Gonadal development in scorpion mud-turtles, Kinosternon scorpioides, in a controlled environment

Research on gonadal development including sexual differentiation of gonads in chelonians is essential for understanding the mechanisms that determine offspring sex and, consequently, the sex ratio of egg clutches. This directly impacts population structure, as sex ratios influence reproductive dynamics and species' long-term viability. The aim of this study was to characterize the gonadal development of scorpion mud-turtle (Kinosternon scorpioides). A total of 85 embryos from stages 12-26 were analyzed, kept under digital temperature control (28.5 ± 0.5°C). The reproductive system was dissected and processed for histological analysis using light and transmission electron microscopy. The average incubation time was 117.35 ± 9.5 days. From stage 12 onwards, gonadal ridges containing primordial germ cells (PGCs) were observed. At stage 14, the undifferentiated gonads consisted of cuboidal coelomic epithelial cells that invaginated to form cord-like structures containing germ cells. At stage 20, at approximately 50 days of incubation, sexual differentiation of gonads was noted. The ovaries showed a cortical region containing oogonia and oocytes, and a medullary region with a stroma rich in vessels. The testes were characterized by a peripheral band of dense connective tissue beneath the tunica albuginea, and by the presence of seminiferous tubules occupying the central portion of the organ. The results of this study provide important information on the gonadal development of K. scorpioides, as the identification of the moment of gonadal differentiation, stage 20, makes it possible to understand the influence of the environment on sex determination. These findings provide support for the reproductive management of K. scorpioides and can be applied directly to the sexual control of populations in situ and ex situ.