Development of the aerobic dive limit and muscular efficiency in northern fur seals (Callorhinus ursinus) |
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Authors: | Michelle R Shero Russel D Andrews Keri C Lestyk Jennifer M Burns |
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Institution: | (1) Department of Biological Sciences, University of Alaska Anchorage, Anchorage, AK 99508, USA;(2) School of Fisheries and Ocean Sciences, University of Alaska Fairbanks, Fairbanks, AK 99775, USA;(3) Alaska SeaLife Center, Seward, AK 99664, USA |
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Abstract: | Northern fur seal (Callorhinus ursinus; NFS) populations have been declining, perhaps due to limited foraging ability of pups. Because a marine mammal’s proficiency
at exploiting underwater prey resources is based on the ability to store large amounts of oxygen (O2) and to utilize these reserves efficiently, this study was designed to determine if NFS pups had lower blood, muscle, and
total body O2 stores than adults. Pups (<1-month old) had a calculated aerobic dive limit only ~40% of adult females due to lower blood
and, to a much greater extent, muscle O2 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 ~50%; LD ~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, β-hydroxyacyl CoA dehydrogenase, and lactate dehydrogenase activities (all P values ≤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. |
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