Morphological and Developmental Responses of Anuran Larvae (Physalaemus albonotatus) to Chemical Cues from the Predators Moenkhausia dichoroura (Characiformes: Characidae) and Belostoma elongatum (Hemiptera: Belostomatidae)

Abstract

Animals constantly face various predators in diverse environments. The phenotypic changes induced in prey by different predators may differ quantitatively but not qualitatively, possibly because similar defense strategies are effective against different predators. Also, species inhabiting more-permanent habitats tend to exhibit defense strategies that enable them to coexist with potential predators. We examined phenotypic plasticity responses to different predators. We tested differences in the morphology and growth rates of mewing frog Physalaemus albonotatus tadpoles raised in the presence of chemical cues from water-bug (Belostoma elongatum) and fish (Moenkhausia dichroura) in order to determine if this species has generalized or specialized responses to different predators. The experiment was performed under microcosm conditions, and the experimental design consisted of 3 treatments: chemical cues from fish and from water-bug, and a control group. Each container held a single larva in order to obtain independent data for different variables. Each treatment was replicated 30 times, with 90 total experimental units. The main findings were as follows: 1) tadpole morphology was significantly affected by the presence of predator cues; 2) tadpoles reared with fish cues were significantly larger than those subjected to the other 2 treatments (water-bug cues and the control), while those reared with water-bug cues were also larger than the control; and 3) tadpoles exposed to chemical cues of predators exhibited accelerated growth rates and development stages. Our results suggest that the presence of predaceous fish and water-bug has a major effect on morphology, growth rate, and development of P. albonotatus tadpoles. Morphological variables, growth rates, and developmental stages followed the same pattern, and all of these variables showed increases in tadpoles exposed to chemical cues of predators, possibly because P. albonotatus larvae develop in temporary and semi-permanent ponds and are able to exploit different habitats, and therefore their responses to chemical cues from different predators are similar.