Meeting Abstract

P2.89  Wednesday, Jan. 5  Locomotor muscle profiles of cetaceans: A comparison of deep- vs. shallow-diving cetaceans KIELHORN, C.E.*; MCLELLAN, W.A.; PABST, D.A.; University of North Carolina Wilmington cek9230@uncw.edu

It is hypothesized that marine mammals normally dive within their aerobic dive limit (ADL), which is dependent, in part, on skeletal muscle myoglobin content, mitochondrial volume density (MVD), and fiber type and size. These characters have been studied in pinniped species with varied dive behaviors. Muscles of short duration, shallow divers display high myoglobin content, enhanced MVD, mixed fiber composition and relatively small fiber diameters; muscles of a long duration, deep diver display higher myoglobin content, reduced MVD, and large, predominately slow oxidative fibers (Kanatous et al., 1999, 2002). These modifications may contribute to the extended ADL of deep-diving pinnipeds. While data on muscle myoglobin content and fiber type exist for some cetaceans, this study is the first to examine all these variables across taxa with distinctly different dive regimes. The aim of this study is to evaluate the longissimus muscle of a short duration, shallow diver (bottlenose dolphin, Tursiops truncatus), and a long duration, deep diver (pygmy sperm whale, Kogia breviceps). We hypothesize that locomotor muscle from T. truncatus and K. breviceps will vary in a manner similar to that observed in diving pinnipeds. Using electron microscopy, histo- and biochemical techniques, we are determining myogobin content, MVD, and muscle fiber type and size, of samples collected from stranded individuals. Preliminary data demonstrate that, contrary to long duration deep-diving pinnipeds, the muscle of the K. breviceps displays slow oxidative and fast glycolytic fibers; the diameters of these fibers are approximately 1.5 times larger than those of T. truncatus, across fiber types. This poster will present results on muscle fiber type, size and myoglobin concentration.