Freshwater mussels are successful ionic- and osmotic-regulators but they maintain blood ion concentrations well below other freshwater animals. Using various procedures including ion fluxes, ion substitution studies, isolated tissue techniques, morphology and histochemistry, cAMP and prostaglandin biochemistry, we have demonstrated that the gill is the a major site of ionic regulation. We have found that freshwater mussels transport Na, K, Rb, and Cl at rates that equal or exceed the transport rates found inmost freshwater forces involved in ion transport, the electrical gradient across gill epithelial cells must be measured. In addition, the types and their respective conductances of ion channels present in epithelial cell membranes will be determined using the inside-out patch clamp technique. Preliminary data indicate that mussel membranes have ion channels with remarkably high (>300 pS) conductances. These studies will provide information about how mussels function with low blood ionic strengths, and yet tolerate substantial modification of blood ion composition when subjected to changes in their environment. Understanding the cellular mechanisms that allow freshwater mussels such remarkable adaptations is relevant to our understanding of the limits at which cells and organisms can function. //
