Temperature- vs. estrogen-induced sex determination in Caiman latirostris embryos: Both females, but with different expression patterns of key molecules involved in ovarian development

Caiman latirostris is a species with temperature dependent sex determination (TSD), which implies that the incubation temperature of the eggs is the main factor that determines the sex during a thermo-sensitive period (TSP). However, estrogens play a critical role in this process. The administration of 17β-estradiol (E2) previous to TSP overrides the effects of male incubation temperature, producing phenotypic females. This effect has been defined as sex reversal or estrogen-induced sex determination (E2SD). The aim of the present study is to describe similarities and differences in the effects of TSD and E2SD treatment conditions on ovary development. Our results show that the two treatment conditions studied are able to produce different ovaries. Treatment with E2 modified the expression pattern of estrogen receptor alpha and progesterone receptor, and expression of the enzyme aromatase. Moreover, in E2SD females, the proliferation/apoptosis dynamic was also altered and high expression of TAp63 was observed suggesting the presence of greater DNA damage in germ cells. To the best of our knowledge, this is the first report that describes the morphology of the female gonad of C. latirostris in three stages of embryonic development and shows the expression of TAp63 during the gonad development of a reptile. It is important to emphasize that the changes demonstrated in E2SD female gonads of embryos show that environmental compounds with proven estrogenic activity alter the follicular dynamics of C. latirostris in neonatal as much as in juvenile animals, endangering their reproductive health and possibly bringing consequences to ecology and evolution.