Skip Navigation

American Zoologist 1985 25(3):671-688; doi:10.1093/icb/25.3.671
© 1985 by The Society for Integrative and Comparative Biology
This Article
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Alert me to new issues of the journal
Right arrow Add to My Personal Archive
Right arrow Download to citation manager
Right arrow Request Permissions
Google Scholar
Right arrow Articles by PENNAK, R. W.
Right arrow Search for Related Content
Social Bookmarking
Add to CiteULike   Add to Connotea   Add to Del.icio.us  
What's this?

The Fresh-water Invertebrate Fauna: Problems and Solutions for Evolutionary Success1

ROBERT W. PENNAK
EPO Biology, University of Colorado Boulder, Colorado 80309

The volume of salt waters of the world is more than 10,000 times the highly fragmented volume of inhabitable fresh waters, yet the latter has come to support a rich and euryokous fauna. In making the salt-brackish-fresh transition, the fresh-water (carbonate) fauna has developed clusters of new adaptations. The vast majority of marine species are restricted to a narrow and monotonous chemical environment, but most freshwater species thrive in habitats exhibiting a wide (e.g., 10-fold) range of dissolved salts, featuring high carbonates, low sodium chloride, and low potassium.

In comparison with their ancestral marine forms, the temperate fresh-water fauna is generally characterized by: (1) much more efficient osmoregulatory systems, (2) smaller body size, (3) lower reproductive potential, (4) loss of specializedlarval stages, (5) a wide variety of anabiotic devices and strategies, (6) well developed low temperature tolerances, (7) aestivation stages in adults, (8) a remarkable facility for overland geographical migration and ecesis by disseminules, (9) facility and adaptations for withstanding prolonged habitat silting, (10) adaptations to swift unidirectional currents by many lotic species, and (11) a more general ability to live anaerobically.

Certain characters of the marine biota have usually been lost during transition and ecesis in the fresh-water environment, such as bioluminescence, bright body coloration, and distinctive bright color patterns. Morphological embellishments in the marine biota are common, including cirri, palps, setation, protuberances, and respiratory devices, but such structures are uncommon among fresh-water species. It is suggested that respiratory stratagems have been developed to an excessive and "unnecessary" degree among many marine forms, as well as in a few fresh-water insects and most Eubranchiopoda.


Add to CiteULike CiteULike   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us    What's this?




Disclaimer:
Please note that abstracts for content published before 1996 were created through digital scanning and may therefore not exactly replicate the text of the original print issues. All efforts have been made to ensure accuracy, but the Publisher will not be held responsible for any remaining inaccuracies. If you require any further clarification, please contact our Customer Services Department.