Visual and chemical release of feeding behavior in adult rainbow trout.

Feeding behavior of adult rainbow trout (Oncorhynchus mykiss) is released by visual and/or chemical stimuli. Detection of either a conditioned visual or a conditioned chemical stimulus creates an excitatory feeding state within the central nervous system which turns on feeding behavior composed of swimming, turning and biting/snapping actions. Particular amino acids that are highly effective physiological taste stimuli that are also detected through olfaction (e.g. L-proline, L-alanine, L-leucine) release the initial sequence of food searching and biting/snapping behaviors; however, an effective olfactory, but poor gustatory, stimulus (e.g. L-arginine) is rarely effective behaviorally. After bilateral removal of the paired olfactory organs, visual stimuli alone release the entire set of feeding behavior patterns. Since amino acids that are highly potent physiological taste stimuli do not release either feeding behavior or reflex biting/snapping actions in adult anosmic rainbow trout, it is postulated that the olfactory system detects potent taste stimuli and provides the afferent input for arousal and the release of all feeding activity patterns.