Anuran tadpoles are important elements of trophic networks in aquatic environments, being food resource for many types of predators. Thus, the tadpoles exhibit a great variety of defense mechanisms that may be morphological, behavioral and/or physiological. The unpalatability, produced by the accumulation of toxic substances in the skin, is a common mechanism in many frog lineages. However, some predators are not affected by these toxic substances, which may favor the development of alternative mechanisms of defense against predation. In this context, our objective was evaluate if the unpalatable tadpoles of Rhinella ornata (Spix, 1824) may present behavioral mechanisms of defense against predation in the presence of predators that are not affected by toxic substances on its skin. To test our hypothesis, we used two kinds of predators: an aquatic Heteroptera of the genus Belostoma and a dragonfly larva of the genus Aeshna. The tadpoles were located in aquariums with visual and chemical clues of predators (direct risk experiment), only chemical clues (indirect risk experiment) and by the complete absence of predator signals (control). In both cases, the swimming behavior was observed for 5 minutes. During the experiments there was no alteration in swimming behavior of tadpoles.
Predation; unpalatable; defensive behavior; invertebrate predators; chemical signs
