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Castration affects reproductive but not aggressive behavior in a cichlid fish
Olinda Almeida1, Adelino V M Canário2, Rui F Oliveira3
1Unidade de Investigação em Eco-Etologia, ISPA - Instituto Universitário, Rua Jardim do Tabaco, 34, 1149-041 Lisboa, Portugal.
General and Comparative Endocrinology
|April 1, 2014
Summary
Gonadectomy in Mozambique tilapia significantly reduced androgen levels and eliminated reproductive behaviors like courtship and nest building. Aggressive behavior, however, remained unaffected, suggesting independent regulation.
Area of Science:
- Endocrinology
- Behavioral Ecology
- Neuroscience
Background:
- Sex steroids from gonads regulate sexually differentiated behaviors.
- Mozambique tilapia males exhibit higher androgens and reproductive behaviors, using pheromones for social signaling.
Purpose of the Study:
- To investigate the effects of gonadectomy on androgen and cortisol levels.
- To assess the impact of gonadectomy on aggressive and reproductive behaviors in male Mozambique tilapia.
Main Methods:
- Male Mozambique tilapia underwent castration, urine bladder damage, or sham surgery.
- Fish were exposed to females for 8 days, followed by exposure to a male on day 9.
- Circulating androgen and cortisol levels were measured, alongside behavioral observations.
Main Results:
- Gonadectomy drastically reduced circulating androgen levels.
- Reproductive behaviors (nest building, courtship, nuptial coloration) were abolished post-gonadectomy.
- Aggressive behavior was not affected by gonadectomy.
Conclusions:
- Gonads are the primary source of androgens in Mozambique tilapia.
- Androgens are essential for the expression of reproductive behaviors.
- Aggressive behavior appears independent of gonadal androgens, regulated by separate central mechanisms.
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