Kin recognition and inbreeding avoidance in zebrafish, Danio rerio, is based on phenotype matching

Differentiating kin from nonkin enables organisms of many species to allocate resources or altruistic behaviour towards related conspecifics and to avoid mating with close relatives. Kin recognition mechanisms can vary among species and may reflect the social environment. Learned familiarity with nest or shoalmates may serve as a good indication that individuals are related, as long as the social system is sufficiently stable to avoid intermingling of unrelated individuals with siblings. Phenotype matching allows for recognition of even unfamiliar kin because individuals establish an olfactory, visual or acoustic template for their kin during early development and compare this template to cues from unfamiliar individuals later in life. We tested which kin recognition mechanism is used by zebrafish and we found that the preference for kin changes with sexual maturity. The olfactory preference of laboratory-bred juveniles and reproductively active adults were tested in an odour choice flume. juveniles of mixed-sex groups spent more time on the side of unfamiliar kin than unfamiliar nonkin, indicating that kin recognition and preference are based on a phenotype matching mechanism. They also preferred familiar kin to unfamiliar kin, showing that familiarity with individuals enhances kin preference. Preference changed with sexual maturity. Adult females preferred the odour of unfamiliar, unrelated males to unfamiliar brothers, indicating inbreeding avoidance. Adult male zebrafish showed no preference for the odour of related or unrelated females. To our knowledge, this is the first study testing different kin recognition mechanisms and switching of kin preference in the same species of fish. (c) 2006 The Association for the Study of Animal Behaviour Published by Elsevier Ltd. All rights reserved.