Female gonad of moles, genus Talpa (Insectivora, Mammalia): Ovary or ovotestis?

The female gonads of moles (genus Talpa) are composed of a cortex, function ing as an ovary, and a medulla, which is structurally similar to that of th e testis. In the female reproductive apparatus there are masculine glandula r annexes, such as a bilobate prostate, two Cowper glands, and a penis-like clitoris. All these features have recently led to the hypothesis of the pr esence of hermaphroditism due to sex-reversal in Talpa. The purpose of this study is to understand the functional significance of the structural organ ization of the female gonads in order to verify this hypothesis. Histologic al, histochemical and ultrastructural analyses have been carried out on sev eral gonads of both sexes of two species: T. europaea and T. romana, includ ing three fetuses. In both species, the cortical region of the female gonad shows a regular oogenetic activity. While the medulla is composed of inter stitial cells that are partly organized in cord-like structures, no spermat ogenetic activity has been ever observed inside of them. A histochemical an alysis shows that in both sexes the interstitial cells secrete steroids, pr esumably estrogens as well as androgens. The presence of androgens in the f emale gonads would therefore explain the persistence of male glandular anne xes in the female reproductive apparatus and both the sexual and behavioral monomorphism typical of the genus Talpa. Nonetheless, the female gonad of moles is a real ovary and a well-defined gonochorism exists. Therefore, the re is no reason to assert the presence of hermaphroditism due to sex revers al. J. Exp. Zool. 286:745-754, 2000. (C) 2000 Wiley-Liss, Inc.