Congeneric marine fishes and invertebrates with different latitudinal or depth distribution patterns, i.e., different absolute temperatures and thermal ranges, will be studied to determine: (1) the importance of fine-scale adaptations to temperature in kinetic properties and structural stabilities of enzymes; (2) the amino acid sequence changes that underlie these adaptive differences in kinetic and stability characteristics; (3) the roles played by multi-locus and allelic enzyme variants in adaptation to temperature over evolutionary and seasonal time course; (4) the effects of evolutionary adaptation and seasonal acclimatization on mitochondrial respiration and membrane fluidity; and (5) the kinetics of acclimatory change in protein isoforms and mitochondrial respiration and fluidity. These studies are designed to fill in important gaps in our understanding of the thermal biology of animals, specifically the role played by fine-scale adaptation to temperature in establishing organismal distribution patterns, the precise changes in protein primary structure that establish adaptive differences in enzymes(M4 - lactate dehydrogenase and cytosolic malate dehydrogenase), the minimal amounts of change in temperature required to favor selection for new protein variants or mitochondrial properties, and the rate with which acclimation occurs. Comparisons of eurythermal and stenothermal congeners will reveal underlying biochemical and molecular differences that help to establish species' thermal tolerance ranges. Study of fine-scale adaptations to temperature will provide a firmer basis for predicting the effects of global warming on the distributions and functions of economics animals.
