Learned Recognition by Zebrafish and Other Cyprinids

Antipredator behavior is triggered by a combination of internal proximate mechanisms (anatomical receptors and the physiological processes that regulate their function) and external environmental cues that signal the context and timing of when behavior is likely to be effective. Responses to some external environmental triggers, such as the presence of conspecific chemical alarm cue, are governed strictly by genetic templates. Other external environmental triggers are learned through a special type of associative learning called releaser-induced recognition learning. Zebrafish are one of several model systems upon which this body of literature has been developed. Minnows (including zebrafish) associate danger with any novel stimulus (visual, chemical, or auditory) that is correlated with the presence of chemical alarm cue released from damaged epithelial tissue of conspecifics. Alarm cue is released only in the context of predation and serves as a reliable external environmental trigger for associating novel stimuli with predation risk. Minnows use learned recognition to learn about predator identity and about the chemical alarm cues of ecologically similar heterospecifics. Learning also occurs when alarm cues are released indirectly through the digestive tract of the predator. Behavioral and chemical responses to disturbance can also facilitate learned recognition. Learned recognition is an ideal system with which to study the molecular mechanisms that underlie the cognitive processes of learning and memory. Collectively, this suggests that zebrafish are a very promising model organism for future study.