Effect of hunger on the response to, and the production of, chemical alarm cues in a coral reef fish

Abstract

A wide variety of fish species release chemical alarm cues upon mechanical damage to their skin by predator attack. We investigated the effects of short-term food deprivation on the response to, and the production of, chemical alarm cues in the coral reef-dwelling goby Asterropteryx semipunctatus (family Gobiidae). Gobies deprived of food for 4 days did not react with fright when exposed to conspecific skin extracts. However, when the same individuals had been fed ad libitum, they responded with a typical alarm reaction to the skin extracts, including decreased movement and feeding. In a second experiment, gobies were exposed to skin extracts from conspecifics that had been food deprived and from conspecifics fed ad libitum. Damaged skin from food-deprived individuals did not elicit an alarm response in conspecifics, whereas skin from individuals that had been fed ad libitum yielded a typical alarm response. Histological sections of goby skin showed that food-deprived gobies had fewer sacciform cells in their epidermis than did gobies fed ad libitum. Evidence suggests that there may be a trade-off between foraging and antipredator behaviour, and also between the benefits derived from maintaining chemical alarm cue cells and the cost of producing them in A. semipunctatus.