Does Corticosterone Exposure during Embryonic Development Affects Sex Ratios in Caiman latirostris, a Reptile with Temperature-Dependent Sex Determination (TSD)?

JOSEFINA LUCIANA IUNGMAN; MARIA VIRGINIA PARACHÚ MARCÓ; EVANGELINA VIOTTO ; GUSTAVO SOMOZA; CARLOS IGNACIO PIÑA

Santa Fe

Congreso; 25th Working Meeting of the IUCN-SSC Crocodile Specialist Group; 2018

Universidad Nacional del Litoral - Proyecto Yacare

It is known, that the sex of broad-snouted caiman embryos is regulated by temperature during a critical period of the embryonic development; and the interplay between temperature and steroid hormones can direct the phenotypical embryos´ sex. Recently, stress and glucocorticoids (GCs) -stress-related hormones- have considered as potential modulators of the gonadal differentiation process. For example, cortisol manipulation result in sex inversion in fish larvae; and high corticosterone levels bias offspring sex ratio towards males in some lizards. In this context, we aim to assess whether corticosterone (the main GC produced in reptiles) can mediate between temperature and sex differentiation of Caiman latirostris. As a first step, we incubated embryos at 32 ± 0.2 °C (a transitional range in temperature that would produce 70% females). Different doses of corticosterone (1.4 ppm and 0.014 ppm) were topically applied to the eggshell at stage 20, prior gonadal differentiation. None of treatments had affected embryos survival. The expected sex outcome was skewed to males by high corticosterone dose. In addition, hatchlings from corticosterone treated eggs, at low dose, were the earliest to hatch and were also the longest and heaviest. Our results suggest a role of corticosterone in the masculinization process of broad-snouted caiman. They also provide a possible link between stress experienced by a reproducing female and a trade-off involving enhanced growth or male biased sex ratio, and hence the fitness of her offspring.