Gustatory control of feeding behavior in goldfish

The present study tests the effects of gustatory quality on feeding behaviors exhibited by goldfish. Goldfish were trained to feed on gelatin pellets, then tested with pellets containing potentially aversive taste stimuli (quinine or caffeine), or mixtures of aversive and appetitive components (amino acids or food). Goldfish feeding includes: initial intake of food particles, a sorting phase consisting of rinsing and backwashing, and a final phase terminating in either rejection or ingestion. Pellets flavored with quinine or caffeine were rejected at concentrations above 10(-5) and 10(-3) M, respectively. Pellets containing a mixture of quinine and ground food or quinine and either L-alanine or L-proline were ingested more frequently than pellets flavored only with quinine. These pellets with mixed chemical components also produced extended sorting behaviors, including prolonged periods of rinsing and backwashing. The prolonged sorting of quinine-food mixtures enabled the animals to separate mechanically the food from the gelatin matrix. These results show that goldfish use chemical cues to drive the intraoral sorting and rejection/ingestion behaviors.