Development of the aerobic dive limit and muscular efficiency in northern fur seals (Callorhinus ursinus)

作者：Shero Michelle R^*; Andrews Russel D; Lestyk Keri C; Burns Jennifer M

来源：Journal of Comparative Physiology B: Biochemical, Systemic, and Environmental Physiology , 2012, 182(3): 425-436.

DOI：10.1007/s00360-011-0619-6

• Aerobic dive limit
• Oxygen stores
• Muscle development
• Myosin heavy chain
• Enzyme
• Diving physiology
• Northern fur seal

Northern fur seal (Callorhinus ursinus; NFS) populations have been declining, perhaps due to limited foraging ability of pups. Because a marine mammal%26apos;s proficiency at exploiting underwater prey resources is based on the ability to store large amounts of oxygen (O-2) and to utilize these reserves efficiently, this study was designed to determine if NFS pups had lower blood, muscle, and total body O-2 stores than adults. Pups (%26lt;1-month old) had a calculated aerobic dive limit only similar to 40% of adult females due to lower blood and, to a much greater extent, muscle O-2 stores. Development of the Pectoralis (Pec) and Longissimus dorsi (LD) skeletal muscles was further examined by determining their myosin heavy chain (MHC) composition and enzyme activities. In all animals, the slow MHC I and fast-twitch IIA proteins typical of oxidative fiber types were dominant, but adult muscles contained more (Pec similar to 50%; LD similar to 250% higher) fast-twitch MHC IID/X protein characteristic of glycolytic muscle fibers, than pup muscles. This suggests that adults have greater ability to generate muscle power rapidly and/or under anaerobic conditions. Pup muscles also had lower aerobic and anaerobic ATP production potential, as indicated by lower metabolically scaled citrate synthase, beta-hydroxyacyl CoA dehydrogenase, and lactate dehydrogenase activities (all P values %26lt;= 0.001). In combination, these findings indicate that pups are biochemically and physiologically limited in their diving capabilities relative to adults. This may contribute to lower NFS first year survival.

• 出版日期2012-4