Meeting Abstract
P2.135 Monday, Jan. 5 A Comparative Study of the Capacity for Aerobic Metabolism in the Locomotor Muscle of the Three Species of Thresher Shark (Family Alopidae). PATTERSON, J.P.*; BERNAL, D.; SEPULVEDA, C.; University of Massachusetts Dartmouth; University of Massachusetts Dartmouth; Pfleger Institute of Environmental Research Jpatterson1@umassd.edu
A recent study of the three species of thresher shark (Family Alopidae) has revealed some striking interspecific differences in locomotor muscle morphology. The common thresher (Alopias vulpinus) differs significantly in the position of the red myotomal muscle (RM) when compared to the bigeye (A. superciliosis) and the pelagic thresher (A. pelagicus), and is the only species showing regional muscle endothermy. Due to the endothermic nature of the common thresher, it is hypothesized that the locomotor muscle of this species will have a higher capacity for aerobic metabolism at 20C relative to the other two species. The purpose of this study was to compare the activity of citrate synthase (CS; an index of aerobic capacity), and lactate dehydrogenase (LDH; an index of anaerobic capacity) in the RM of three species of thresher. Temperature readings were also taken in six longitudinal positions along the body of the sharks, with a temperatures taken every centimeter of probe penetration. Temperature readings for the common thresher were above that of the ambient temperature at the depth caught, while the pelagic and bigeye body temperatures were closer to that of the ambient temperature at depth caught. The CS and LDH activity in the RM of the common thresher at 20C was 2.4 and1.3 times higher respectively when compared to the other two species. The average Q10 between 15-25C (1.65-CS, 1.64-LDH) in the common thresher did not differ significantly from that of the pelagic and bigeye. These results indicate that although the thermal effect on enzyme activity is similar, the overall activity of both these enzymes in the RM is higher for the common thresher shark.
