The effect of chemical signal of predatory fish and water bug on the morphology and development of Elachistocleis bicolor tadpoles (Anura: Microhylidae)

Abstract

Changes in environmental conditions can induce organisms to alter their morphology, behavior and life history. Predation is an important factor in many aquatic communities and can strongly select for anti-predator responses. In the present work, we examined the responses in morphology, growth rate and development rate of Elachistocleis bicolor tadpoles raised in the presence of chemical cues from two different predators: a water bug (Belostoma elongatum) and a fish (Moenkausia dichroura). The experiment was performed in microcosm conditions. The experimental design consisted of three treatments: chemical cues from fish, cues from water bugs and a control group. Each treatment was replicated 30 times. Each container held a single larva. The main results were: (1) there were significant differences in body depth between the predator treatments (fish vs. water bug) and between the control group and the water bug treatment, (2) there were significant differences in tail depth between predator treatments (fish vs. water bug) and between the control group and the fish treatment, (3) there were no significant differences in the growth rate and developmental rate among the treatments. Our results suggest that the presence of predaceous fish and water bugs cause different effects on tadpole morphology. In the presence of water bugs, tadpoles decreased body depth, whereas in the presence of fish tadpoles increased tail depth. These responses could be related to the way in which predators capture their prey. Predator chemical cues did not have any detectable effect on the growth rate and development rate of E. bicolor tadpoles.