Diving physiology in marine mammals : significant findings in pinniped muscle physiology and trachea morphology.
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Moore, Colby D.
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The muscular biochemistry and respiratory morphology of diving mammals are closely intertwined through the utilization and allocation of inspired oxygen for metabolism. Marine mammal physiological mechanisms and adaptations are of great intrigue due to the heightened environmental pressures that these animals are routinely subjected. These species also experience varying degrees of ischemia, hypoxemia and gas tissue saturation, which are pathological in terrestrial mammals. Data included in this dissertation suggest a unique skeletal muscle fiber type profile for the deep-diving Northern elephant seal; a profile predominately comprised of enlarged aerobic type I myofibers. In addition, enzymatic data suggest that diving mammals maintain higher levels of aerobic enzymes in primary locomotory muscle and that muscle-based enzymes degrade rapidly and variably with temperature and time. Histological analysis of harbor seal tracheal rings microscopically describes a unique continuity of cartilage that correlates with lung compression, depth at which lungs collapse, as well as maximum dive depth. Cumulatively, biochemical and structural adaptations allow diving mammals to reach extensive depth, while maintaining homeostatic levels of on-board gasses and avoiding dive-related injury. Ultimately, this research highlights the relationship between morphology, physiology and life history of these animals.