Comparative Morphology of the Penis and Clitoris in Four Species of Moles (Talpidae)

Abstract

The penile and clitorial anatomy of four species of Talpid moles (broad-footed, star-nosed, hairy-tailed, and Japanese shrew moles) were investigated to define penile and clitoral anatomy and to examine the relationship of the clitoral anatomy with the presence or absence of ovotestes. The ovotestis contains ovarian tissue and glandular tissue resembling fetal testicular tissue and can produce androgens. The ovotestis is present in star-nosed and hairy-tailed moles, but not in broad-footed and Japanese shrew moles. Using histology, 3D reconstruction, and morphometric analysis, sexual dimorphism was examined in regard to a nine feature masculine trait score that included perineal appendage length (prepuce), anogenital distance, and presence/absence of bone. The presence/absence of ovotestes was discordant in all four mole species for sex differentiation features. For many sex differentiation features, discordance with ovotestes was observed in at least one mole species. The degree of concordance with ovotestes was highest for hairy-tailed moles and lowest for broad-footed moles. In relationship to phylogenetic clade, sex differentiation features also did not correlate with the similarity/divergence of the features and presence/absence of ovotestes. Hairy-tailed and Japanese shrew moles reside in separated clades, but they exhibit a high degree of congruence. Broad-footed and hairy-tailed moles reside within the same clade but had one of the lowest correlations in features and presence/absence of ovotestes. Thus, phylogenetic affinity and the presence/absence of ovotestes are poor predictors for most sex differentiation features within mole external genitalia.

Spotted hyaenas and the sexual spectrum: reproductive endocrinology and development

“…Moreover, she is certainly not alone in possessing a hypertrophied clitoris (e.g. proboscideans, elephant (Glickman et al 2005); primates including platyrrhines (Campbell 2017, Carosi et al 2020, strepsirrhines and others (Hill 1953, Dixson 1998, Drea & Weil 2008; viverrids (Hawkins et al 2002); talpids (Sinclair et al 2017)), suggesting that successful birth via this structure is what, ironically, derails notions about her femininity. These incongruities illustrate the inadequacy of a male-centric definition of reproductive biology.…”

Development of the human penis and clitoris

“…In the spotted hyena male and female phalluses are approximately the same size in adulthood (Cunha et al, 2014), and penile and clitoral growth (length) has been shown to be androgen-independent in spotted hyenas (Glickman et al, 1992; Glickman et al, 1998). The prepuce of several species of moles is of similar size in both males and females (Sinclair et al, 2016b). In these examples various aspect of male external genitalia are only slightly larger than their female counterparts, raising the possibility that certain aspects of development/growth of male external genitalia are androgen-independent.…”

Androgen-independent events in penile development in humans and animals

“…The internally positioned clitoris of broad-footed moles is defined by a U-shaped clitoral epithelial lamina similar to that of the mouse clitoris (Cunha et al, 2019a;Martin-Alguacil et al, 2008b;Sinclair et al, 2016c). These findings of mole external genitalia were confirmed in a subsequent paper on the comparative anatomy of 4 species of moles (Sinclair et al, 2016b). As in mice, adult size of the perineal appendage is slightly greater in male than female moles.…”