Synthesis of sex steroids and expression of sex steroid receptors during gonadal development of the snail-eating turtle Malayemys macrocephala (Gray, 1859)

Prior studies on the freshwater turtle Malayemys macrocephala showed that the incubation temperature influenced somatic and gonadal development, supporting temperature-dependent sex determination. This study aimed to examine the onset of steroidogenesis and expression of steroid receptors during gonadal development of M. macrocephala. Embryos at the sexually undifferentiated gonad (stages 14–16), differentiating gonad (stages 17–22), and differentiated gonad (stages 23–25) stages reared at the male- and female-producing temperatures (26 °C and 32 °C, respectively) were examined. Gonads were assessed for steroidogenic potential by immunofluorescence staining using antibodies against 3β-hydroxysteroid dehydrogenase (3β-HSD), 17β-hydroxysteroid dehydrogenase (17β-HSD), and P450 aromatase (P450arom), as well as the androgen receptor (AR) and estrogen receptor α (ERα). In males, expression of these steroidogenic enzymes and steroid receptors were found as follows: 3β-HSD at stages 14–22, 17β-HSD at stages 14–25, and AR at stages 17–25. In females, the expression was as follows: 3β-HSD and 17β-HSD at stages 14–22, P450arom at stages 19–25, and ERα at stages 19–25. Overall, the results suggest that in gonadal development of M. macrocephala: 3β-HSD plays a role as a key enzyme in the biosynthesis of sex steroids, 17β-HSD and the AR play roles in testis development, and P450arom and the ERα are involved in ovary development.