CONICET | Buscador de Institutos y Recursos Humanos

In crocodilians, the rate of embryonic development and consequently the duration of the incubation period are affected by temperature. Since incubation temperature has strong influences on embryo development by altering metabolism rate, we manipulated oxygen concentration in order to uncouple the effects of developmental rate from the direct effects of temperature. Here we consider whether oxygen concentration has influence on differentiation rate (or progression from one stage to the next) and growth (body mass and total length). Thus, we incubated Caiman latirostris eggs at two different temperatures (31ºC, 100% female-producing temperature, and 33ºC, 100% male-producing temperature) and at two O2 concentrations (15% and 21%). We monitored the developmental stages of embryos within the thermosensitive period (Stage 20-24). Incubation under hypoxia reduced embryonic growth, but it had no effect on differentiation rate. Our results suggest that both, temperature and oxygen concentration, affect yolk-to-tissue conversion rate (and thus embryo size), and differentiation rate is affected only by incubation temperature.