Meeting Abstract
A variety of organisms exhibit metabolic plasticity in response to environmental conditions during development, but few studies have considered its importance in amphibians. In the red-eyed treefrog, Agalychnis callidryas, larvae reared in competitive environments with low food resources have smaller livers and longer guts than those reared in resource-rich environments. Although these larvae have large gut capacities, they continue to feed at low levels even when ad libitum food becomes available. The purpose of this study was to determine if differences in organ size and intake patterns are associated with differences in metabolism induced by the larval environment. We also examined the effect of larval predation risk on metabolism because other studies indicate this could be an important determinant of larval metabolism. We reared larvae in two sets of outdoor mesocosms at the Smithsonian Tropical Research Institute in Gamboa, Panama. In the first set of mesocosms, larvae were maintained at low and high densities (5 or 45 larvae per mesocosm, respectively) with a standard amount of food and different per capita resources. In the second set of mesocosms, larvae were reared at an intermediate density (25 larvae per mesocosm) with and without a caged Belostomatid predator. Predators were fed two A. callidryas hatchlings every other day for kairomone production in the mesocosm. Once larvae reached a standard size of aprox 3cm in length, we measured standard metabolic rate (SMR) with closed-system respirometry. As predicted, larvae raised in low resource environments had lower metabolic rates than those reared with high resources, explaining previously reported intake patterns. Metabolic rate did not vary with predation, but additional studies in which more kairomones are generated may be warranted.
