AN EXTENDED INCUBATION PERIOD IS NOT ENOUGH TO DETERMINE HATCHLINGS SEX

IUNGMAN, J.; PIÑA, C.I.

Manaos

Congreso; 20th Working Meeting of the Crocodile Specialista Group (CSG/SSC/IUCN); 2010

CSG/SSC/UICN

The influence of temperature on the outcome of sexual differentiation in crocodilians is well established. At present, there is no evidence of a putative target for temperature. Some authors have postulated that both, developmental rate during its first third and incubation period are better predictors of sex than incubation temperature. In Caiman latirostris, incubation at 33 ºC simultaneously induces shorter incubation time, and males. If the rate of development (defined in its narrowest sense as morphological changes) is more reliable than temperature to predict the sex, any factor capable of modifying the developmental rate-temperature relationship has the potential to control hatchling sex. Here, we consider whether hypoxia influences gonadal sex by affecting either the developmental rate or the incubation period, or both. Thus, caiman eggs were incubated at 31 °C and 33 °C (yielding 100 % females and 100 % males, respectively) and under various oxygen concentrations. Oxygen levels modified incubation period, but they did not affect sex determination. Nevertheless, by assessing embryos during their thermosensitive period (Stage 20-24), we observed that developmental stages were the same between oxygen treatments, despite of their differences in the timing of hatching. Our data do not support the hypothesis that sex ratio in C. latirostris is mediated by incubation time or oxygen availability during embryogenesis, at less under our incubation treatments