Sensory basis of food detection in tadpoles of Polypedates maculatus (Anura: Rhacophoridae): an experimental approach

Abstract

The mechanism of food detection in tadpoles of Polypedates maculatus was experimentally tested. We used a rectangular glass test tank with stimulus zones in opposite ends to provide visual and/or chemical food. For visual cues, boiled spinach was placed inside a glass container, and for chemical cues boiled spinach was placed in a mesh cage. Each tadpole of P. maculatus (either at an early or medium developmental stage) was held at the center of the test tank for acclimation. The tadpole was released, and we recorded whether it approached or did not approach the caged food. Tadpoles of all stages failed to detect food using visual cues. Tadpoles of all stages detected food using chemical cues. In tests using chemical cues, they spent the majority of their time (69.3% by early stage tadpoles and 87.3% by medium-stage tadpoles) near the container with food than in the end with no containers or with only visual food cues. Tadpoles in medium stages spent more time near food (18.1% of total time) than tadpoles in early stages. These findings indicate that tadpoles of P. maculatus detect food by chemical sensory mechanisms rather than visual ones. Tadpoles in medium stages spent more time near food than tadpoles in early stages indicating that time spent foraging increases as tadpoles grow.