Behavioural changes of protogynous sex reversal in a coral reef fish in the laboratory

Abstract

In the group-living, protogynous coral reef fish Anthias squamipinnis (Peters), males differed from females behaviourally by performing and reveiving five movement patterns at different rates. Following removal of a male from laboratory social groups, one female changed sex. As sex reversal proceeded, the sex-reversing female progressively increased the rate of performance and reception of those behaviours distinguishing the sexes. Nose rushes increased in rate beginning 2 days after male removal. U-swims and third-dorsal-spine erections began to increase 4 and 11 days, respectively, after male removal. Three to four weeks were needed for the sex-changing fish to perform these behaviours at the full male rate. An analysis of behavioural rates for all individuals in the social group before and after male removal revealed that the behavioural changes of sex reversal were displayed only by one female in the group and did not occur in control groups. A full description is provided of movement patterns, and analogies drawn between the development of U-swims by the adult sex-changing fish and the behavioural ontogeny of juveniles in other species.