RUI: Molecular Aspects of Salinity Acclimation in EuryhalineCrabs

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The proposed research will lead to new information regarding the molecular processes by which animals respond to environmental change. The model system employed is the euryhaline crab, an animal capable of adjusting to broad changes of salinity, at the same time maintaining a relatively constant salt level in the blood. The process by which the crab regulates its blood salt includes two transport systems at opposite ends of the cells making up the gill lining. One system brings sodium ions into the cell from the ambient water, in exchange for hydrogen ions, thus helping to regulate the acid-base status as well as the ionic level of the animal. The other system pumps sodium ions from the cell into the blood, this time in exchange for potassium or ammonium ion. A similar mechanism operates in the mammalian kidney, retaining sodium ions while hydrogen ions and ammonium ions are excreted. The advantage of studying the crab is that the animal naturally experience wide fluctuations in demand on the sodium transport systems. The approach will be to examine the molecular responses of the crab to salinity change, including changes in the synthesis or degradation of specific RNA and protein molecules. Both the sodium/hydrogen ion exchanger and the sodium/potassium pump will receive detailed attention in the research program.//