BOEHM, M.C.*; SECOR, S.M.; University of Alabama, Tuscaloosa; University of Alabama, Tuscaloosa: Energy budget models of specific dynamic action for the amphibians Ambystoma tigrinum and Bufo cognatus

A substantial portion of an ectotherm�s energy expenditure can be attributed to specific dynamic action (SDA), the accumulated energy expended on meal digestion and assimilation. Therefore, an estimate of SDA is an important addition to the construction of an ectotherm�s energy budget. To demonstrate how such estimates can be made, we developed regression models that estimate SDA (kJ) for the salamander, Ambystoma tigrinum, and the toad, Bufo cognatus based on body mass, body temperature, and meal size. Salamanders and toads were each fed cricket meals equivalent in mass to 2.5%, 5%, and 7.5% of their body mass and maintained at three temperatures (15C, 20C, and 25C for A. tigrinum and 20C, 25C, and 30C for B. cognatus). For each meal size�temperature combination (9 data sets), we measured postfeeding oxygen consumption rates from which we calculated SDA. We found meal size, body size and temperature to each contributed significantly to each species� model with meal size explaining most (40 � 50%) of the variation in SDA. Applying field measures of body size and temperature and meal size to these models shall provide accurate estimates of SDA that can be integrated into energy budgets.