Sensory basis of food perception in tadpoles of the frog, Sphaerotheca breviceps

Abstract

The mechanism of food detection was studied in tadpoles of the frog Sphaerotheca breviceps using a rectangular glass tank, the two ends of which served as stimulus zones and housed the food (boiled spinach), providing either visual (food inside a glass beaker) or chemical (food inside a mesh cage wrapped with cheese cloth) cues or both. Each test tadpole (starved for 24 h before the trials) was placed in a centrally kept mesh cage for 5 min to enable perception of food cues. Each trial lasted for 10 min and the time spent by test tadpoles in each stimulus zone was recorded. The tadpoles showed no bias towards any particular side of the apparatus or trial procedure (end bias tests). In tests with visual cues at one end of the test tank also, the tadpoles moved randomly as in end bias tests. In contrast, in tests with chemical cues in one stimulus zone, the tadpoles spent majority of their time near chemical cues of food rather than in the zone that was chemically blank or provided only visual cues. In tests with food in open space in one zone and in the mesh cage in the opposite zone (both providing water-borne chemical cues), the tadpole distribution was random. The findings thus show that S. breviceps tadpoles detect food by chemical sensory mechanism rather than visual ones.