interactions among anatomical, biomechanical, and energetic features of design.
P3.74 DURICA, D.S.*, ANILKUMAR, G.,WU, X., HOPKINS, P.M., University of Oklahoma, Sree Narayana College, India, University of Oklahoma, University of Oklahoma A search for EcR and RXR A/B isoform gene expression during crustacean limb regeneration and oogenesis.
We have previously reported the isolation of EcR and RXR gene homologs in the fiddler crab, Uca pugilator. In insects, isoforms for both the EcR and RXR/USP proteins have been identified; these isoforms arise from the splicing of alternative A/B domains onto common C and E/F domains. Expression studies and mutant analysis strongly suggest that these isoforms have different physiological roles. Detailed analyses of the recovered crustacean clones, however, recovered an invariant A/B domain open-reading frame for each gene. Ribonuclease protection assays (RPA) were employed to obtain an appraisal of the relative ratio of the recovered A/B domain-containing transcripts to common domain UpEcR and UpRXR sequences. RPAs were conducted using limb buds corresponding to limb regeneration stages used in previous studies and were also initiated with ovaries containing oocytes at different periods of oogenesis.To compare the relative steady-state abundance of A/B domain sequences to common domain sequence, RNAs were hybridized to both A/B domain and common domain probes, and the level of protection tritrated against known amounts of full-length sense cRNAs. At several stages examined, the relative level of A/B domain sequence protected is significantly less than common domain; additional bands of lower molecular weight resulting from hybridization to the A/B domain probe are also observed. Similar results were obtained using ovarian tissue samples. The difference in the abundance of A/B containing transcripts relative to total UpEcR and UpRXR mRNA suggests that alternative processing may produce A/ B receptor isoforms in Uca, similar to the situation observed in insects. The ovary also represents another potential target tissue for ecdysteroid control.
41.3 DURIE, C. J.*, TURINGAN, R.G., Florida Institute of Technology, Melbourne. Relationship between durophagy and feeding functional design in marine fishes: intraspecific variation in ecological morphology.
The relationship between oral jaw biomechanics and consumption of hard prey was compared between populations of two perciform and five tetraodontiform species to examine intraspecific ecomorphological variation in marine fishes. Gut content analysis revealed that the magnitude of durophagy (feeding on hard-shelled invertebrates, such as crabs and sea urchins) varied between populations of each species. Difference in the relative magnitude of durophagy between populations was associated with intraspecific differences in key biomechanical properties of the prey-capture and processing mechanisms. The more durophagous populations had more massive jaw bones and muscles than conspecifics that consumed soft prey. We hypothesize that marine fishes have the ability to alter the development of their feeding mechanism to match the requirements for capturing and processing locally availabe prey-resources at postrecruitment habitats, such as coral reefs and estuaries.
65.5 DWORKIN, I.M.*, LARSEN, E.W, Univeristy of Toronto. Temporal dynamics of the interaction between homothorax and Antennapedia in D. melanogaster.
The antenna to leg transformations induced by dominant alleles of Antennapedia (Antp) have become classic examples of homeotic transformation in D. melanogaster. It has recently been suggested that this transformation is due to Antp mediated repression of the homothorax (hth) gene. Loss of hth activity from the antennal imaginal disc results in transformation to leg identity, and results of co-expression of Antp and hth have been interpreted as rescuing the antennal phenotype. While Antp activity in the antennal disc does seem to repress hth transcription, several inconsistencies have lead us to investigate the interactions between these two genes in a more quantitative manner. We have investigated how short pulses of Antp via a heat shock mediated transgene (HS-Antp) induces morphological transformations, and represses hth expression. As well, we have employed a HS-hth transgene to examine the temporal dynamics of rescue of the Antp mediated transformation. Our results indicate that there is only a weak correlation between loss of hth expression and morphological transformation. Short pulses of hth appear to be sufficient to induce partial rescue of the Antp mediated transformation. These results will be discussed in terms of the presumed roles of hth in the antennal disc.
P3.70 DZIALOWSKI, E.*, VON PLETTENBERG, D., ELMONOUFY, N., BURGGREN, W., University of North Texas, Denton, Freie Universitat, Berlin. Chronic hypoxic effects on metabolism and hematology in developing chicken embryos.
Chicken embryos were
exposed to chronic hypoxia (PO2 131 mmHg) during development, and assessed for detrimental metabolic effects and the ability to repair them. Eggs were incubated in one of four groups: untreated (i.e. 155 mmHg), or treated with continuous 15% hypoxia during days 1–6 (D1–6), 6–12 (D6–12), or 12–18 (D12–18) with normoxia during the remaining incubation. Metabolism (VO2), body mass, hemoglobin (Hb), and hematocrit (Hct) were measured in eggs on days 12 and 18 and in hatchlings. Ability to maintain VO2 was measured acutely during a step-wise decrease in PO2 from normoxia to hypoxia (55 mmHg). At day 12, VO2 from D1–6 and D6–12 populations was significantly lower than untreated eggs. Pcrit in D6–12 eggs was lower than in untreated and D1–6 eggs. Body mass of day 12 embryos in hypoxia from D6–12 was significantly lower than in untreated embryos, while Hct and Hb were higher. On day 18, D6–12 eggs had VO2 significantly lower than untreated eggs. Body masses of D6–12 and D12–18 eggs were significantly smaller than untreated eggs. Hct and Hb did not differ between treatments. In hatchlings, VO2, mass, Hb, and Hct were similar among treatments. However, D1–6 and D12–18 eggs produced hatchlings with lower Pcrits than untreated eggs or D6–12 hypoxia exposed eggs. Long term effects of hypoxia on VO2 and mass occurred in D6–12 embryos. Differences in VO2 and mass between untreated eggs and D6–12 eggs were observed on day 12 and 18, but disappeared upon hatching. Chronic hypoxic exposure during critical periods in development alters the developmental physiological trajectories and modifies the phenotypes of developing embryos.
P1.20 EADS, B. D.*, HAND, S. C., University of Colorado, Boulder, Louisiana State Univ, Baton Rouge, Dept of Biologi. Modulating mitochondrial transcription in Artemia franciscana embryos.
Gastrula stage embryos of the brine shrimp Artemia franciscana exhibit developmental and metabolic arrest in response to adverse environmental conditions such as anoxia. This arrest is coordinated and profound, indicating a high degree of control at the level of gene expression. Previous studies have shown an arrest during anoxia of protein synthesis and degradation, with concomitant extension of protein half-life, as well as decreased nuclear transcription. Mitochondria isolated from these embryos provide an ideal system in which to study mechanisms of transcriptional modulation during physiological challenge, including lack of O2 and the lowered ATP concentrations and pHi associated with anoxia. For example, mitochondrial half-life can be measured in organello in a way impossible with isolated nuclei. Using dot blots of mtRNA, mitochondria exposed to anoxia in vitro had significantly longer RNA half-lives than did aerobic mitochondria, indicating degradation is arrested by lack of oxygen. In addition, when exposed to anoxic pHi in vitro, an even greater proportion of the mtRNA was present after 6 h than in anoxic samples, demonstrating that the pH decline during anoxia is more important for halting degradation than is O2 lack per se. We tested the hypothesis that lack of ATP is a mechanism for halting RNA degradation under anoxia by adding 1 mM ATP in vitro to anoxic mitochondria and found no increase, suggesting that lack of ATP is unlikely to be a causal mechanism. We also developed a nuclease protection assay for new transcription initiation events to test whether initiation by isolated mitochondria contributes to overall transcript levels. Preliminary data indicate that this is the case, and that anoxia decreases the amount of de novo initiation.
48.1 EARLS, K.D., American Museum of Natural History. Skeletal diversity and morphology in Anseriformes: an explicitly phylogenetic analysis.
Birds are very conservative in their overall-morphology, and yet have diversified across a remarkable spectrum of locomotor behaviors. The associations of morphology with locomotor specializations have been murky, however, due to a lack of resolution within and among many avian clades. While it has been shown in other vertebrate groups that changes in bone shape and strength are often associated with locomotor transitions, this has not been clearly demonstrated for birds. To shed light on this problem, I have performed an explicitly phylogenetic analysis of bone morphology in the Anseriformes (ducks, geese) with two primary goals. First, I test the relationship between bone morphology, locomotor specialization, and phylogenetic history. Second, I evaluate the effects of competing phylogenetic hypotheses on the morphological analysis. This study is a first step toward understanding morphological changes which may have occurred early in the radiation of modern avian taxa.
19.6 EDBLOM, T.L.*, KARASOV, W.H., University of Wisconsin-Madison. Solar ultraviolet-B radiation does not affect hatching success of Rana pipiens (northern leopard frog) eggs under natural conditions along a contamination gradient.
We compared the hatching success of Rana pipiens (northern leopard frog) eggs at field sites located along a known contamination gradient in the Green Bay and Fox River ecosystem, Wisconsin, U.S.A. Our investigation was designed to determine whether there were differences in hatching success or incidence of deformities when eggs were covered with shields that transmitted different levels of UV-B. We also wanted to determine if UV-B might be acting synergistically with agents in the water to further reduce hatching success and increase incidence of deformities at the more contaminated field sites, as indexed by sediment polychlorinatd biphenyl (PCB) and heavy metal levels. One Green Bay pond and one Green Bay wetland site were relatively uncontaminated (both <0.025 mg/kg sediment PCB concentration). Another Green Bay wetland site and a Fox River site were relatively more contaminated (3.7 and 3.2 mg/kg sed. PCB conc., respectively). We found significant differences in both hatching success and incidence of deformities between sites in the field, but these differences were not attributable to UV-B. Furthermore, there was no relationship between hatching success and level of contamination. These results suggest that leopard frogs, at least at the egg (for hatching success) and early tadpole (for deformities) stages may not be sensitive to current levels of UV-B radiation even in somewhat polluted environments.
P2.6 EDSINGER-GONZALES, E.*, VAN DER ZEE, M., DICTUS, W.J.A.G., VAN DEN BIGGELAAR, J.A.M., University of Utrecht. The development of radialized and twinned gastropod embryos and its implication for spiralian development.
Establishment of the adult body plan in molluscs requires induction by the blastomere 3D during embryogenesis. To understand 3D's developmental function, we interfered with its specification in the gastropod, Tectura scutum, and examined subsequent development. By incubating embryos in brefeldin-A, a fungal toxin that rapidly and reversibly dissolves the Golgi apparatus, we can temporarily shut down cell-cell communication. Varying either the concentration of brefeldin-A or the timing of treatment resulted in 100% radialized, twinned or normal larvae. In absence of 3D, radialized embryos did not establish bilateral cleavage symmetry. Despite this, development closely followed that of control larvae as they underwent gastrulatation and differentiated adult tissues. As veligers, gastropod larvae are bilaterally symmetric with the dorsal-ventral axis at a right angle to the animal-vegetal axis. In contrast, radialized larvae maintained the quadri-radial symmetry of the embryo, with dorsal-ventral structures occuring in a radial series along the animal-vegetal axis. Twinned embryos shared an animal apical tuft and a vegetal mouth while all other structures developed in duplicate and as mirror images across the animal-vegetal axis. We propose that 3D's developmental function is limited to the establishment of bilateral symmetry. By breaking the continuity of quadriradial symmetry against a backdrop of regional determinants along the animal-vegetal axis, 3D's signal enables previously equivalent blastomeres to establish identities. The adult body plan then arises over the course of gastrulation by a process of progressive induction, the product of de novo interactions resulting from stereotypic, cell lineage-defined gastrulation movements.
69.2 EDWARDS, R., DePaul University Cultural evolution of scientific values: grant overhead in a parasite-host model.
From 1968 to 1992, basic science in the United States experienced an economic condition so pervasive and significant that it was rarely acknowledged to occur. During this period, "grant overhead," or the requested percent by which a grant budget was increased, was not limited to any specific amount, but rather was negotiated annually with no set limit.The requested amounts rapidly increased from a maximum of 20% to in some cases over 80%. Neither the necessary paperwork (e.g. Circular A-21) nor the Department of Health and Human Services were then equipped for this degree of negotiation, and by the early 1980s these monies had become an important source of operating funds for university administrations. Faculty hiring and success reflected these priorities, and the ability to generate overhead funds became a central factor of academic life. Most significantly, the administrative priorities had become internalized by faculty as values. This presents a remarkable example of cultural evolution, using funds as a marker of energy: during this period, a parasite-host system operated up to and including the modification of the host's behavior in favor of parasite vigor. I present both the mechanics and the impact of this system on ourselves as academics and scientists, including aspects of teaching, hypothesis testing, mentoring, and status. Also, Congressional hearings in 1992 have led to an important change in the system, such that administrative overhead is limited to 26%. This change is beginning to affect academia and its grant-oriented practices. I present an outline of the relevant concerns and issues.
P2.28 EDWARDS, D.D., University of Evansville. Increased fluctuating asymmetry among chironomid midges in response to ectoparasitic water mites: implications for fluctuating asymmetry theory.
The larvae of most species of water mites must undergo a brief parasitic phase with insects to complete their life cycle. Several studies have found a significant correlation between mite load and the degree of fluctuating-asymmetry (FA) host characters, suggesting that mites increase FA through their effect on developmental stability. To date, FA primarily has been reported among hemimetabolous insects that become infested during pupal ontogeny. Holometabolous insects that are parasitized by mites when they are adults are not expected to exhibit FA because they are infested once they have completed development. Parasitic associations between the water mite Unionicola foili and the holometabolous midge Chironomus tentans were established in the laboratory and revealed that FA of forewing length was significantly greater in infected than in uninfected midges. These results are inconsistent with the initial prediction, suggesting there are other mechanisms by which larval mites may affect FA of host midges. Behavioral observations revealed that the presence of mite larvae induced an increase in antiparasitic behavior by pupal C. tentans. Because antiparasitic behavior id assumed to be extremely time consuming and energetically expensive, it may be expected to have an affect on the developmental stability of midges and thus increase the degree of FA.
18.3 EDWARDS, D. R.*, WOODIN, S.A., University of South Carolina, Columbia. Should worms of a feather stink together? The effects of prey density and aggregation on predator deterrence.
Halogenated hydrocarbons are widespread among hemichordates and polychaetes in temperate sedimentary environments. The bromophenols produced by some larger (>3cm in length) macroinfauna act as predator deterrents. However, many of the infaunal organohaline producers are small (<1cm in length), especially in relation to the bite size of their common predators. The ability of these small organisms to deter predators may be dependent not only on the production of deterrent compounds by individuals, but on the structure of the surrounding community. In this study, we examine whether patches of small individuals with such compounds are less palatable to infaunal predators than patches of individuals without, and whether deterrence is dependent on prey density. Spot ( Leiostomus xanthurus), mummichogs (Fundulus heteroclitus) and grass shrimp (Paleomonetes sp.) were offered patches of small (1–2 mm3) cubes of surimi with and without bromophenols. The cubes were offered at a high density (100 cubes/0.01 m2), low density (30 cubes/0.01 m2), and an aggregated low density (30 cubes divided into 6 1cm2 patches). Results of these choice experiments demonstrate that, at least for some predators, bromophenols are effective predator deterrents for small prey, and that this effect increases with density and aggregation.
S5.1 EHLERINGER, J.*, CERLING,T., University of Utah. Possible relationships between atmospheric carbon dioxide and mammalian grazers.
We explore the possible relationships between photosynthetic pathway, changing atmospheric carbon dioxide, and mammalian herbivores. Atmospheric carbon dioxide levels have changed over the last 200 million years; the recent pattern of increasing anthropogenic emissions has resulted in a dramatic increase in atmospheric carbon dioxide today that differs from atmospheric carbon dioxide in the glacial-interglacial cycles of the past. At the same time, many questions remain unanswered about abrupt changes in mammalian diversity. Might the observed changes in atmospheric carbon dioxide and changes in mammalian diversity be related through photosynthetic pathway differences that occur as a function of environmental conditions? Modeling efforts predict shifts in C3/C4 plant abundance in response to changes in atmospheric carbon dioxide. Our objectives are to better understand the constraints that atmospheric carbon dioxide places on ecosystem productivity, which may in turn influence mammalian grazers.
26.4 EIDIETIS, L.*, WEBB, P. W., FORRESTER, T.L., University of Michigan, Ann Arbor. The abilities of two morphologically different fishes to counteract rolling disturbances.
We increased rolling moments and decreased negative metacentric heights of spiny rayed Lepomis macrochirus (bluegill) and soft rayed Semotilus atromaculotus (creek chub) by attaching weights and floats which, together, were neutrally buoyant. Weight and buoyant force were normalized by fish mass, and moment arms and metacentric heights by volume-1/3. Fish behavioral responses used to counteract the disturbance were observed in conditions that restricted swimming and in conditions that allowed free swimming. Threshold responses were defined when a disturbance first caused fish to roll 90f (the limit of initial stability) and when fish were not able to right themselves (the limit of ultimate stability). When swimming was restricted, initial stability was greater for chub than bluegill. When conditions allowed free swimming, initial stability was similar for both species. Ultimate stability was similar for both species irrespective of whether swimming was restricted.
P3.55 ELF, P.K.*, FIVIZZANI, A.J., University of North Dakota. Changes in sex steroid levels in the yolks of the Leghorn chicken, ( Gallus domesticus), during embryonic development.
We have hypothesized that yolk hormones play a role in sexual differentiation in species with temperature-dependent sex determination (TSD), in which incubation temperature determines the sex of the offspring. To compare possible differences in yolk hormone patterns between TSD animals and those with genetic sex determination (GSD), a series of experiments have been initiated using the Leghorn chicken, Gallus domesticus. The chicken was chosen for this study because its sexual differentiation has been well characterized. The purpose of these investigations was to determine changes in the levels of androstenedione (A), dihydrotestosterone (DHT), estradiol (E) and testosterone (T) in the yolks of chicken eggs during embryonic development. Eggs were collected, labeled for clutch and egg number, and incubated at 37.8°C. Eggs were sacrificed at predetermined times during development, embryos staged and yolk material collected. Yolks were homogenized and hormones extracted. A, DHT, E and T were separated via column chromatography and hormones measured using RIAs. Results show decreases in the levels of both A and T during embryogenesis, similar to those we reported in the alligator, with A levels being significantly greater initially than those of all other hormones. DHT levels mirrored those of T. Chicken E levels however, differed from those we measured in both the turtle and the alligator. E levels were less than T throughout most of development, and though they do decline slightly, E levels in yolks of chicken eggs show a significant increase between embryonic stages 40 and 45.
P2.65 ELLERBY, D. J.*, SPIERTS, I.L.Y., ALTRINGHAM, J. D., University of Leeds, Niels Stensen Foundation. Fast muscle function in the European eel ( Anguilla anguilla, L.) during aquatic and terrestrial locomotion.
Eels are capable both of locomotion in water and on land using undulations of the body axis, powered by the lateral musculature. Differences in kinematics and the underlying patterns of fast muscle activation are apparent between locomotion in these two environments. Fast muscle power outputs were measured using the work loop technique, under conditions that simulated their use during aquatic and terrestrial locomotion. The muscle strain and stimulation parameters associated with swimming generated greater force and power than those associated with terrestrial crawling. This decrease in muscle performance may occur because on land the eel is constrained to a particular kinematic pattern in order to produce thrust against an underlying substrate. Muscle properties changed along the body axis as reported in other teleost fish. Maximum power outputs using optimal strain and stimulation parameters were 17.3 ± 1.3 Wkg–1 in muscle from 0.45 BL (body lengths from the snout) and 16.3 ± 1.5 Wkg–1 in muscle from 0.75 BL. Time from stimulus to peak force Ta was 82 ± 6 ms at 0.45 BL and 93 ± 3 ms at 0.75 BL. Time from stimulus to 90 % relaxation T90 was 190 ± 13 ms at 0.45 BL and 228 ± 11 ms at 0.75 BL.
26.3 ELLERBY, D. J.*, SPIERTS, I.S. Y., ALTRINGHAM, J. D., University of Leeds, Niels Stensen Foundation. Slow muscle power output of yellow- and silver-phase European eels ( Anguilla anguilla, L.): changes in muscle performance prior to migration.
The European eel ( Anguilla anguilla, L.) has a complex life cycle involving a lengthy spawning migration. The differences in the locomotory demands on different life history stages are considerable. Eels swim in the anguilliform mode in which muscle function has been assumed to be relatively uniform along the body axis relative to other teleosts. The work loop technique was used to determine slow muscle power outputs in yellow (non-migratory) and silver (migratory) life history phases. Swimming kinematics of the two phases were also measured for comparison. Maximum slow muscle power outputs under approximated in vivo conditions were 0.24 Wkg–1 in yellow-phase eel and 0.74 Wkg–1 in silver-phase eel. Power output peaked at cycle frequencies of 0.23 to 0.8 Hz. Muscle activation (Ta) and relaxation (T90) times were greater in yellow- than in silverphase eels. Differences in swimming kinematics and the frequency distribution of tailbeat frequency at a swimming speed of 0.40 BLs–1 suggested differences in underlying patterns of muscle recruitment between the two life history phases.
P2.42 ERNST, H.H.*, RICHARDSON, J. F., SATTERLIE, R.A., Arizona State University. Morphological changes in an asymmetric neuron of the right pleural ganglion in the sexually mature vs. immature pteropod mollusk.
One of the largest neuron somata of the right pleural ganglion of Clione limacina belongs to a cell that does not have a homologue in the left pleural ganglion. In the immature animal, the soma is around 50um in diameter and appears translucent with substage illumination. In the mature animal, the soma is around 80um in diameter and appears opaque. With illumination from above, the cell is white in color. Light and electron microscopical examination of both immature and mature "Pleural White Cells" indicate the presence of numerous, large densecored vesicles in the cytoplasm of the mature animals, but not in the immatures. In addition, several smaller pleural neurons appear light opaque in mature animals. The appearance of the white color in the smaller neurons, but not in the Pleural White Cell, is coincident with immunoreactivity of small neurons to an antibody to Aplysia egglaying hormone. Similarly, immunoreactive somata, to an Aplysia sensorin antibody, which is believed to specifically label primary mechanosensory neurons, is found in the right, but not the left pleural ganglion of sexually mature animals. Again, only small neurons are labelled. Thus significant morphological changes, and presumed physiological changes, occur in the right pleural ganglion of Clione when it develops sexual maturity.
S10.4 ESCH, G., BARGER, M., FELLIS, J., Wake Forest University. Transmission of parasitic helminths: style, elegance, complexity.
Traditionally, the field of parasitology has dealt with eukaryotic animals, to the exclusion of viruses, bacteria, fungi, etc., which is the way we will approach our presentation. Our focus will be on certain ecological aspects of the life cycles and life-history strategies employed by digenetic trematodes, a diverse group of platyhelminths that includes some 25,000 described species. More specifically, our interests rest with the nature of host/parasite interactions within molluscan intermediate hosts and the manner in which these interactions, or lack thereof, function in structuring trematode infracommunities within these molluscan intermediate hosts. Literature in this area suggests that predation/competition may be a significant structuring force for infracommunities in certain marine prosobranchs, but not others, and that temporal/spatial factors may be involved as structuring forces in at least some freshwater pulmonates. These, and other, issues will be discussed.
67.3 ESPINOZA, N.R., Louisiana State University, Baton Rouge. Effects of developmental temperature on musculoskeletal growth and jumping performance in the treefrog Hyla chrysoscelis.
Several vertebrate species have shown ontogenetic adjustments in the form and material properties of the growing musculoskeletal system to allow the same level of locomotor performance in juveniles and adults. The rate of growth and amount of time the musculoskeletal system has to develop may affect the amount of compensatory change needed to produce the same level of performance; for example, the faster the growth rate and/or the shorter the amount of time for development, the greater the need for these adjustments. To test these predictions, individuals of Hyla chrysoscelis were raised at 28fC and 18fC to evaluate the effects of developmental duration and growth rate on bone and muscle morphology, bone material properties, and jumping performance. Although two-fold differences in developmental duration and larval growth rates were found between frogs raised at 28fC and 18fC, little or no difference was found in hind limb morphology, bone shape, bone mineral content, bone material properties, relative muscle mass or jumping performance at the end of metamorphosis. However, during the first nine weeks of post-metamorphic growth in both groups, absolute jumping performance, relative proportion of hind limb muscle mass, and bone material properties changed with age. These results suggest that an increase in the relative proportion of hind limb muscle mass, as well as an increase in the strength and stiffness of the hind limb skeleton, contribute to the improvement of jumping performance during post-metamorphic growth. Supported by a Howard Hughes Predoctoral Fellowship and NSF (IBN-9701121).
P2.77 ESSNER, R.L., Ohio University, Athens. Comparison of takeoff kinematics in gliding and nongliding squirrels.
Precise descriptions of behavior are key to understanding the role of morphology in the evolution of novel locomotor modes. While a number of studies have compared morphological variation among gliding and nongliding forms, there is currently a lack of insight into the extent of variation among locomotor behaviors. This has led to questions concerning the degree of specialization necessary for gliding versus nongliding (leaping) locomotion. In order to address this concern I examined takeoff kinematics in a gliding arboreal sciurid ( Glaucomys volans) and two nongliding relatives ( Tamiasciurus hudsonicus, Tamias striatus). Animals were filmed launching from a 1.5-meter horizontal platform with high-speed video at 240 frames/second in lateral and dorsal views. Landmarks were digitized on the limbs, tail, and body and converted into 3D coordinates. Locomotor behavior was examined by generating kinematic profiles of angular motion at the limb joints and tail. Comparisons among the three taxa revealed similarities in the majority of kinematic parameters, indicating that takeoff behavior in these arboreal rodents is relatively conservative. Furthermore, the presumed evolutionary transition from leaping to gliding likely did not involve substantial changes related to the takeoff phase of locomotion.
P1.26 ESTES, A.M.*, KEMPF, S.C., HENRY, R.P., Auburn University. Carbonic anhydrase induction by zooxanthellae in Cassiopea xamachana.
Endosymbiotic dinoflagellates of cnidarians are encased in multiple membranes, causing difficulty in acquiring inorganic carbon for photosynthesis. Host carbonic anhydrase(CA), which catalyses the reversible dehydration of HCO3-, can supply endosymbionts with unlimited CO2 by accessing the large HCO3- pool in seawater. Bell tissue from Cassiopea xamachana, was examined to determine if the localization and induction of CA activity were correlated with the density and location of zooxanthellae. Symbiotic and regenerated recolonized C.xamachana bell tissue had 5 times and 1.7 times, respectively, greater CA activity than aposymbiotic native and regenerated tissue. Symbiotic native and recolonized tissue contained respectively, 3 and 6 fold greater algal populations than aposymbiotic tissues. The oral epithelial layer, which receives more intense sunlight, had 1.2 greater CA activity and 5 times the algae than aboral. CA localized using the fluorescent inhibitor 5-dimethylaminonapthalene-1-sulfonamide (DNSA), revealed symbiotic and oral epithelial tissues 1.5 times brighter than aposymbiotic and aboral tissues. CA activity and algal density in symbiotic and aposymbiotic animals were highest at the bell edge and lowest near the manubrium. Thus, the postion and density of algal populations are positively correlated with CA concentration and location. Symbiotic C. xamachana incubated in the Photosystem I inhibitor, 3-(3,4 dichlorophenyl)-1,1-dimethylurea (DCMU)showed a 1.7 fold decrease in CA activity after five days. Thus, not only algal density, but also photosynthetic rate determines CA concentration.
S10.10 FAETH, S.H., Arizona State University, Tempe. Fungal endophytes and host plant symbioses: mutualism, neutralism, or antagonism?
Systemic endophytic fungi are thought to interact mutualistically with their host grasses mainly by increasing resistance to herbivores via alkaloids, as well as by increasing drought resistance, germination success, competitive abilities and deterring seed pathogens and predators. However, antiherbivore effects have been documented only for a relatively few grasses, mostly agronomic ones, and mostly on non-native herbivores. There are few studies of the interaction of endophytes in native grass populations and communities. I show that relatively few native grasses infected with systemic endophytes have strong negative effects on either invertebrate or vertebrate herbivores. Observational and experimental studies of Neotyphodium-infected Arizona fescue, a widespread and native grass, demonstrate a general lack of herbivore resistance. In field and greenhouse experiments, infected seeds show reduced germination success and increased susceptibility to fungal pathogens. The only positive effects of the endophyte appear to involve increased rates of plant growth, but only under specific environmental conditions and only with certain plant genotypes. I propose that the mutualism between endophytes and host grasses is conditional based upon plant and fungal genotype, which influence alkaloid production, and environmental factors.
S6.4 FARMER, C.G., University of Utah, Salt Lake City. Myocardial oxygenation and the evolution of the vertebrate cardiopulmonary system.
For many vertebrates, there are no other normal stresses to which the cardiopulmonary system is exposed that come close to the extreme stresses of heavy exercise. Hence it is expected that the demands of exercise have exerted strong selection pressures on the evolution of vertebrate cardiopulmonary system. I have been examining the importance of air-breathing during exercise in several fishes as a potential mechanism of myocardial oxygenation. Similarly, I have been investigating the importance of the intracardiac shunt of reptiles in myocardial oxygenation during exercise. This research has employed a variety of techniques (ECG, blood gas, blood pressure, and blood flow measurements). Although preliminary, my findings suggest that myocardial oxygenation is not adequate in some air-breathing fishes when exercising in well oxygenated water but denied access to air. Furthermore, when the potential benefits to myocardial oxygenation of the intracardiac shunt are removed by exercising turtles under hypoxic conditions, cardiac function is perturbed. Hence, the necessity of an adequate supply of oxygen to the heart during activity may have influenced the evolution of the vertebrate lung and the intracardiac shunt.
P3.72 FASANO, C.*, QUACKEN-BUSH, L.S., University North Carolina, Wilmington. Growth of juvenile blue crabs, Callinectes sapidus.
In North Carolina's Cape Fear River estuary, juvenile blue crabs are often found in sand and mud habitats far beyond the mouth of the estuary. Predators, prey availability or other factors, may drive the crabs' invasion of the low salinity portions of the estuary. We also expected that there would be consequences on the growth rates of these juvenile blue crabs. We collected small (8–22 mm) juvenile crabs at the mouth of the estuary and monitored their growth over several molt cycles in a controlled lab environment. The smallest blue crabs had the largest growth rates, these rates slowed as the crabs increased in size. Crabs growing at three different salinities had about equal growth rates, and equal molt cycle durations, but significant differences in the number of molts completed. It appears that low salinity areas are suitable for rapid crab growth, when other factors are controlled. Supported by the CRUI program grant : DBI: 99-78613 from the National Science Foundation.
7.5 FAUCHALD, K., Smithsonian Institution. Distribution of scales in polynoid scaleworms (Annelida, Polychaeta).
Polynoids have some of the dorsal cirri replaced by flattened scales (elytrae) more or less covering the body. An overview of the type species of most genera of the family demonstrated a few interesting patterns. Species with less than 12 pairs of elytrae all have less than 30 segments and are found in deep water, either pelagically or associated with hot vents. These taxa appear to belong to several different clades. The first 12 pair of elytrae are always on segments 2, 4, 5, 7, 9, 11, 13, 15, 17, 19, 21 and 23. The next three pairs of elytrae are usually either on segments 25, 27 and 29 or on segments 26, 29 and 32; the latter is by far the most frequent and a very large number of polynoid taxa have 15 pairs of elytrae with this distribution. Most taxa with 15 pairs of elytrae consist of less than 40–45 segments; but a few long-bodied taxa with as many as 100 segments lack elytrae on the posterior half of the body. When more than 15 pairs of elytrae are present, the distribution on segments 30–45 is often irregular and variable, except in taxa with 18 pairs of elytrae in which patterns corresponding either to the 25, 27, 29 or the 26, 29, 32 patterns are present. In long-bodied taxa with 50 or more segments, the distribution stabilizes in most taxa into two patterns with the elytrae present on either every second or every third segment, corresponding to the patterns seen on segments 24–32. In many species the two last pairs of elytrae are on consecutive segments no matter what the previous distribution were. The distribution of the elytrae correlates better with the numbers of segments present than with the length of the specimens. Short-bodied taxa appear to have evolved at least twice within the family, assuming that the long-bodied condition is plesiomorphic.
S15.10 FEDAK, M.*, LOVELL, P., MCCONNELL, B., HUNTER, C., University of St Andrews. Methods for overcoming the constraints of long range telemetry of biological information from animals: getting more useful data from small packages.
Many species carry out their most interesting activities where they can not be observed or monitored. Marine mammals are perhaps extreme in this group, accomplishing their most astounding activities both distant from land and deep in the sea. Collection, storage and transmission of data about these activities are constrained by the energy requirements and size of the recording loggers and transmitters. The more bits of information collected, stored and transmitted, the more battery is required and the larger the tag must be. We therefore need to be selective about the information we collect, while maintaining detail and fidelity. To accomplish this in the study of marine mammals, we have designed "intelligent" data logger/transmitters that provide contextdriven data compression, data relay, and automated data base storage. We later combine these data with remotely sensed environmental information and other oceanographic data sets to recreate the environmental context for the animal's activity, and we display the combined data using computer animation techniques. In this way, the system can provide near real time "observation" of animal behaviour and physiology from the remotest parts on the globe. To illustrate the approach, we will present examples of its use in southern elephant seals and beluga whales from the polar seas.
S5 FEDER, M.E., University of Chicago. Plant and animal comparative physiology/ biochemistry, evolutionary physiology, ecological physiology, and physiological ecology: opportunities for synergy.
Both the communities of plant biology researchers and animal biology researchers include multidisciplinary groups that combine physiology, ecology, biochemistry, biomechanics, and evolution, but historically these groups have often been as distinct as the organisms they study. This symposium will challenge this historic distinction by asking in what ways the study of plant and animal function in environmental/evolutionary context need be separate disciplines, what biological issues transcend the two communities, and how best can plant and animal biologists realize the synergies afforded by their complementary viewpoints and study organisms? To do this, the symposium will partner distinguished plant and animal biologists to discuss topics of mutual interest: global climate change; sensing, signalling, and responding to the environment; mechanisms and implications of dormancy; and behavior versus tolerance as alternative responses to environmental stress.
S13.7 FENCL, H.S., University of Wisconsin System. Reaching all students: supporting diversity in a science classroom.
This session will explore both the importance of, and resources for, teaching a diverse group of students. Athough the emphasis of the discussion will be on genderconscious teaching, many of the issues raised are equally important to minority students and those from a spectrum of socioeconomic backgrounds. Ideas and resources for curricular reform—of a single course or across the major—will be presented. Experiences of educators at the UWS Women & Science Curriculum Reform Institute will be used as illustrations.
P3.93 FENTRESS, J. A.*, BROUWER, T.H., BROUWER, M., MCLACHLAN, J. A., CHEEK, A.O., Southeastern Louisiana University, Hammond, University of Southern Mississippi, Ocean Springs, University of Southern Mississippi, Ocean Springs, Tulane University, New Orleans, LA, Southeastern Louisiana University, Hammond. Examination of a potential environmental antiestrogen.
Anthracene, a polyaromatic hydrocarbon, has been shown to induce anti-estrogenic effects in fish. In the medaka, Oryzias latipes, short term exposure to 12 or 20ug/ml anthracene (ANT) blocks estrogen induced feminization, while long term exposure leads to reduced fertility and hatching success. To determine if anthracene is an estrogen receptor antagonist, we measured vitellogenin (VTG) production in response to estradiol (E2) +/– anthracene. VTG serves as a natural reporter gene for estrogen receptor activation. We exposed fry for 2 or 8 weeks post hatch to one of the following treatments: water, solvent, 1 nM E2, 12 ug/ml ANT, 20 ug/ml ANT, 1nM E2 + 12 ug/ml ANT, or 1nM E2 + 20 ug/ml ANT. Fish were sub-sampled at 2, 4, and 8 weeks post hatch for VTG analysis. Vitellogenin was analyzed using Western blots and quantified by densitometry. Fry exposed to estrogen for 2 weeks and sampled at 2 weeks produced VTG, while fish sampled at 4 and 8 weeks showed an attenuated response to estrogen. Fish exposed to estrogen for 8 weeks produced VTG throughout the exposure period. When exposed to ANT alone fish did not produce VTG. Regardless of dose or exposure duration, ANT did not prevent the production of vitellogenin in co-exposed fish. Because anthracene was unable to block the production of vitellogenin, it is unlikely that its antiestrogenic effects are mediated through the E2 receptor.
S6.10 FERRY-GRAHAM, L.A.*, WAINWRIGHT, P.C., University of California Davis, University of California Davis of California Davis. Using functional morphology to test general ecological theory.
Even before Hutchinson defined what he coined the ëfundamental nicheí, researchers have been striving to understand what it is that makes species different, and what allows them to survive in the time and space that they do. Since that time, many theories have been advanced which encompass an array of ecological, evolutionary, mathematical, and simply logical principles. The goal has been to develop ecological theories that can, among other things, make specific and robust predictions about how and where organisms should live. An often underestimated or unexplored parameter of these models is the role of the organismsí functional morphology. A more complete understanding of how the features of an organismís anatomy work to allow the organism to accomplish certain tasks has allowed us to revisit-some of these models from an enlightened perspective. We use kinematic studies of prey capture in several types of fishes as model systems to generate and test predictions related to diet specialization and breadth. These include, but are not necessarily limited to, predictions regarding why an organism might specialize, and the potential ecological and evolutionary consequences of specialization. We also consider several definitions of specialization and attempt to align these based upon shared ecological and evolutionary principles. We note that not all functional morphological systems are ideal for testing ecological models, as many ecological models depend on other levels of organismal design for predicting community patterns (i.e., behavior or sensory biology). We attempt to identify and define the characteristics of those certain functional morphological systems that make them useful for testing general ecological models and lead to robust predictions.
S3.11 FETCHO, J.R., SUNY at Stony Brook. New approaches to the function of neuronal circuits that might simplify (a little) studies of the evolution of behavior.
Understanding motor patterns (electromyograms) and their evolution requires understanding the neuronal circuits that produce them and the evolutionary changes in those circuits. This is not easy, which is perhaps why there are not many explicitly comparative studies of the functional organization of motor circuits for feeding or other vertebrate behaviors. Simply identifying which neurons are involved in a particular behavior in even one species is a challenge and doing this in a comparative way has been unrealistic. The problem is even more complicated because over the last decade neurobiological studies have shown how plastic the nervous system really is. Changes in motor output, even within a single animal, can occur in many ways, including changes in synaptic connections, alterations in ion channel expression in neurons, or a restructuring of the function of neuronal circuits by neuromodulators. The challenge is to develop techniques that are easily applicable across species which allow one to identify the active neurons in a behavior and to test their function. Such approaches would then allow for comparative studies of motor circuits in animals with differing motor patterns. We have been applying optical methods and fluorescent indicators to image which neurons are active during behavior of larval fish and to reconstruct their morphology in the live animal. In addition, we have developed approaches to laser kill neurons to test their function in vivo. These approaches, combined with powerful new genetic tools for fluorescently labeling neurons, should allow a more ready attack on the problems of exactly what the motor circuitry is for behaviors such as feeding and how it has changed in conjunction with the evolution of new motor patterns.
49.4 FILORAMO, N.I.*, SCHWENK, K., University of Connecticut. Ultrastructure of the lingual surface in anguimorph lizards and snakes: evolutionary and functional implications.
In squamates, one of the tongue's roles is to collect chemicals from the environment. Both volatile and non-volatile chemicals are delivered to the vomeronasal chemosensory organs (VNOs). The information gained from these chemicals allows squamates to find and identify mates and prey items. Given the tongue's central role in delivering chemicals to the VNOs, understanding the surface topology of the tongue and how it might affect the tongue's ability to retrieve environmental chemicals and deliver them to the VNOs is of high import. This study focuses on anguimorph lizards and snakes, whose tongues have become highly modified for their role in chemoreception. Snakes are widely believed to have evolved from within the Anguimorpha. Both scanning and transmission electron microscopy where employed. The surface topology of the forked region of the tongue (the tines) differs from that of posterior, unforked region of the tongue in all specimens investigated to date. The surface topology of the tines in snakes differs significantly from those of anguimorph lizards. In snakes, the tine surfaces are covered with microfacets. However, in most anguimorph lizards both the dorsal and ventral surfaces are covered depressions and the ventral surfaces have scattered small or "incipient" microfacets. Helodermatids are an exception in that instead of scattered incipient microfacets on the ventral surfaces of the tines there are clusters of larger, snakelike, microfacets. Ultrastructural features suggest that the deeply forked tongues of snakes and varanids were derived independently. Biomechanical evidence suggests that ultrastructural differences may be unrelated to function.
P1.57 FINKLER, M.S.*, SUGALSKI, M.T., CLAUSSEN, D. L., Indiana University Kokomo, New England College, Henniker, NH, Miami University, Oxford, OH. Sex-related differences in locomotor performance and metabolism in breeding spotted salamanders ( Ambystoma maculatum).
We investigated differences in metabolism and locomotor performance of male and female spotted salamanders collected during the breeding season. Male salamanders had faster voluntary crawling speeds than did females (both gravid and non-gravid). Burst swimming velocity was higher in males than in gravid females, but there was no difference in burst crawling speeds between the sexes. Oxygen consumption was greater in females both during rest and during locomotion at the voluntary crawling speed of gravid females. Both male and nongravid females sustained locomotion longer than did gravid females. These findings suggest differences in locomotor performance and energetics that may account for observed differences in arrival times at breeding sites and survival between male and female mole salamanders.
60.3 FISH, F. E., FRAPPELL, P. B., BAUDINETTE, R.V., MACFARLANE, P.M., West Chester University, La Trobe University, Melbourne, University of Adelaide, La Trobe University, Melbourne. Energetics of terrestrial locomotion of the platypus: metabolic inefficiencies due to aquatic adaptation.
The platypus Ornithorhynchus anatinus displays specializations in its limb structure for swimming which could negatively impact its terrestrial locomotion. Platypuses locomoted on a treadmill at speeds from 0.19 to 1.08 m/s.Video records were used for gait analysis and the metabolism of terrestrial locomotion was studied by measurement of oxygen consumption. Platypuses used walking gaits (duty factor < 0.50) with a sprawled stance. To limit interference from the extensive webbing on the forefeet, the platypuses walked on their knuckles. Metabolic rate increased linearly over a 2.4-fold range with increasing walking speed in manner similar with terrestrial mammals, but was low due to the relatively low standard metabolism of the monotreme. The cost of transport decreased with increasing speed to a minimum of 0.71 J/N m. When compared to the cost of transport for swimming, the metabolic cost for walking was 1.89 times greater. This difference means that the platypus pays a price in terrestrial locomotion by being more aquatically adapted than other semiaquatic or terrestrial mammals.
S11.1 FISH, F.E., West Chester University, PA. Mechanisms for enhanced maneuverability in organisms of varying flexibility.
Maneuverability with respect to turning is critical to the performance of fast swimming animals. Turning is effected by dynamic forces. For many aquatic animals, these forces are dominated by steady non-inertial forces including lift and drag. Animals can use an asymmetrically applied drag to rotate and turn. Appendages modified as paddles can produce this effect which works well in conditions dictated by low velocity, continuous turning and precise control, but incurs a high energy cost. Lift-based maneuvering systems have the advantage of producing a centripetal force to effect turning without incurring a large decelerating drag, but are limited in duration. Animals that use drag-based turning possess rigid bodies with a high degree of stability. Lift-based turning is associated with a flexible body or enlarged control surfaces. Flexible bodies possessed by fish and marine mammals have been shown to permit high levels of performance with respect to turning rate, centripetal acceleration, and turn radius. Rigid bodies do constrain turning performance, however, the inability to bend can be compensated for by the use of appendages and vectored thrust mechanisms.
64.3 FISHER, G.R.*, DIMOCK, R.V. Jr., Wake Forest University. The role of the larval mantle cells during metamorphosis of Utterbackia imbecillis (Bivalvia: Unionidae).
Larvae of Utterbackia imbecillis undergo a period of metamorphosis to the juvenile while parasitic on a host fish, but can also be induced to metamorphose in a modified cell culture medium. This metamorphosis involves some dramatic changes in the structure of the larval mantle cells which are thought to be involved in digesting the degenerating larval adductor muscle and the host fish tissue. Transmission electron microscopy and histochemistry for digestive enzymes were used to investigate the role of these cells in both fish-reared and in vitro-reared animals. TEM analysis revealed endocytosis in the larval mantle cells but not in any other larval tissues. This was true even for in vitro-reared animals which presumably ingest the larval adductor muscle since there is no fish tissue present. Fish-reared larvae showed no acid phosphatase activity; however, the larval mantle cells of in vitro-reared larvae possessed lysosomes containing acid phosphatase and were also releasing acid phosphatase into the extracellular environment at cell boundaries. The differences in acid phosphatase activity between the two rearing conditions may be due to the presence of glycogen in the fish-reared animals. Prior to the onset of metamorphosis, larvae possess large amount of glycogen stores in the tissues. In the in vitro-reared animals, these stores are depleted very early in metamorphosis, while in fish-reared animals they remain until much later. Perhaps the acid phosphatase is not activated until the cells have used up their glycogen reserves and require an external source of nutrition. It appears that the larval mantle cells play a role in the digestion of both the larval adductor muscle and host fish tissue during metamorphosis.
33.1 FOLK, D. F.*, BRADLEY, T.J., University of California, Irvine. How does selection for desiccation resistance affect the distribution of water in Drosophila melanogaster?
We are conducting experiments with five populations of Drosophila melanogaster, which have undergone laboratory selection for increased desiccation resistance for over 200 generations. For each population of desiccation-resistant flies (D flies), a control population (C flies) was maintained under identical conditions, except that C flies had ad libitum access to water. Previous studies have demonstrated that increase in desiccation resistance in D flies is associated with increases in bulk water content and reduction in cuticular permeability to water. We tested two hypotheses concerning acquisition and storage of bulk water in the desiccation-tolerant populations: (1) that reduction in post-eclosion diuresis in the D flies allows flies to accumulate more water early in the adult phase and (2) that the greatest portion of surplus water is stored in the hemolymph. Our results indicate that rate of urine elimination up to 4 h post-eclosion was not differentiated between the D flies and their controls. Differences in post-eclosion diuresis have, therefore, not evolved during selection for increased desiccation resistance. Analysis of water distribution in the body of the flies demonstratedthat the D flies have a statistically significant, 3.4-fold increase in hemolymph volume. On average 89% of the extra bulk water in the D flies is stored in the hemolymph. We are currently examining the significance of the extracellular location of this water on mechanisms of water use during desiccation in fruit flies. Funded by NSF Grant IBN9723404.
S4.7 FORWARD, R.B., Duke University Marine Laboratory. Ontogentic changes in crustacean larval behavior: contributions to transport and metamorphosis.
Larval development of many estuarine decapod crustaceans occurs in coastal/oceanic areas. Thus, larvae are transported seaward from estuaries for development and then shoreward and up-estuaries to nursery areas as post-larvae. This paper will focus on selective tidal stream transport (STST) as the mechanism for horizontal movement in estuarine areas. The behavior underlying STST varies with species and is based on either a biological rhythm in activity or behavioral responses to environmental factors associated with tides. Transport of post-larvae terminates upon settlement and metamorphosis in nursery areas. Both positive (e.g. odor from conspecifics and aquatic vegetation) and negative (e.g. ammonium, hypoxia, predator odor) cues for habitat selection and metamorphosis will be considered.
37.3 FOUGEROLLE, M.F.*,TURINGAN, R.G, Florida Institute of Technology, Melbourne, Florida Institute of Technology, Melbourne. The effects of prey type on the feeding biomechanics of Archosargus probatocephalus.
Ubiquitous species in heterogeneous, coastal habitats typically encounter variable prey-resources. The biomechanical basis for the ability of A. probatocephalus to consume both soft and hard prey organisms within its environment was examined in an attempt to understand the mechanisms that underlie the abundance and distribution of this species. Fish from the same location within the Indian River Lagoon were reared under two diets: whole bean clams ( Donax gouldii) [hard prey] and D. gouldii with shells removed (soft prey). At the end of a 70-day rearing period, fish were measured for key biomechanical features of the prey-capture and processing mechanism. Analysis of Covariance revealed that biting muscles and bones of fish fed hard prey were more massive than fish fed soft prey. For a given body size, estimated biting strength of fish reared in hard-prey diet was greater than fish reared in soft-prey diet. Total body mass and mechanical advantage of the feeding mechanism did not differ between diet treatments. We hypothesize that the ability of A. probatocephalus to consume different prey organisms is associated with its ability to alter the development of its feeding mechanism. Phenotypic plasticity appears to be one of the mechanisms that underlie a species ability to exploit locally available prey-resource.
P1.14 FOURNIER, F.*, KARASOV, W.H., MEYER, M.W., University Laval, University Wisconsin-Madison, Wisconsin DNR. The effect of feather development on the pharmacokinetics and oral bioavailability of methylmercury in common loon chicks.
Mercury is known to preferentially bind to structures containing sulfhydryl groups (e.g. keratin in growing feathers), and the latter affinity may influence the accumulation and excretion of ingested mercury in growing birds. We therefore determined the effect of feather growth on the pharmacokinetics and oral bioavailability of methylmercury in common loon chicks ( Gavia immer) as part of an ongoing research project aimed at elucidating the ecological risk of mercury to loons. Oral bioavailability was determined by comparing the blood concentration through time after oral (500 MICROg/kg body mass) and intravascular (IV; 200 MICROg/kg body mass) administration at two ages (35 and 84 days) during postnatal development (during and after feather growth). The area under the blood concentration-time curves extrapolated to infinity (AUC) were calculated from the orally and IV-dosed chicks using the trapezoidal method. Bioavailability was estimated as the ratio of the dose-corrected oral AUC to the IV AUC. Bioavailability differed between ages and it was 77% at age 35 days and 92% for 84 day old chicks. We determined pharmacokinetic parameters by fitting a two-compartment non-linear regression model to both concentration-time data sets, and this resulted in models that accurately predicted the initial rapid distribution phase and the linear excretion phase for both data sets (r2 > 0.9 in all cases). The excretion rate constant differed between ages and was found to be 0.006 and 0.048 day–1 for chicks aged 35 and 84 days, respectively. The mean elimination half-life of methylmercury in loon chicks was determined as 14 and 116 days for chicks aged 35 and 84 days, respectively. These results suggest that growing feathers are an important excretory route for ingested mercury.
P2.24 FOWLER, E.*, HILL, P.S.M., University of Tulsa, OK, University of Tulsa, OK. Individual identification of the prairie mole cricket, Gryllotalpa major.
Gryllotalpa major, the prairie mole cricket, is a rare species native to the Oklahoma grasslands. Little is known about this particular species, and information is difficult to obtain because of its subterranean lifestyle. Of particular concern is our not being able to mark individuals in a population to track movements or gauge individual mating success. This study was designed to distinguish individual males based solely on their airborne sexual advertisement calls. The males dwell within their own burrow systems in the ground and project their calls through a surface opening of an acoustic horn to attract females for mating. Cassette tape recordings were collected from targeted burrows during the calling season and coverted to digitized sound files using SIGNAL software. These files were then subjected to correlational analyses to determine if we could distinguish "same" from "different" with a high level of accuracy and repeatability. Athough other studies of insect sounds in this context have not been reported, recent success in identifying individual canaries, bats, wolves, etc. encouraged us to pursue this work. With the certainty of identification based on the call, new doors can be opened to the study of this and related species. Not only will male spacing and burrow establishment be open to new interpretation, but parameters of the calls of successful males can be examined to tease out the focus of female choice for the species.
26.1 FRANCIS, JR., A.W.*, TURINGAN, R.G., Florida Institute of Technology, Melbourne, Florida Institute of Technology, Melbourne. Functional implications of asymmetrical feeding biomechanics in pleuronectiform fishes.
Flatfishes (Order Pleuronectiformes) differ-from the generalized teleost morphology in that bilaterally symmetrical larvae metamorphose into bilaterally asymmetrical juveniles where one eye migrates to the opposite side of the head. The development of morphological asymmetry is expected to have profound consequences for flatfish feeding biomechanics, performance, and ecology. Biomechanical features associated with feeding in developing summer flounder, Paralichthys dentatus, were measured for both ocular (left) and blind (right) sides. Using principles from mechanical engineering, the measurement of lever arms responsible for lower jaw depression and elevation allowed for the determination of mechanical advantage for each side of the head. Mechanical advantage was then used to make functional predictions about feeding mode where the oral jaw lever system in fishes represents a compromise between speed of jaw movement and strength of bite. Analysis of variance or analysis of covariance revealed significant differences in lever arms and mechanical advantage between sides of the head of late metamorphic and early juvenile summer flounder. In particular, the ocular side is predicted to have a faster bite while the blind side is predicted to have a stronger bite. Work currently in progress will test predicted functional asymmetry using high speed recordings of feeding kinematics in developing flatfish.
37.5 FRANK, C.L., Fordham University. The nutritional ecology of food hoarding by red squirrels.
It has proposed that granivory and food hoarding coevolved repeatedly in mammals because seeds tend to retain their nutritional quality during storage, although this hypothesis has not been tested. The effects of prolonged storage on the nutritional composition of five conifer seed species hoarded by Mount Graham red squirrels, Tamiasciurus hudsonicus grahamensis, were examined in order to better understand the evolution of food storage. The results demonstrate that the nutritional quality of all conifer seed species examined decreases during storage by red squirrels, and three of the seed species no longer met the minimal nutritional requirements of red squirrels after 3–8 months of storage. This study demonstrates that the evolution of food hoarding by red squirrels was probably actually constrained by the nutritional properties of their primary food.
46.6 FREEMAN, G., University of Texas, Austin. A developmental basis for the Cambrian explosion: evidence from extant brachiopods.
Paleontological evidence indicates that a large number of new animal phyla, in addition to classes and orders within phyla, were first observed during the Cambrian. One possible basis for the genesis of new morphologies during this period may have been the ease with which developmental programs responsible for regional specification during early development could be changed. Subsequently these developmental programs are postulated to have become more tightly integrated, making changes in early development more difficult to effect and thereby reducing the variation that natural selection can operate on. Within the Linguliformea and Craniiformea, extant lingulids, discinids and craniids belong to orders that originated during the Cambrian. Within the Rynchonelliformea, extant rhynchonellids belong to the pentameride lineage that also originated during the Cambrian.The other order, Terebratulida, with extant families, originated via a series of intermediate forms, from a pentameride ancestor at the base of the Devonian. By comparing cleavage patterns, fate maps, patterns of morphogenetic movements during gastrulation, the timing of regional specification during early development, and the mechansisms responsible for regional specification in extant species one can assess whether there is more variation in the ways of going about early development in descendants of orders that originated during the Cambrian versus descendants of the Terebratulida which originated later. There are major differences in embryogenesis in groups that originated during the Cambrian. There are essentially no differences in the early embryologies of the rhynchonellid Hemithyris, and two representatives of the Terebratulida, although these forms are morphologically disparate.
2.1 FREUND, E.V.*, DEWAR, H., CROLL, FD.A., Harvard University, Cambridge, MA, PIER, Oceanside, CA, University of California, Santa Cruz. Locomotor tracking of the spine-tailed devil ray, mobula japanica.
Three-dimensional movements and foraging ecology of a small manta ray species, the spine-tailed devil ray, Mobula japanica, were monitored using acoustic tracking (n = 2) and archival tagging techniques (n = 4) in the southern Sea of Cortez. The rays ranged in size from 65 – 112 cm disc length (mean = 87.6 cm, n = 6) with track duration ranging from 21 to 28 hours. Simultaneous biophysical oceanographic profiling allowed examination of temperature profiles and prey distribution in relation to ray movements. The primary prey of these rays is krill, Nyctiphanes simplex, which remains at depth (150 m) in dense clouds during the day, then moves to the surface and disperses at night. The rays spent most of their time above the thermocline and appeared to forage at night when the krill swarms approach the surface. When krill were present the animals displayed a step-wise ascent pattern which may indicate foraging through clouds of krill. Maximum dive depth during one track reached 445 m. Consistent throughout the tracks was a dive and ascent pattern suggestive of burst and glide swimming. Tracking speed was typically 1 knot with bursts up to 4.5 knots. The rays traveled up to 30 miles in 24 hours and did not always remain in areas where krill density was high. Information on movements and habitat use is critical for understanding the impact of fisheries on manta ray populations. This impact is potentially high because of the mantasí low fecundity rates (1 pup per year). In addition to improving our understanding of their natural history, we hope this research will provide valuable information when management and conservation strategies are considered. Supported by National Geographic.
65.3 FRIEDRICH, M., Wayne State University, Detroit. Evolution of insect eye development: comparative and functional evidence for a conserved role of Wingless in negatively controlling the spatial extent of retina differentiation.
Molecular genetic studies in model organisms like mouse and Drosophila have identified a number of genes, which appear to be expressed and required in similar ways during eye development. Fundamental aspects of metazoan eye development are therefore likely to be evolutionarily conserved. Nonetheless, Drosophila exhibits a highly derived mode of insect eye development from imaginal discs, which may, to some degree, compromise its suitability for across phyla comparisons. It is also an important question, which developmental regulatory changes were involved in the transition from embryonic eye development in primitive insects to the advanced mode of postembryonic eye development in Drosophila. We are therefore studying eye development in the more primitive flour beetle Tribolium castaneum and the grasshopper Schistocerca americana. We have previously shown that the expression of the signaling factor Wingless in front of the differentiating retina is highly conserved indicating a conserved function in negatively regulating retina differentiation in insects. Consistent with this, we find that exposure of in vitro cultured grasshopper retinas to lithium, which constitutively activates Wingless signaling via inhibition of Glycogen synthase kinase-3, specifically blocks progression of retina differentiation. A detailed analysis of wingless expression during Tribolium embryogenesis revealed that Wingless is expressed in a manner consistent with a function in suppressing embryonic eye development thereby allowing only a small number of larval photoreceptors to differentiate and facilitating the delay of adult retina differentiation into postembryogenesis.
39.1 FRYE, M.A.*, DANIEL, T.L., University of Washington, Seattle, University of Washington, Seattle. Mechanical encoding properties of the wing hinge stretch receptor in the hawkmoth.
Insect flight emerges from complex interactions among patterned motor output, musculoskeletal mechanics, aerodynamic and inertial forces, and neural feedback. In the hawkmoth Manduca sexta, feedback from a wing hinge stretch receptor (SR) is crucial for the visuo-motor control of lift. Using a combination of extracellular recording, optical tracking, and high-speed video, we show that the SR undergoes sinusoidal length changes during tethered flight and fires a burst of spikes near the dorsal stroke reversal. We describe the mechanical encoding properties of the stretch receptor by comparing experimental data to the output of a computational model in an effort to better understand how this specialized sensory organ encodes forces and strains acting on the wing hinge. Using a mechanical actuator, we measured tissue tension, deformation, and SR spiking activity in response to controlled motions of the wing hinge. Step changes in tissue extension evoke an initial rapid increase followed by decay in both tension and SR firing rate. These time dependent responses were fit to models of the tissue and the SR that are comprised of viscous and elastic elements. We compared simulation output to experimental results using sinusoidal motion stimuli matching the in vivo deformations of thewing hinge. For such motions, the SR encodes timing, amplitude, and frequency of experimental wing hinge deformation. Model results closely match tissue tension seen in vitro, however the model does not capture the firing pattern of the stretch receptor. Thus, stretch receptor responses are not determined by simple linear models, and non-linear characteristics or active encoding dynamics are needed to explain the behavior of this mechanoreceptor. Supported by NSF.
P2.62A FUDGE, D. S.*, GOSLINE, J. M., University of British Columbia. Mechanical and optical properties of hagfish slime threads.
Hagfishes are unique in their ability to produce vast quantities of fiber-reinforced slime when they are provoked. In order to understand the material properties of hagfish slime, we investigated the properties of isolated slime threads from the Pacific hagfish ( Eptatretus stouti).The threads are manufactured within specialized cells called Gland Thread Cells (GTCs), which are found within the numerous slime glands. Each GTC produces a single, continuous, intricately coiled protein thread that unravels upon contact with seawater. We found GTCs to exhibit a bi-directional taper, being on average 3.0 ± 0.4 mm in diameter in the middle, and 1.0 ± 0.2, and 1.5 ± 0.2 mm in diameter at the two (distinct) ends. Slime threads were on average 12 ± 0.44 cm long in the unstrained state, but can be as long as 34 ± 1.2 cm when strained to the breaking point. Tensile tests of the threads in seawater revealed them to be quite extensible and strong, and therefore tough. Average extensibility (DELTA/Lo) in water was 1.8 ± 0.11, strength was 170 ± 24 MPa, and toughness was 100 ± 19 MJ/m3.Threads tested in air were stronger, stiffer, tougher, and less extensible than those tested in seawater. Average extensibility in air was 1.0 ± 0.10, strength was 520 MPa, and toughness was 270 ± 17 MJ/m3. Tensile tests performed in chaeotropic agents such as guanidine HCl suggest that the IF proteins that make up the threads are held together by non-covalent intermolecular forces. Birefringence data and evidence from Congo Red staining of strained and unstrained threads suggest that the low modulus plateau region of the stress-strain curves corresponds to a transformation of alpha-helical and/or globular domains of the constituent IFs to a more highly-ordered beta-sheet crystalline state.
S11.11 FULL, R.J., University of California, Berkeley. Stability and maneuverability in sprawled posture, legged locomotion.
Legged animals bounce up and down and side to side as they run. Species that differ in leg number and posture run stably like sagittal and horizontal plane spring-mass systems. Preflexive mechanisms at the level of legs permit passive, dynamic feedback that can reject rapid perturbations before sensor-based reflexes and thereby simplify control. A greater number of widely spaced, compliant legs potentially in contact with the substrate provide for robust, dynamic selfstabilization. Legs of sprawled posture runners produce lateral and opposing ground reaction forces, since these vectors tend to minimize joint moments by aligning along the leg axially. Front legs tend to decelerate the body, while rear legs only accelerate the center of mass. All legs tend to push away from the body. Differential leg function in sprawled posture runners not only permits greater stability, but also greater maneuverability. Maneuvers can require minor neuromechanical alterations to straight-ahead running. A small change in force production can generate turning and climbing without large changes in leg kinematics. A greater number of widely spaced, compliant legs potentially in contact with the substrate provide for greater maneuverability because of an increased opportunity to shift the center of pressure. Legged animals appear to manage energy in a way that works with their natural dynamics. Principles from sprawled posture runners are being used to inspire the design of highly mobile, autonomous physical models ñ robots. Supported by DARPA/ONR N00014-98-1-0747 and ONR N00014-98-1-0669.
S8.1 FULL, R.J., University of California, Berkeley. Bestowing biological inspiration and getting novel insight from engineering and entertainment.
Discoveries and principles in biology can provide inspiration for design in robotics, animatronics, animation and architecture. Unique materials and structures, remarkable functional relationships and the spectacularly effective performance found in natural technologies provide a wealth of ideas. Yet, blind, direct copying of biology is rare and often fails. Nature provides useful hints at what is possible. In most cases, it is more valuable to use concepts and analogies when advantageous. Natureís designs are constrained by development, history, function and Newtonís Laws. Human creations often extend beyond biological capabilities and can be made to be more effective. The flow of ideas is in no way unidirectional. In fact, historically, there has been more transfer from engineering, physics and mathematics to biology than the reverse (Vogel, 1998). The conception and construction of artificial technologies has been extremely important in providing novel hypotheses and instrumentation to biology. Multidisciplinary experiences can benefit biological research directly and indirectly through the fostering of lateral thinking. The mutually beneficial reciprocal relationships between biology and engineering, computer science and entertainment are increasing exponentially. We are the verge of a revolution in the Age of Integration.
S14.2 FURLOW, J.D.*, LIM,W., ERMIO, D.J., CHIELLINI, G., SCANLAN, T.S., University of California, Davis, University of California, Davis, University of California, Davis, University of California, San Francisco, University of California, San Francisco. Molecular mechanisms underlying thyroid hormone induced gene expression cascades during amphibian metamorphosis.
Amphibian metamorphosis is an excellent system to understand nuclear receptor function during development. Thyroid hormone (TH) induces a wide range of morphological changes by regulating gene expression via a pair of nuclear receptors, TH receptor ALPHA (TRALPHA) and TH receptor BETA (TRBETA). Our laboratory is interested in how this dramatic tissue specific transcriptional control by TH occurs. Previous expression studies in the frog Xenopus laevis implicated TRALPHA in adult tissue formation and TRBETA in larval tissue resorption. We employed the TRBETA selective agonist GC-1 as a pharmacological probe of TR function. In transfection assays, GC-1 activated Xenopus TRBETA 20-fold better than Xenopus TRALPHA, compared to the natural ligand T3. In GC-1 treated tadpoles, tail and gill resorption was efficiently induced with little effect on limb growth. In addition, GC-1 preferentially activated a subset of TH-response genes in the tail, including several protease genes. We are currently screening additional synthetic TH analogs, as well as exploring other means to specifically manipulate TR isotype activity in living cells. Finally, we are characterizing the regulatory control regions of several TH response genes in vivo using transgenesis. We have shown that the TH/bZIP promoter drives green fluorescent protein (GFP) expression in transgenic tadpoles in a proper temporal and spatial pattern. Our initial studies with the fibronectin promoter, a late TH response gene at metamorphosis, showed a high level of GFP expression in gastrulating embryos, as expected. We are now following GFP expression driven by wild type and mutated fibronectin promoter constructs throughout development.
P3.87 GAINEY, JR., L.F.*, CHICOINE, D., WALTON, J., GREENBERG, M.J., University of Southern Maine, Portland, University of Southern Maine, Portland, University of Southern Maine, Portland, C.V. Whitney Lab, University of Florida, St. Augustine. Hydrogen sulfide potentiates muscle contraction in clam gills.
When isolated gills of Mercenaria mercenaria are treated with 5-hydroxytryptamine (5HT), the branchial musculature contracts in a dose dependent manner. Moreover, a second application of 5HT at the same concentration produces a larger contraction; this effect is mediated by nitric oxide (NO) synthesized in the muscles. Since NO and hydrogen sulfide (H2S) both modulate muscle contraction in mammalian vascular smooth muscle and because Mercenaria is exposed to H2S in the environment, we investigated the effects of H2S on gill muscle contraction. When gills were pretreated with 10–6 M H2S and then exposed to increasing concentrations of 5HT, the dose response curve was shifted to the left and the maximal contraction increased in comparison with untreated controls. With 10–6 M H2S, the concentration of 5HT giving a half maximal contraction (EC50) was 1.1 x 10–5 M and the maximal contraction was 32% of the resting length at 10–4 M 5HT. In untreated gills, in contrast, the EC50 was 2.8x10–5 M and the maximal contraction was only 12%. Finally, when gills were pretreated with increasing concentrations of H2S and then exposed to 2x10–5 M 5HT, the contractions were potentiated in a dose dependent manner. The threshold for potentiation was 10–10 M H2S, and the effect became maximal between 10–8 and 10–5 M. Supported by grants from the Maine Science and Technology Foundation and the University of Southern Maine (LFG).
P1.62 GALE,H.H., Creighton University Intermittent breathing in very large mammals.
Breath holding is common in reptiles. Intermittent breathing also occurs in very large mammals; whale, elephant, rhinoceros, hippopotamus, and giraffe. Both groups have low rates of metabolism. Ectothermy allows the low rates of reptiles. Endotherms have higher metabolic rates that are inversely related to body size. Hence the mass specific metabolic rate of a 4000 kg elephant is about the same as a 1 kg monitor lizard. Low metabolic rates are coupled to low breathing frequencies, 6 breaths per minute (bpm) for the elephant and 3 bpm for the lizard. At low bpm, intermittent breathing reduces the cost of ventilation. Continuous slow breathing has lower airflow velocities that decrease the frictional resistance to both laminar and turbulent flow. But brief rapid discontinuous breaths use less energy overall because very slow respiratory muscle contraction is extremely inefficient. A female African elephant weighing about 4000 kg was videorecorded during rest. Thoracic movements were analyzed frame by frame with a potential accuracy of 1/30th sec. Breath frequency, bpm; and the durations of: inspiration Ti, expiration Te, and the pauses between breaths Tp; were measured. Average values were; bpm 5.8, Ti 3.1 sec, Te 1.9 sec, Tp 5.1 sec. Breath holding was in the inspiratory position. Initial observations of rhinoceros and giraffe were qualitatively the same, but with higher bpm and shorter durations that correlate with smaller body masses. This ventilatory pattern is reminiscent of reptilian inspiratory breath holding and active expiration of shorter duration than passive inspiration. Inspiratory pauses have the advantage of a larger air volume to draw upon during apnea. Whether the breathing pauses of very large mammals are also at respiratory system relaxation volume, thus requiring no muscular effort, remains to be tested.
P3.103 GALIMA, M.*, KELLEY, K.M., California State University at Long Beach, California State University at Long Beach. Relationship between the physiological stress response, serum IGFBPs, and growth in the jack mackerel.
Metabolic and somatic growth parameters were assessed in Trachurus symmetricus subjected to confinement and handling stressors. Mackerel were caught offshore near Catalina Island and placed into 50-L circular aquaria for 5 d without further disturbance ("confinement" group) followed by blood serum collection, or they were subjected to an additional 30 or 60 min of handling stress prior to blood sampling (" handling" groups). Controls were caught and immediately sampled (within 2 min). Confinement alone increased serum concentrations of glucose (>2-fold, p<0.01) and resulted in 6-fold elevations in cortisol (p<0.001), as compared with corresponding levels in control fish. With the additional handling, cortisol concentrations were elevated yet further as compared with that in the confinement group (p<0.05 at 60 min), while glucose levels did not show this trend. Serum profiles of the insulin-like growth factor-binding proteins (IGFBPs) exhibited changes reflective of a growth-inhibited state in the stressed mackerel, with the greatest magnitude of such changes evident in the individuals with the highest cortisol levels. Results thus far suggest that stress-associated cortisol may play an inhibitory role in growth via changes in the IGF system. [Support by NSF grant IBN-9600783 & NIH grant #GM50089].
47.4 GALIS, F., Leiden University. Modularity and the conservation of characters determined in the phylotypic stage.
The phylotypic stage is the developmental-stage at which vertebrates most resemble each other. In an earlier study we found support for Raff's hypothesis that the remarkable conservation of the phylotypic stage in vertebrates is due to the high number of ongoing interactions. Interestingly, the lack of modularity of inductive interactions at that stagemay not only have conserved this embryonal stage more than other developmental stages, but may also have had consequences for the conservedness of adult characters determined in this stage. Possible examples are the number of digits in amniotes and the number of cervical vertebrae in mammals. Evidence will be discussed. I end by presenting an argument why the absence of modularity in the inductive interactions may also be the root cause of the conservation of the much discussed temporal and spatial colinearity of the Hox genes in the phylotypic stage of vertebrates.
P2.71 GALLARDO, L.I.*, NISHIKAWA, K.C., Northern Arizona University, Flagstaff, Arizona University, Flagstaff. Ecomorphology and locomotion of Sceloporus.
Comparative analyses of iguanian lizard morphology have shown that certain body proportions are consistently associated with particular microhabitats. This result suggests that a single genus with ecologically diverse species will exhibit morphological variation reflecting their ecological niches. Morphological measurements were taken from species of Sceloporus of varied microhabitat specialization, ranging from ground dwellers to saxicolous species. Saxicolous species, which regularly encounter incline in their habitat are expected to exhibit a lower length ratio between the most distal and proximal joints than ground-dwelling species. Saxicolous species are also expected to have proportionally shorter hind limbs when compared to those of ground dwellers. Likewise, locomotor kinematics and performance variables are expe