CONICET | Buscador de Institutos y Recursos Humanos

The gonadal outcome in some reptiles is regulated by temperature during a critical period of the embryonic development; and steroidal hormones are seen as effectors of the gonadal differentiation process. Recently, cortisol has also been implicated in the temperature-dependent sex determination (TSD) process of fish. Corticosterone, the glucocorticoid stress-related hormone in reptiles, has been considered as a potential modulator of the gonadal differentiation process. In fact in some reptiles a feminizing effect of corticosterone was described. This hormone plays a significant role in the intermediate metabolism, osmoregulation, growth, and reproduction; and its plasmatic levels rise under stressful situations. In this context, we aim at assessing whether stress-related hormones can affect the sex differentiation process of Caiman latirostris, a species with strong TSD, using a glucocorticoid agonist, dexamethasone. As a first step, we incubated embryos at masculinizing temperatures (33°C; 100% males). Different doses of dexamethasone were topically applied to the eggshell at stage 22, previously to the first morphological signs of gonadal differentiation. Embryonic mortality was not affected by dexamethasone manipulation. No effects of dexamethasone on sex differentiation were found, and all histologically analyzed individuals evidenced testis. However, hatchlings from dexamethasone treated eggs had a shorter incubation time and were also heavier and larger than control ones. Our results do not account for a dexamethasone involvement in ovarian differentiation, at least at temperature that produces 100% males. Nevertheless, they suggest that dexamethasone might improve embryo development by enhancing intermediate metabolism, or by direct stimulation of growth hormone secretion.

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