P1.71 Jan. 4 Tail-Flipping in Crustaceans: A Model for Muscle Metabolic Design JIMENEZ, A.G.*; KINSEY, S.T.; University of North Carolina Wilmington; University of North Carolina Wilmington email@example.com
We examined the relationship between the scaling with body mass of metabolic rate (O2 consumption) and the scaling of a metabolic process (arginine phosphate re-synthesis) following tail-flipping responses in crustaceans. Four species of tail-flipping crustaceans were examined Panulirus argus, Peneaus duorarum, Peneaus aztecus and Palaemonetes pugio. Crustacean anaerobic muscle fibers often grow hypertrophically and we hypothesized that fiber diameter would increase with body mass so that large animals have large fibers. Further, we expected that SA:V and diffusion constraints associated with large fiber size would hinder post-tail flip aerobic recovery, leading to an uncoupling of the scaling of O2 consumption and AP re-synthesis. Abdominal muscle fiber size was measured using light microscopy. Post-tail flip oxygen consumption was measured as an indicator of aerobic metabolic rate using closed-chamber respirometry. Oxygen consumption of the tail muscle was assessed using the whole animal because the abdominal musculature dominates whole animal energetics during and after a tail-flip. The rate of metabolic re-synthesis of arginine phosphate following burst contraction was measured using 31P NMR spectroscopy. Muscle fiber size was larger in larger animals, exceeding 200µm in the largest P. argus. The body mass scaling exponent, b, for O2 consumption (b=-0.2569) was not similar to that for the initial rate of AP re-synthesis (b=-0.0292). It therefore follows that the P:O ratio (μmoles of AP synthesized per μliter of oxygen consumed post tail-flipping) increases with body mass. This 10-fold difference in the scaling exponents may be due to an increased reliance on anaerobic recovery as the animals’ size increases, which may be due to SA:V and intracellular diffusion constraints in large fibers.