Meeting Abstract

P3.58  Wednesday, Jan. 6  Variation in mitochondrial properties in the muscle of two sub-species of killifish, Fundulus heteroclitus, during thermal acclimation. DHILLON, R.S.*; SCHULTE, P.M.; University of British Columbia; University of British Columbia dhillon@zoology.ubc.ca

Killifish, Fundulus heteroclitus, inhabit salt marshes and estuaries along the Atlantic coast of North America from New Brunswick to northern Florida. Previous studies have detected differences in metabolic rate between northern and southern sub-species of killifish. In this study, we explain these differences in metabolism by comparing factors that influence mitochondrial properties. Fish of each sub-species were acclimated to 5, 15, and 25 ºC. Adenylate status (indicative of signals activating the mitochondria), cytochrome oxidase and citrate synthase enzyme activities (indicative of mitochondrial content), and lactate dehydrogenase and creatine kinase enzyme activity (indicative of cytosolic metabolic capacity) were measured. Whole-body fiber typing and capillary density was used to compare muscle ultrastructure in the two sub-species. Mitochondrial enzyme activities were greater in the northern sub-species at all but the highest acclimation temperature, suggesting higher mitochondrial content in cold adapted northern fish. The relative proportion of oxidative:glycolytic muscle fibers were larger in the northern sub-species than the southern sub-species at all acclimation temperatures. Mitochondrial volume density and cristae surface density were also analyzed using TEM. Together these data suggest that differences in metabolic rate are related to differences in mitochondrial properties.