Review Article
Dirk Weihrauch1,*, Steve Morris2 and David W. Towle3
1 Department of Biology, Division of Animal Physiology, University of Osnabrück, D-49076 Osnabrück, Germany
2 Morlab, School of Biological Sciences, University of Bristol, BS8 1UG, UK
3 Mount Desert Island Biological Laboratory, Salsbury Cove, ME 04672, USA
* Author for correspondence at present address: Department of Biology, Division of Animal Physiology, Universität Osnabrück, D-49076 Osnabrück, Germany (e-mail: Weihrauchblues@gmx.net )
Summary
The excretory transport of toxic ammonia across epithelia isnot fully understood. This review presents data combined withmodels of ammonia excretion derived from studies on decapodcrabs, with a view to providing new impetus to investigationof this essential issue. The majority of crabs preserve ammonotelyregardless of their habitat, which varies from extreme hypersalineto freshwater aquatic environments, and ranges from transientair exposure to obligate air breathing. Important componentsin the excretory process are the Na+/K+(NH4+)-ATPase and other membrane-boundtransport proteins identified in many species, an exocytotic ammoniaexcretion mechanism thought to function in gills of aquaticcrabs such as Carcinus maenas, and gaseous ammonia release foundin terrestrial crabs, such as Geograpsus grayi and Ocypode quadrata.In addition, this review presents evidence for a crustaceanRhesus-like protein that shows high homology to the human Rhesus-likeammonia transporter both in its amino acid sequence and in itspredicted secondary structure.
Key words: ammonia excretion, ammonia transporter, crab, exocytosis, Rhesus-like protein, Na+/K+-ATPase
Journal of Experimental Biology 207, 4491-4504 (2004). Published by The Company of Biologists 2004.
Answers to all your Biology Questions
