Meeting Abstract
Predation risk can strongly influence the growth and development of organisms. In anurans, predators can depress larval growth rates and induce changes in morphology. For some species, increases in tail size can improve larval escape rates but come at the cost of decreased gut length and digestive efficiency. In red-eyed treefrogs, Agalychnis callidryas, highly competitive, low resource environments induce longer guts and shorter tails. In this study, we evaluated the net effect of combining a larval predator and a low resource environment. At the Smithsonian Tropical Research Institute in Gamboa, Panama, we reared A. callidryas larvae in 400 L mescocosms with and without a caged Belostomatid predator. Predators were fed two A. callidryas hatchings every other day to generate kairomones in the larval environment. Larvae were maintained at 25 individuals per mesocosm, a density known to produce a competitive environment and induce longer guts. Larval growth was highly variable among tanks and did not vary significantly with predator treatment. Food availability may have limited larval growth to such an extent that further predator effects were not possible. Predators did induce small but significant increases in larval tail length. However, there were no associated changes in gut length. These morphological results suggest that when faced with simultaneous stressors of food limitation and predation, larvae adopt a morphology that allows for modest increases in tail size without sacrificing digestive efficiency. Additional studies are needed with higher food resources and varying rates of predation pressure to better understand these tradeoffs.
