The role of chemical alarm signals in facilitating learned recognition of novel chemical cues in a coral reef fish

Abstract

Detection and recognition of chemical cues from predators may lower the risk of predation in prey fish. Responses to particular cues in fish may be inherited or learned. In a laboratory experiment, we tested whether the coral-reef-dwelling goby, Asterropteryx semipunctatus, can learn to recognize a novel chemical cue and associate it with danger. Gobies were simultaneously exposed to a neutral chemical cue (the smell of a planktivorous damselfish, Acanthochromis polyacanthus) and either conspecific skin extracts (which contains a chemical alarm cue) or skin extracts from the freshwater swordtail, Xiphophorus helleri. Swordtails, which are allopatric with A. semipunctatus, lack the goby alarm cue and were used to control for a general response to the damaged skin of any fish. Two days after the conditioning, the gobies were exposed to only the neutral chemical cue. Gobies that had been conditioned to the neutral cue paired with conspecific skin extracts on day 1 responded to the neutral cue alone on day 3 with a typical alarm response, including decreased movement and feeding. Gobies that had been conditioned to the neutral cue paired with swordtail skin extracts did not show an alarm response. These results suggest that A. semipunctatus can learn to recognize a novel chemical cue and associate it with danger after a single simultaneous exposure to a novel cue and a conspecific alarm signal. This mechanism of rapid learning of novel chemical cues may be an important way in which coral reef fish learn to recognize predators.