Monogamy and sex change by aggressive dominance in coral reef fish

Abstract

IN several sequentially hermaphroditic coral reef fish, of which individuals first function as females and then males (protogynous hermaphroditism), dominant males can control production of other males by aggressive dominance over females^1–4. Robertson suggested that socially controlled protogynous sex changes might operate only in species with a well defined polygynous social system “based on individual relationships”^2,3. Further exogenous and endogenous factors may control sex change in species which school anonymously and in which the individuals lack special individual relationships. We describe here socially controlled proteandric hermaphroditism (individuals functioning first as males and then as females) in the anemone fish Amphiprion, in which females control production of females by aggressive dominance over males.