Meeting Abstract

P1.73  Jan. 4  Seasonal correlations of muscle biochemistry and body condition in adult harbor seals in Glacier Bay, Alaska PREWITT, Jill*; BURNS, Jennifer; BLUNDELL, Gail; University of Alaska Anchorage; University of Alaska Anchorage; Alaska Dept. of Fish and Game jsprewitt@gmail.com

Phocid seals� muscles display a suite of physiological adaptations that allow them to function during dives when oxygen is not freely available: high myoglobin concentrations [Mb], high densities of Type I (slow oxidative) and Type IIa (fast oxidative-glycolytic) fibers, and high aerobic and anaerobic enzyme activities. Phocid seals also show large seasonal shifts in body composition that are associated with shifts in diet and/or life history events such as reproduction and molt. In terrestrial species, changes in diet and body condition are known to impact fiber type densities, fiber diameters, lipid droplet densities, and enzyme activities. For diving seals, such changes could impact their ability to dive, and therefore forage efficiently. To determine if muscle biochemistry changes seasonally in association with shifts in body condition, we measured body condition (% lipid, via deuterium labeled water) and collected muscle biopsies from adult harbor seals (Phoca vitulina) in Glacier Bay, Alaska across different seasons (Fall n=15; Spring n=15). We examined the correlation between body condition, muscle enzyme activities (LDH, CS, HOAD), and [Mb]. We found that, despite increases in body condition from fall to spring, there were no significant differences in enzyme activities between the two seasons. This suggests that muscles do not rely more heavily on lipid based metabolism during periods where body condition is increasing. Future research will include determining muscle fiber types, lipid and glycogen stores, mitochondrial densities, and capillary densities using light and transmission electron microscopy.