Growth period of Kinosternon scorpioides changes the ovary morphology by follicular differentiation and structural reorganization.

Knowledge of gonadal morphophysiology is essential for implementing techniques that can improve reproduction, production, and conservation. This study described the ovarian morphology and oocyte maturation of Kinosternon scorpioides during three growth stages: hatchlings, juveniles, and adults. Ovaries from 20 females were analyzed across these stages. The ovarian follicles were classified into four stages: hatchlings, juveniles and adults. The ovarian follicles were classified into four stages: stage I, characterized by the presence of the granulosa layer; stage II, which showed vesicles in the cytoplasm, in addition to the zona pellucida; stage III, where yolk platelets were observed at the periphery of the oocyte; and stage IV, in which the quantity of yolk platelets increased. In hatchlings, small follicles, covered by a flattened layer of follicular cells (stage I), as well as oogonia, were observed. In juveniles, pre-vitellogenic follicles (stages I and II) were identified, suggesting the onset of puberty, alongside the presence of oogonia. In adult females, larger follicles (stages III and IV) were found, containing yolk, oogonia, corpus luteum, and evidence of follicular atresia. This study revealed distinct morphological and functional changes from hatchlings to adults, with follicular maturation involving significant alterations in structures related to nutrition, protection, and steroidogenesis. These findings provide valuable insights into reproductive mechanisms, supporting improved management strategies and conservation efforts for this species.