Intersexual dominance, masculinized genitals and prenatal steroids: comparative data from lemurid primates
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Masculinization of female genitalia and female intersexual dominance distinguish spotted hyenas (Crocuta crocuta) and Malagasy primates (Lemuriformes) from most other mammals. An unusual prenatal endocrine environment has been proposed to proximately underlie the development of these traits in hyenas. To examine whether female dominance and genital masculinization are similarly enhanced by the prenatal environment in lemurid primates, we measured androgen and estrogen excretion in pregnant wild redfronted lemurs (Eulemur fulvus rufus). Our results showed that estrogen levels during the second phase of gestation were much higher in females carrying a male fetus than in female-carrying mothers. This may indicate the onset of testicular activity in male fetuses, because androgens of fetal origin are aromatized to maternal estrogens. Levels of androgen excretion were similar in all mothers regardless of the fetus' sex, which may suggest that androgen-independent mechanisms also contribute to female masculinization. The much higher androgen/estrogen ratio in female-carrying mothers indicates that relative, rather than absolute, prenatal steroid concentrations may play a role in female masculinization.
KeywordsAndrogen Male Fetus Female Dominance Prenatal Androgen Spotted Hyena
We thank M. Razafindrasamba and N. Rabarjiaona for their help with fecal sample collection and A. Heistermann for help in the laboratory. The manuscript was substantially improved with the help of comments made by Oliver Schülke and three anonymous referees. Financial support was provided by the DFG (Ka 1082/4-1, 4-2). This study complies with the current laws of the countries in which it was conducted.
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