Optimal temperatures for egg incubation in two Geoemydid turtles: Ocadia sinensis and Mauremys mutica

Egg incubation is critical for artificial reproduction of turtles, but how incubation conditions affect embryos and resultant hatchlings remains unknown in many species. We investigated the influence of temperatures on incubation period, hatching success and hatchling traits to indentify the optimal temperatures for egg incubation in two Geoemydid turtles (Ocadia sinensis and Mauremys mutica). Incubation period of O. sinensis eggs was shorter than that of M. mutica eggs. In both species, hatching success was high in the temperature range of 26-30 degrees C, and hatchlings were mainly males if incubated at low temperatures and females at high temperatures. The pivotal temperature for sex determination fell into the range of 28-30 degrees C for O. sinensis and 26-28 degrees C for M. mutica. Incubation temperature profoundly affected post-hatching growth in M. mutica, but not in O. sinensis. Hatchling M. mutica from 24 and 26 degrees C grew faster than those from 28 and 30 degrees C. Therefore, temperatures around 26 or 28 degrees C would be optimal incubation temperatures for M. mutica or O. sinensis to improve hatching success and post-hatching growth, and to yield offspring with a balanced sex ratio. Moreover, this study demonstrates significant inter- and intra-specific variations in optimal incubation temperature and pivotal temperature, which implies that simply adopting incubation regimes developed for other species or populations should be avoided in turtle aquaculture. (C) 2010 Elsevier B.V. All rights reserved.