Intragroup behavioural changes and the initiation of sex reversal in a coral reef fish in the laboratory

Abstract

Observations of the coral reef fish Anthias squamipinnis (Peters) suggest that the behavioural control of female-to-male sex reversal is more complex than a simple dependence on the presence or absence of a male or on simple aspects of aggression or aggressive dominance. When the behavioural interactions of all group members of small, bisexual social groups of this fish were examined before and after male removal, two behavioural features were identified as possible factors controlling the initiation of sex change: the profile for behaviours received from, and the percentage of rushes given to other group members. Males and females each showed characteristic profiles both for behaviours given and for behaviours received. On the basis of the behaviour-given profile I identified two types of female. Both types were capable of changing sex following the removal of the male. Two to four weeks were required by sex-reversing fish for the profiles for behaviour given to change to a completely male form. After male removal, the remaining females began to treat the sex-reversing fish as though she the behavioural and coloration changes of sex reversal in a female.