STEYERMARK, A.C.*; WILSON, K.L.; LEWNO, A.W.; FEGHAHATI, H.S.; OATMAN, K.A.; University of St. Thomas; University of St. Thomas; University of St. Thomas; University of St. Thomas; University of St. Thomas: Mechanistic correlates of among – individual variation in resting metabolic rate

Organisms have a limited amount of energy to allocate to energetic processes such as resting metabolism, activity, growth and reproduction. Thus, subtle differences in energy allocation to one component of the energy budget may affect energy availability to other components. For example, a substantial amount of among�individual variation exists in resting metabolic rate (RMR), which may then lead to fitness differences. This study examines specific mechanisms of among-individual variation in resting metabolism in snapping turtles, Chelydra serpentina. We measured resting carbon dioxide production of turtles in the fall shortly after hatching, and then again in the same turtles in the spring after hibernation. We then sacrificed the animals and removed and weighed their livers, and then measured levels of liver cytochrome c oxidase (COX) and uncoupling protein (UCP). Cytochrome c oxidase catalyzes the transfer of electrons to oxygen and is involved in establishing the proton gradient needed for ATP production. Uncoupling protein acts to modulate the proton gradient across the inner mitochondrial membrane. The establishment and regulation of the proton gradient is energetically expensive and contributes to RMR. First, we examined the repeatability of RMR across an eight month period. Next, we examined correlations between RMR and body mass-corrected liver mass, COX levels, and UCP levels.