Hormones and social behavior of cichlid fishes: a case study in the Mozambique tilapia

Oliveira, Rui Filipe; Canário, Adelino V. M.

http://hdl.handle.net/10400.12/1336

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Authors

Oliveira, Rui Filipe

Canário, Adelino V. M.

Abstract(s)

The Mozambique tilapia, Oreachrzlrnis rnossambicus, is used as a case study to illustrate different aspects of the relationship between androgens and social behavior in cichlid fish. First the mating system of 0. mossambicus and its variations is described, namely the occurrence of alternative male mating tactics and male-male courtship, and the influence of social status on mating decisions and mating success. A discussion of a two-way causal relationship between androgens and social behavior follows, including the implications of social modulation of androgens for the expression of androgen-dependent male displaying characters (i.e. differential expression of secondary sex characters and male social behavior according to social status). The mechanisms regulating the action of androgens upon male behavior are also discussed with original data on the activity of brain aromatase. It is shown that male 0 . mossambicus have higher levels of brain aromatase activity than females, but aromatase activity is related neither to the gonadosomatic index nor to social status. In contrast, an androgen environment with predominance of the non-aromatizable androgen 1 1 -ketotestosterone over the aromatizable testosterone is indicative of high social status and territorial possession. This suggests that 1 1 -ketotestosterone may be playing a major role in the expression of male characters, both behavioral and morphological. The role of testosterone in female aggression is also discussed. An association between female aggression and plasma testosterone was found during the mouthbrooding cycle. Finally, the relevance of cichlids for comparative studies of vertebrate behavioral endocrinology is highlighted.