Olfactory cues that indicate predation risk elicit a number of defensive behaviors in fishes, but whether they are sufficientto also induce morphological defenses has received little attention. Cichlids are characterized by a high level of morphologicalplasticity during development, and the few species that have been tested do exhibit defensive behaviors when exposed toalarm cues released from the damaged skin of conspecifics. We utilized young juvenile Nicaragua cichlids Hypsophrys nicaraguensisto test if the perception of predation risk from alarm cue (conspecific skin extract) alone induces an increased relativebody depth which is a defense against gape-limited predators. After two weeks of exposure, siblings that were exposed to conspecificalarm cue increased their relative body depth nearly double the amount of those exposed to distilled water (control) andzebrafish Danio rerio alarm cue. We repeated our measurements over the last two weeks (12 and 14) of cue exposure when thefish were late-stage juveniles to test if the rate of increase was sustained; there were no differences in final dimensions betweenthe three treatments. Our results show that 1) the Nicaragua cichlid has an innate response to conspecific alarm cue which is not ageneralized response to an injured fish, and 2) this innate recognition ultimately results in developing a deeper body at a stage ofthe life history where predation risk is
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