Meeting Abstract
Amphibian larvae exhibit a high amount of developmental plasticity in response to variable environments. In this study, we examined the effects of competition and predation threat on metabolism and organ size plasticity in red-eyed treefrogs (Agalychnis callidryas). Larvae were reared at high and low density in 30 L outdoor tanks at the edge of the rainforest (N = 14 tanks per density) at the Smithsonian Tropical Research Institute in Gamboa, Panama. Half of tanks within each density (N = 7) contained a caged Belostomatid predator and half did not (N = 7). Each predator was fed A. callidryas hatchlings daily to facilitate the release of kairomones into the tanks. There were significant negative effects of both density and predation on larval growth. The metabolic rates of larvae reared at low density were twice as high as those reared at high density. These metabolic rates were associated with significantly heavier livers, pancreases and brains. There was also a much smaller, yet significant, negative effect of predation on metabolic rate. Predation also induced slightly heavier brains, but had no effect on liver or pancreas size. Differences in metabolic rate may be attributed to organ size plasticity. Additional analyses will include more detailed measurements of brain anatomy and tail morphology.
