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Nemo through the looking-glass: a commentary on Desjardins & Fernald
Publication . Oliveira, Rui F.; Canario, Adelino V. M.
Castration affects reproductive but not aggressive behavior in a cichlid fish
Publication . Almeida, O. G.; Canario, Adelino V. M.; Oliveira, Rui F.
Gonads are the main source of sex steroids, which have been implicated in the regulation of sexually
differentiated behavior, such as reproductive and aggressive displays. In the Mozambique tilapia
(Oreochromis mossambicus) territorial males have higher androgen levels than non-territorials, express
reproductive behavior and use a urine-borne pheromone to signal their social status towards conspecifics.
Here we investigated the effects of gonadectomy on the circulating levels of androgens and cortisol,
and on the expression of aggressive and reproductive behavior (nest building, courtship behavior, and
nuptial coloration). Males were either castrated, urine bladder damaged, or sham-operated and visually
exposed to a group of females during 8 consecutive days and subsequently to a male on day 9. The urine
bladder damaged treatment was included in the experimental design because a full castration procedure
in this species causes quite often damage to the urine bladder. Gonadectomy lowers dramatically the circulating
levels of androgens measured at 4 and 8 days post-castration and abolishes the expression of
nest building, courtship behavior and nuptial coloration, but has no effect on the expression of aggressive
behavior. These results confirm the gonads as the main source of androgens in this species and show that
androgens are necessary for the expression of reproductive behaviors. However, the expression of aggressive
behavior seems to be decoupled from gonadal steroids, namely androgens, suggesting the action of
independent central mechanisms.
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Fundação para a Ciência e a Tecnologia
Programa de financiamento
3599-PPCDT
Número da atribuição
PTDC/PSI/71811/2006