Steroidogenesis during Dry and Wet Season of Free-Living Male Scorpion Mud Turtle (Kinosternon scorpioides)

This study aimed to elucidate seasonal reproductive patterns by associating the immunolocalization of the steroidogenic enzymes responsible for estrogen and androgen synthesis, cytochromes P450 aromatases (P450 arom), 17-hydroxylase/17,20-lyase (P450c17) respectively, as well as the redox partner NADPH cytochrome P450 oxido-reductase (CPR) in the male mud turtle (Kinosternon scorpioides). The animals were collected at São Bento, Maranhão, Brazil. Testicles and epidydimes from 38 adult animals were characterized by immunohistochemistry (IHC) and western blotting. Data were analyzed in two seasons: dry and wet season. In addition, the gonadosomatic index, morphometry, concentrations of testosterone, corticosterone, and estradiol were analyzed. The changes in biometrics, cell morphometry, and testicular steroidogenesis between the wet and dry seasons support that estrogen produced by the Leydig cells might influence germ cell production during spermatogenesis, and the expression of the enzymes P450 arom and P450c17 in the Leydig cells that play a role in testicular quiescence. We found that the P450arom, P450c17, and CPR are present in the testes and epididymides at both seasons. These findings support a state of male reproductive quiescence during the dry season and active spermatogenesis in the wet season.