Meeting Abstract
Toothed whales use a specialized nasal system to produce vocalizations that they use to navigate and communicate. For example, the Atlantic bottlenose dolphin (Tursiops truncatus) uses its primarily slow-twitch left nasal musculature (LNM) to produce whistles, while its right nasal musculature (RNM) produces clicks using fast-twitch fibers. In comparison, the harbor porpoise (Phocoena phocoena) only emits clicks, and its LNM and RNM are both primarily fast-twitch. Thus, we hypothesized that the dolphin RNM would have higher glycolytic activity than its LNM and both porpoise musculatures would have similar glycolytic activities. To test these hypotheses, samples of the LNM and RNM of dolphins and porpoises were collected from stranded animals and frozen. The muscle samples were prepared for the lactate dehydrogenase (LDH) assay, and their LDH activities were assayed under the following conditions: 50 mM imidazole, 0.15 mM NADH, 1 mM pyruvate, and pH 7.0 at 37oC. Using a microplate reader, we measured the rate of change in absorbance (340 nm) at Vmax to calculate glycolytic activity. One specimen per muscle of each species was used to determine the optimum dilution factor before running that dilution factor on all specimens. T. truncatus RNM glycolytic activity was found to be 207.4 (± 95.2) μmol /min*g, while the LNM activity was 172.9 (± 12.6) μmol /min*g. P. phocoena equivalents were 266.9 (± 205.4) and 215.7 (± 105.7) μmol /min*g. Results showed higher glycolytic activity in the RNM than in the LNM for both species and higher glycolytic activity in porpoise muscles compared to the dolphin equivalents. However, all four of the measured glycolytic enzyme activities were low, which fits with the small energy requirements of clicking in these cetaceans.
