Embryonic use of energy and post-hatching yolk in the gray rat snake, Ptyas korros (Colubridae)

Female Ptyas korros from a population on Dinghai, Zhoushan Islands, in east ern China, produced one clutch per breeding season. Clutch size varied from 7 to 14, and was positively correlated with female SVL. The duration of in cubation at 30 +/- 0.5 degrees C averaged 54.7 days. Dried shells from fres hly laid eggs averaged 30.0% of the entire egg dry mass. Egg contents of th e freshly laid egg contained higher quantities of dry material, non-polar l ipids and energy than did newly hatched hatchlings. Shells from freshly lai d eggs contained higher quantities of ash than did those from hatched eggs. During incubation, approximately 77% of dry material, 54% of non-polar lip ids and 69% of energy in the egg contents of freshly laid eggs were transfe rred to the hatchling. There were inverse relationships between carcass dry mass, post-hatching yolk dry mass and fat body dry mass for hatchlings sam pled immediately after hatching. Posthatching yolk could be used to support subsequent growth of newly emerged young, as indicated by significant incr eases in the carcass dry mass and SVL of hatchlings during their first days of life, following the depletion of post-hatching yolk.