The effects of thermal and hydric environments on hatching success, embryonic use of energy and hatchling traits in a colubrid snake, Elaphe carinata

Abstract

We examined the effects of thermal and hydric environments on hatching success, the embryonic use of energy and hatchling traits in a colubrid snake, Elaphe carinata. The eggs were incubated at four temperatures ranging from 24 to 32°C on substrates with water potentials of 0 and −220 kPa using a 4×2 factorial design. Both thermal and hydric environments affected the water exchange between eggs and their surroundings. Eggs incubated in wetter substrates gained mass throughout the course of incubation, whereas eggs in drier substrates gained mass during the first half of incubation and lost mass thereafter. Hatching success was noticeably higher at 26 and 30°C than at 24 and 32°C, but among treatments, differences in hatching success were not significant. Temperature significantly affected the duration of incubation and most hatchling traits examined. Deformed hatchlings were found in all temperature treatments, with more deformities observed at 32°C. Hatchlings from eggs incubated at different temperatures differed in wet body mass, but the differences stemmed mainly from variation in water contents. Embryos at different temperatures completed development at nearly the same expenditure of energy and catabolized nearly the same amount of lipids, but hatchlings from different temperatures differed in the development condition of carcass at hatching. Hatchlings from eggs incubated at 26°C were larger in SVL than those from other higher or lower incubation temperatures, characteristically having larger carcasses; hatchlings from 32°C eggs were smaller in SVL and had smaller carcasses but larger residual yolks than those from lower incubation temperatures. Hatchlings from eggs incubated at 24°C were shorter in tail length but greater in size (SVL)-specific body wet mass than those from higher incubation temperatures. Within the range from −220 to 0 kPa, the substrate water potential did not affect hatching success, the embryonic use of energy and all hatchling traits examined, and the effects of temperature were independent of the effects of substrate water potential. Therefore, our data add evidence showing that embryonic development in reptiles with pliable-shelled eggs is relatively insensitive to variation in hydric environments during incubation.