Marine bivalve molluscs such as oysters, clams and mussels often are found in habitats where oxygen availability may vary dramatically with time. For instance, species which live in the intertidal zone may go through daily cycles of air exposure at low tides. Most species close their shells to avoid desiccation. However, this results in a severe depletion of internal oxygen since the organism is effectively sealed from the respiratory environment. Surprisingly, many of these species survive without oxygen for extended periods due to the ability of their cells to produce energy in the absence of oxygen. One major drawback in making energy without oxygen is that metabolic acids accumulate as waste products. This study will investigate how the cells of these animals deal with the metabolic acids produced during period of hypoxia. Experiments will be conducted to see if cells from high intertidal species (frequent exposure to oxygen deprivation) show a higher capacity for dealing with these metabolic acids than cells from low intertidal species (infrequent exposure to oxygen deprivation). Additional studies will investigate whether the capacity for cells to cope with acid loads is enhanced when animals are subjected to chronic oxygen stress. These studies will provide information on the unique mechanisms by which these animals are adapted to their habitats and also yield insights into general mechanisms applicable to higher organisms.//
