Anti-predator response of naive and experienced common bully to chemical alarm cues

Histological analysis of the skin of common bully Gobiomorphus cotidianus, a New Zealand native eleotrid fish, revealed the presence of club cells in the epidermis. Epidermal club cells are frequently associated with the production of alarm substance (Schreckstoff). The behavioural responses of perch-naive and perch-experienced common bullies to either conspecific skin extract or chemical cues from an introduced predator, perch Perca fluviatilis, were then examined. Both perch-naive and perch-experienced common bullies exhibited a behavioural response when exposed to conspecific skin extract, indicating the probable presence of an alarm substance. In contrast, only perch-experienced common bullies recognized and exhibited a subsequent behavioural response to the odour of perch. This study is the first to document the presence of epidermal club cells and a behavioural response to a conspecific chemical alarm signal for fishes in the Eleotridae. The results indicate that common bully can learn to recognize perch odour as a threat, and that this ability may be a result of previous predator labelling involving a conspecific alarm substance. (C) 2004 The Fisheries Society of the British Isles.