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 ofeither a conditioned visual or a conditioned chemical stimuluscreates an excitatory feeding state within the central nervoussystem which turns on feeding behavior composed of swimming,turning and biting/snapping actions. Particular amino acidsthat are highly effective physiological taste stimuli that arealso detected through olfaction (e.g. L-proline, L-alanine,L-leucine) release the initial sequence of food searching andbiting/snapping behaviors; however, an effective olfactory,but poor gustatory, stimulus (e.g. L-arginine) is rarely effectivebehaviorally. After bilateral removal of the paired olfactoryorgans, visual stimuli alone release the entire set of feedingbehavior patterns. Since amino acids that are highly potentphysiological taste stimuli do not release either feeding behavioror reflex biting/snapping actions in adult anosmic rainbow trout,it is postulated that the olfactory system detects potent tastestimuli and provides the afferent input for arousal and therelease of all feeding activity patterns. Chem. Senses 22: 375–382,1997.