P1.159 Wednesday, Jan. 4 A comparative study of the locomotor muscle of extreme deep-diving cetaceans VELTEN, B P*; MCLELLAN, W A; PABST, D A; Univ. of North Carolina, Wilmington; Univ. of North Carolina, Wilmington; Univ. of North Carolina, Wilmington firstname.lastname@example.org
Deep-diving marine mammals exhibit adaptations to increase their oxygen storage capabilities and prolong aerobic metabolism during a dive. These adaptations include high levels of myoglobin and low mitochondrial volume densities (MVD) within locomotor muscles. Most studies to date have examined the muscle physiology of deep-diving pinnipeds, with few studies focusing on cetaceans. Recent tagging data demonstrate that short-finned pilot whales (Globicephala macrorhynchus) are deep divers that can perform high-speed sprints deep within their dives (Soto et al., 2008). Beaked whales (e.g Mesoplodon densirostris and Ziphius cavirostris) are currently thought to perform, on average, the longest and deepest dives of any air-breathing vertebrate (50-60 min and 800-1000 m) (Tyack et al., 2006). We propose to examine the locomotor muscles of these extreme divers. Assays will be performed on an epaxial locomotor muscle (m. longissimus) collected from stranded animals (G. macrorhynchus, n=6; Ziphiids, n=6). Myoglobin concentration will be measured to determine the oxygen storage capability of the axial locomotor muscles. Muscle fiber profiles will be determined and used as an indicator of the metabolic pathways used to fuel muscle contraction. Using transmission electron microscopy, MVD will be measured as an indicator of the muscle’s rate of oxygen consumption. Muscle buffering capacity will be measured to determine if these animals exhibit enhanced abilities to cope with an increased reliance on anaerobic metabolism during a dive. We hypothesize these species will exhibit adaptations to prolong their aerobic dive duration through high myoglobin concentrations and low MVD. However, the extreme nature of their dives may also require enhanced anaerobic capabilities and result in high muscle buffering capacities.