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Advisor(s)
Abstract(s)
The effects of castration and sex steroid manipulations on the expression of sexual behavior were investigated in a small fish, the peacock
blenny, Salaria pavo. In this species, large males defend nests and attract females while small “sneaker” males reproduce by imitating the female
morphology and courtship behavior in order to approach nests during spawning events and parasitically fertilize eggs. Sneakers switch into nest
holders in their second breeding season, thus displaying both male and female-like sexual behavior during their lifetime. We tested the effects of
castration and of an aromatase inhibitor (Fadrozole, F), testosterone (T) or 17β-estradiol (E2) implants on the expression of male and female-like
behavior in sneakers. Sneakers were either sham-operated, castrated or castrated and implanted with vehicle, F, T+F or E2+F. Seven days after the
treatment, sneakers were placed in a tank with a nesting male, two ripe females and an available nest. Castrated fish had lower levels of circulating
T and increased the time spent displaying female typical nuptial coloration. T implants had the opposite effect, inhibiting the expression of femalelike
behavior and coloration. E2 implants had no significant effect on the display of sexual behavior but the frequency of aggressive displays
decreased. The results agree with previous findings in sneakers of S. pavo that demonstrated an inhibition of female-like behavior by 11-
ketotestosterone (11-KT). The reported increase in T and 11-KT production when sneakers change into nest holders may thus contribute to
behaviorally defeminize sneakers. Contrarily, both T and E2 failed to promote male-like behavior, suggesting that behavioral masculization during
tactic switching depends on other neuroendocrine mechanisms or that the time length of the experiment was insufficient to induce male-like
behavioral changes in sneakers.
Description
Keywords
Aromatase Sex steroids Reproductive behavior Salaria pavo Peacock blenny Androgens Estrogens Implants Alternative reproductive tactics Fadrozole
Citation
Hormones and Behavior, 51, 534-541