A re-evaluation of the effect of shoalmate familiarity on the proliferation of alarm substance cells in ostariophysan fishes

A re-examination of data from Wisenden & Smith Journal of Fish Biology 50, 799-808) suggests that fathead minnows Pimephales promelas adjust investment into epidermal alarm substance cells (ASC) facultatively based upon the level of perceived risk. When placed into a container with non-familiar shoalmates (relatively high risk) ASC production increased. This allows these individuals to attract a secondary predator better. When placed into a container with familiar shoalmates (relatively low risk) ASC production decreased. This may reflect increased effectiveness of a group antipredator response by familiar individuals, and/or the cost to inclusive fitness of attracting additional predators to the vicinity of their kin. (C) 1998 The Fisheries Society of the British Isles.