FURTHER STUDIES ON EGG INCUBATION OF AN OVIPAROUS SNAKE, DINODON RUFOZONATUM(COLUBRIDAE), WITH COMMENTS ON THE INFLUENCE OF HYDRIC ENVIRONMETS

We incubated eggs of red-banded wolf snakes (Dinodon rufozonatum) at 24 and 30℃ on substrates with water potentials of 0 and -500 kPa using a 2×2 factorial design, paying particular attention to the influence of substrate moisture and its interaction with incubation temperature on hatching success, embryonic use of energy and material and hatchling traits. All viable eggs gained mass during incubation due to absorption of water, and both thermal and hydric environments affected water exchanges between eggs and their surroundings, thereby affecting the hydric conditions inside the egg. Eggs incubated at 24℃ gained more mass than did eggs at 30℃ but at the same substrate water potential; eggs incubated in wetter substrates (0 kPa) gained more mass than did eggs in drier substrates (-500 kPa) but at the same temperature. Incubation temperature significantly affected duration of incubation, but substrate moisture and its interaction with temperature did not. In our study, both incubation temperature and substrate moisture did not affect hatching success and sex ratio of hatchlings. Deformed hatchlings were found in each treatment, the frequency being independent of treatments. Substrate moisture significantly affected size (SVL), wet mass and carcass dry mass of hatchlings, with those incubated in wetter substrates being larger in SVL, wet body mass and carcass dry mass than those in drier substrates. Variation in hatchling wet body mass among treatments stemmed mainly from variation in water contents, because there were no significant differences in total dry mass among hatchlings from different incubation conditions designed in this study. More yolk remained unutilized at hatching when eggs were incubated at 30℃. Hatchlings incubated at 30℃ contained more ash than did those incubated at 24℃, largely because they contained more ash in the residual yolk. Hatchlings incubated at 24℃ contained more energy than did those incubated at 30℃, suggesting greater energy expenditure for embryonic development at 30℃ than at 24℃. Of all hatchling traits examined, only residual yolk dry mass was affected by interaction between temperature and moisture. In all treatment locomotor performance (the maximum distance of continuous locomotion) was not correlated with hatchling SVL. A two-way ANOVA indicated that there were no significant effects of incubation temperature, of substrate moisture and of their interaction on locomotor performance of hatchlings. Taken together, our results reveal that the effects of substrate moisture on incubation of D. rufozonatum egg are of minor importance, and therefore support the conclusion that variation in hydric environments over a wide range does not have important effects on incubation of pliable-shelled reptilian eggs.