FORMATION OF THE SELFISH SCHOOL

Mutualistic defense of cichlid and catfish young by their parents was examined by remote underwater video cameras in Lake Malawi, Africa. Two species of cichlid, Ctenopharynx pictus and Copadichromis pleurostigmoides placed their young into catfish, Bagrus meridionalis, nests and defended the broods for up to three weeks. Cichlid young were forced to the periphery of the school by the biparental catfish. Eighty-seven percent of predatory attacks on mixed broods were directed towards the cichlids on the outside of the school. Rate of attack upon pure catfish broods was seven times higher than on catfish in mixed broods. Catfish appeared to encourage a mutualistic relationship by allowing the young cichlids, away from the school, to feed upon their skin. The findings support the predation dilution and geometrical design hypotheses of the selfish school model previously proposed by McKaye & Oliver (1980).