9419849 Claiborne The long range goal of this project is to understand how marine fish are able to use their gills to accomplish many of the same tasks that are performed by the kidneys in mammals. The fish gill is a multi-purpose organ. Analogous to the lungs in land-dwelling animals, the gills allow the fish to breath oxygen and excrete carbon dioxide. Further, the gills perform functions of the liver and kidneys as they eliminate toxic metabolic waste products like ammonia and acid. Also analogous to the kidneys, the gills assist the fish by regulating the levels of salts within the blood of the animal. Little is known about the actual cellular mechanisms which take place within the gill tissue. Dr. Claiborne has hypothesized that some saltwater fish may take in salt (sodium) from the surrounding water to excrete excess acid from within the body. The species which have this ability may then be able to live in a wider range of salt water environments, from the open ocean, to dilute estuaries. This proposal will study these gill mechanisms in two different species of marine fish, the sculpin, and the toadfish. His preliminary findings suggest that the sculpin may not be able to excrete sufficient acid when external salt levels are too low. In contrast, the toadfish can regulate acid levels in a wide range of saltwater concentrations. Thus, by comparing the acid excretion mechanisms in these two species, it will be shown whether the gills play a role in determining the environmental salinity range in which a fish species can live. Further, since these cellular mechanisms within the gills are very similar to those currently being studied in the mammalian kidney, new insights into the physiology of the kidney and other organs may also be elucidated. ***
