Meeting Abstract

P3.69  Monday, Jan. 6 15:30  Variation in organ and tissue mass loss during fasting for the snake Nerodia rhombifer LARKIN, M.*; SECOR, S.M.; Univ. of Alabama; Univ. of Alabama mlarkin@crimson.ua.edu

Fasting related loss in body mass stems from the cumulative loss of mass of individual tissues and organs. However, not all organs and tissues lose mass at the same rate resulting in variation among organs in the reduction of mass with fasting. Tissues that provide a source of energy and are not essential for performance during fasting (e.g., fat bodies) would predictably be depleted at a faster rate than organs that still need to maintain performance during the fast. In addition, individuals may vary in the rate of organ loss during fasting as a function of differences in metabolic expenditure and the allocation of endogenous energy. We examined individual variation in the loss of body and organ mass with fasting for the diamondback watersnake (Nerodia rhombifer). We obtained baseline measures of body and organ masses from ten snakes immediately after their capture. For the next six months we dissected five snakes each month to assess the reduction in body and organ masses from fasting. For the first three months of fasting, snakes lost body mass at an average rate of 1.3 g/day, thereafter mass loss continued at 0.3 g/day. Relative to the loss of body mass, we found that the fat bodies, liver, pancreas, small intestine, and kidneys lost mass at a greater rate. Muscle, heart, lung, and skin lost mass at a rate equal to or less than that of body mass loss. As expected fat and organs associated with digestion lose relatively more mass with fasting than organs necessary for day to day survival. We found considerable variation in fasting loss of body fat after 6 months, ranging from 25-100% depletion. Watersnakes in this population exhibit variation in standard metabolic rate independent of body mass, suggesting that individual variation in SMR explains, in part, the variation in body fat loss.