© 2003 by The Society for Integrative and Comparative Biology
Invertebrates
1 Department of Biology, University of Washington, Seattle, Washington 98195
Invertebrates. RICHARD C. BRUSCA AND GARY J. BRUSCA. Sinauer Associates, Sunderland, Massachusetts, 2002, 936 pp. (ISBN 0-87893-097-3, $109.95).
The new edition of Brusca and Brusca's Invertebrates propels it into the lead as the most up-to-date of the large (
1,000 pages), thorough invertebrate biology textbooks, suitable for two-quarter or intensive semester senior-level courses. The most recently revised competitor is Ruppert and Barnes' Invertebrate Zoology, 6th edition of 1994, and a great deal has happened in the field in the past decade.
Only 14 pages longer than its predecessor, the new Brusca and Brusca has a much more pleasing, user-friendlier format with more prominent subheads to guide the reader. Many monochrome photos of the first edition now burst forth in vivid living color, and the paper quality has improved to accommodate them. The book displays the high production standards typical of the publisher. New color photos of excellent quality also document newly incorporated topics. For example, the recently discovered carnivorous sponges are seen in action trapping mysids, while scanning electron micrographs reveal details of the capture. The authors use SEMs to good advantage to illustrate recent findings, but labeling of key structures would have rendered them more reader-friendly. Examples are the habitus of Cycliophora, a phylum first described in 1995, and the recently discovered, beautifully preserved Cambrian meiofaunal crustaceans from Sweden.
The thoroughly revised introductory chapter is longer, clearer, and more tightly written but has many footnotes and remains terminology- and jargon-intensive. Chapter 2 discusses general principles of classification, systematics, and phylogenetics. Chapter 3, "Animal architecture and the bauplan concept," emphasizes the bauplan as an organism-level property. It fails to alert the student that this concept will be used more conventionally in subsequent chapters, as the phylum-level body plan. This chapter, and the next on development and life history, summarize general zoology well and usefully, particularly because courses in that subject are now rare.
The next 19 chapters march through the phyla, in somewhat reordered fashion from the first edition. The first edition's chapter on Protozoa recognized 7 phyla. Rewritten with Diana Lipscomb and Kristen Kivimaki, it now covers all 17 phyla of Protista in the same space. The chapters on Metazoa include some very recent discoveries, e.g., the insect Order Mantophasmatodea, first published in 2002. For the most part, however, the significant but mainly cosmetic improvements in illustration predominate over substantive revision. Quite a few chapters are textually essentially identical to their predecessors. These attained a high level of accuracy, but the new edition fails to incorporate some significant advances. For example, in an unchanged section nutrition in perviate pogonophorans is still stated to be unknown, despite the convincing demonstration that Siboglinum is "gas-powered" by endosymbiotic methanotrophic bacteria (Schmaljohann et al., 1990
). And while the authors recognize publication of the complete genome of Caenorhabditis, they do not mention how its complete cell lineage, in concert with genetic studies, has generated broadly important new insights into the development of body organization (e.g., Thomas, 1994; Blaxter, 1998).
Invertebrates differs from most of its extant congeners in organizing the chapters on the larger phyla by functional systems rather than by class. That is, rather than being the primary topics, classes are subtopics under main headings of body form and anatomy, support and locomotion, feeding and digestion, circulation and gas exchange, excretion and osmoregulation, nervous system and sense organs, and reproduction and development. Both arrangements are equally logical, but in my teaching experience students learned a complex subject more easily when class-level taxa were the primary categories. This is especially true in the laboratory, where study and dissection of one representative organism can reveal all the systems and their interrelationships. Laboratory work organized according to this text also requires using many more specimens to teach the same material. Moreover, the systems-first organization causes some awkwardness in presentation. For example, although the authors accept the recent assignment of Pogonophora as a family of polychaetes, the section on annelid feeding and digestion omits their fascinating nutrition, because they are treated separately as an added section of the chapter.
More than its competitors, Brusca and Brusca's text explicitly addresses phylogeny, but in a "bookended" fashion. As in the first edition, the second and last chapters treat phylogeny, the former theoretically, the latter primarily at the phylum level. This was one of the most active research areas in invertebrate biology in the late 1990s alluded to above. However, Chapter 2 retains the first edition's three traditional, still confusing evolutionary trees of phyla and higher taxa. Despite lip service to explicit phylogenetic hypotheses (p. 34) modern higher classifications based on cladistic analyses are not mentioned here. Much evidence relevant to phylogenetic hypotheses from new, independent character sets has appeared in the last decade. The authors acknowledge this, but they barely mention it in the main discussions of the phyla and discuss it explicitly only in the final four pages. The relevant molecular papers are cited but are given short shrift, and the new groupings of phyla they have generated are relegated to "other ideas about phylogeny." The only phylogenetic tree of metazoan phyla presented in Ch. 24 is a morphology-based cladogram that updates the first edition's and includes more phyla.
For a book that explicitly emphasizes phylogeny, attention to molecular phylogenetics is thus surprisingly limited, given that the new gene sequence data stimulated explicit hypotheses that re-energized phylum-level metazoan phylogenetics in the 1990s and also motivated morphological re-examinations. The recent trees based on gene sequences support some parts of the older morphology-based tree (e.g., the sister-group relationship of echinoderms, hemichordates and chordates, and inclusion of pogonophorans within Annelida). But in other parts the morphology- and molecular-based trees are presented as quite at odds (e.g., the Lophotrochozoa and Ecdysozoa clades that appear in the latter but not the former). The authors defend their rejection of these latter two groupings of phyla by citing conflicting molecular analyses, but they fail to cite recent morphological support of this rearrangement and increased congruence of trees based on the two disparate approaches (Peterson and Eernisse, 2001). The authors' phylogenetic arguments would have been stronger and educationally more stimulating had they compared and contrasted the advantages and shortcomings of both molecular and morphological approaches to hypothesizing phylogenies.
Instructors who want their students to take advantage of the book's evolutionary emphasis to use these still controversial and unresolved hypotheses as an educational tool (to teach students how new discoveries affect the sometimes fitful and controversial advance of science) will be challenged. They will need to assign the last chapter early in the course and to supplement it with pertinent primary literature, including the papers cited here and in the book and other recent and provocative sources, such as Adoutte et al., (2000), Garey (2002) and those following the latter in the symposium on evolution of lesser-known protostomes in Volume 42, no. 3, of this journal.
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Adoutte, A., G. Balavoine, N. Lartillot, O. Lespinet, B. Prud'homme, and R. de Rosa. 2000. The new animal phylogeny: Reliability and implications. Proc. Natl. Acad. Sci. U.S.A, 97:4453-4456.
Blaxter, M. 1998. Caenorhabditis elegans is a nematode. Science, 282:2041-2045.
Garey, J. R. 2002. The lesser-known protostome taxa: An introduction and a tribute to Robert P. Higgins. Inegr. Comp. Biol, 42:611-618.
Peterson, K. J., and D. J. Eernisse. 2001. Animal phylogeny and the ancestry of bilaterians: Inferences from morphology and 18S rDNA sequences. Evol. Dev, 3:170-205.[CrossRef][Web of Science][Medline]
Schmaljohann, R., E. Faber, M. J. Whiticar, and P. R. Dando. 1990. Co-existence of methane- and sulphur-based endosymbioses between bacteria and invertebrates at a site in the Skaggerak. Mar. Ecol. Progr. Ser, 61:119-124.
Thomas, J. H. 1994. The mind of a worm. Science, 264:1698-1699.
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