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

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 (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 (<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 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 ~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.

Scaling matters: incorporating body composition into Weddell seal seasonal oxygen store comparisons reveals maintenance of aerobic capacities

“…Within species, the ADL and dive durations increase during ontogeny (Kooyman et al 1983;Burns and Castellini 1996;Richmond et al 2006;Burns et al 2007;Fowler et al 2007;Weise and Costa 2007;Shero et al 2012). However, among adults the relationship is less clear, and in this study larger Weddell seals had lower mass-specific TBO 2 stores than smaller seals.…”

“…Gels were silverstained and developed as described by Blough et al (1996) and bands were quantified using digitizing software (UN-SCAN IT gel v. 6.1). The identity of Weddell seal MHC I, IIA, and IID/X bands was determined by comparing their relative migration distances to those in the rat standard, and those of other pinnipeds that had previously been confirmed by proteomic analysis (Shero et al 2012) at the Ohio State University Mass Spectrometry and Proteomics Facility. New proteins were identified using capillary-liquid chromatography tandem mass spectrometry (Cap-LC/ MS/MS) using a Thermo Scientific LTQ mass spectrometer (Bruker Daltonics Billerica, MA) and LC system (UltimMateTM 3000 System, Thermo Scientific).…”

Influence of environment, morphology, and instrument size on lactating northern fur seal Callorhinus ursinus foraging behavior on the Lovushki Islands, Russia

“…However, for adult female northern fur seals on Lovushki, with sizes ranging from 28.7 to 58.9 kg, we found no relationship between diving behaviors and size. This may be because they typically made dives that were 1−2 min shorter than their calculated aerobic dive limit (cADL) of 2.6 min (Shero et al 2012). Size may only influence female fur seal behavior when they are forced to dive at or near their physiological limits (Costa et al 2001, Staniland et al 2010.…”

Preparing Muscles for Diving: Age-Related Changes in Muscle Metabolic Profiles in Harp (Pagophilus groenlandicus) and Hooded (Cystophora cristata) Seals

“…In addition, the notable variation in [Mb] that exists among different skeletal muscles in adults is absent in young pups (Richmond et al 2006;Lestyk et al 2009;Shero et al 2012;Geiseler et al 2013). How these differences influence muscle metabolic properties is, at best, poorly understood.…”

“…Adaptations to support such function include high blood O 2 stores (large blood volume, high hematocrit and hemoglobin), large muscle O 2 stores (myoglobin concentrations [Mb] 10-20 times higher than terrestrial, endurance athletes), selective vasoconstriction, bradycardia, and reduced diving metabolic rates (Kooyman and Ponganis 1998;Mottishaw et al 1999;Hochachka and Somero 2002;Butler 2004). Additionally, the locomotory skeletal muscles of adult marine mammals consist primarily of type I (oxidative) and type IID (oxidative-glycolytic) fibers and have high levels of oxidative enzymes, such as CS and HOAD (Reed et al 1994;Kanatous et al 1999Kanatous et al , 2008Polasek et al 2006;Prewitt et al 2010;Shero et al 2012). In general, the muscles of species that dive deeper and/or longer are characterized by higher [Mb], higher aerobic enzyme activities, and a higher percentage of oxidative muscle fibers compared with the muscles of species that make short and/or shallow dives (Kooyman and Ponganis 1998;Noren and Williams 2000;Noren et al 2001;Kanatous et al 2008;Lestyk et al 2009).…”