CROSS-SECTIONAL VARIATION IN THE FIBER-TYPE PROFILE OF THE BOTTLENOSE DOLPHIN (TURSIOPS TRUNCATUS) SCALENUS MUSCLE
Brandon Thurow and Jennifer L. Dearolf, Biology Department, Hendrix College, Conway, AR 72032
Many muscles demonstrate variability in their fiber-type profiles (percent slow- and fast-twitch fibers) across their cross-sections. The purpose of this study was to test the hypothesis that the scalenus muscle of bottlenose dolphins (Tursiops truncatus) would also exhibit cross-sectional variability in its fiber-type profile. To test this hypothesis, we took five samples from different regions across the cross-section of one dolphin scalenus muscle and stained sections from these samples for their myosin ATPase activities and metabolic enzyme levels. The enzymes investigated included two oxidative enzymes [succinic dehydrogenase (SDH) and nicatinamide adenine dinucleotide tetrazoleum reductase (NADH-TR)] and one glycolytic enzyme [alpha-glycerophosphate dehydrogenase (GPD)]. Myoglobin levels in each of the samples were also measured. We found a large amount of variability between the samples in fiber-type profile (44% - 64% fast-twitch fibers). There were also differences in the levels of the metabolic enzymes and myoglobin concentrations (1.23 - 2.64 g myoglobin/100 g muscle) between samples. These findings support our hypothesis and suggest that a single sample from the scalenus muscle in bottlenose dolphins is not sufficient to characterize the fiber-type profile of the entire muscle.
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