The Relationship Between Sex and Aggression in Convict Cichlids (Cichlasoma Nigrofasciatum Günther)

C. nigrofasciatum have been widely used as a preparation in the investigation of aggressive (threat/attack) behavior because of their reputation as a highly aggressive species. They have also frequently been used in studies of learning processes, especially habituation. The reproductive and aggressive behaviors of the family Cichlidae have been described extensively, however, the sexual behavior of C. nigrofasciatum has been treated only cursorily. Several investigators have postulated a mutually inhibitory relationship between sex and aggression such that any decrease in the level of one of these motivational states results in an increase in the level of the other. In order to test this hypothesized relationship between sex and aggression, male and female C. nigrofasciatum were exposed to either male or female stimulus fish for 24 consecutive hours. In the present investigation, performance of sexual behavior was found to inhibit performance of aggressive behavior and vice versa. A principle components statistical analysis was performed in order to reduce the number of dependent variables to a smaller number of underlying clusters of variables referred to as factors. The principle components analysis indicated that the data were characterized by two orthogonal factors, the first of which reflected qualitative differences between the sex and aggression variables, suggesting that a mutually inhibitory relationship exists between sex and aggression. Discriminant analyses indicated that females initiate courtship and perform more aggressive behaviors than males, males elicit more aggression than females, opposite sex dyads perform more sexual behaviors than same sex dyads, and same sex dyads perform more aggressive behaviors than opposite sex dyads. Habituation of aggression was demonstrated in all dyads. Significant decrements in sexual behaviors were not observed.