SEX-ROLE DIFFERENTIATION IN FEEDING AND DEFENSE OF YOUNG BY A BIPARENTAL CATFISH, BAGRUS-MERIDIONALIS

Parental feeding of young is well documented among endothermic vertebr ates and social insects but is rare among fish. Bagrus meridionalis pa rents feed their young in a manner analogous to birds and social insec ts. Females feed trophic eggs to the young and the male burrows to exp ose benthic invertebrates for the young to eat. These behaviour patter ns and parental defence of the young were directly observed with remot e video-cameras. Division of labour between parents exists not only in the feeding of the young but also in their defence. Role differentiat ion in defence of the young was greatest when the young were subjected to the most attacks from predators. The female attacked and chased po tential brood predators at the edge of the school while the male remai ned with the brood, executing more frontal displays. On the other hand , as the young grew older and predation decreased, both parents engage d in more sex-specific food provisioning behaviour such as egg release by the female and nest burrowing by the male. Parental role different iation and monogamy in this species might have evolved both to enhance the growth rate of the young and to reduce their susceptibility to pr edation.