Many estuarine or intertidal fishes are exposed to fluctuating salinities, while other fishes migrate between freshwater and marine sites. These animals' solute balance might change drastically, but they maintain concentrations of their body fluids in a relatively narrow range with a suite of behavioral, systems-level, cellular, and biochemical adaptations to offset the passive fluxes of water and ions. Because the gill is responsible for the majority of gas exchange, elimination of nitrogenous waste, acid-base balance, and osmoregulation in virtually all teleost fishes, it represents a key interface between animal and environment. Relatively little attention has focused on chemical and physical properties of the plasma membranes of the gill that make up this interface. Dr. Crockett will test the hypothesis that lipid compositions of apical plasma-membrane domains from the gill are significantly different in freshwater- and seawater-acclimated fishes. Lipid changes are likely to occur in order to (1) ensure membrane integrity and permeability properties, (2) reduce changes in surface-charge density, (3) maintain such membrane physical properties as order and phase state, and (4) provide a micro-environment that permits sufficient activity of membrane-associated proteins. During the 18-month planning period, Dr. Crockett will characterize restructuring of the lipid components in gill plasma-membrane domains from fishes during adaptation to varying environmental salinities. This work will establish which lipid class(es) (phospholipids, glycolipids, cholesterol) is (are) involved in salinity adaptation. Results will (1) establish a protocol to prepare simultaneously gill apical and basolateral domains and (2) provide the first look at gill plasma-membrane restructuring during salinity adaptation in fishes.
