An experimental analysis of the water relations of eggs of Blanding's turtles (Emydoidea blandingii)

Abstract

Eggs of Blanding's turtles (Emydoidea blandingii) were incubated in the laboratory under hydric conditions eliciting different patterns of net water exchange between eggs and surrounding air and substrate. Eggs incubated on wet and intermediate substrates increased in mass during the first half of incubation and decreased in mass during the second half, and their mass just before hatching was slightly lower than at oviposition. Eggs incubated on dry substrates and on platforms above substrates declined in mass throughout incubation, with a rate of decline greater in the second half of incubation than in the first. The size of hatchlings was related to the hydric environment in which eggs were incubated and, possibly, to the net flux of water across eggshells. However, variation in size of hatchlings was not as great as has been reported for other species with flexible-shelled eggs, owing presumably to the constraints on water exchange imposed by the more complex eggshells of Blanding's turtles.