Water exchange of flexible-shelled eggs and its effect on hatchling traits in the Chinese skink, Eumeces chinensis

Abstract

Flexible-shelled eggs of the Chinese skink (Eumeces chinensis) were used to determine the routes of water exchange with the environment and the effects of water exchange on hatchling traits. Eggs were incubated under three different hydric conditions at 28 degrees C. One group (ground eggs) was half-buried in incubation substrate. The second group (upper eggs) rested on the ground eggs but did not contact the substrate directly, and the third group was placed on a plastic platform above the substrate. Ground and upper eggs increased in mass and hatched successfully, while all eggs resting on the plastic platform lost mass and died within a week. Hence, E. chinensis eggs cannot sustain water balance through exchange of water vapor in air alone, but can absorb water from the substrate and other eggs and develop well. Water gained by upper eggs was only 20% of that absorbed by ground eggs, but hatchlings from the two treatments did not differ in morphology or locomotor performance. Therefore, the degree of water exchange of E. chinesis eggs has little effect on embryonic development and hatchling traits. The insensitivity of the eggs to variations in water exchange may be an adaptation against extreme hydric conditions in a species that deposits its eggs close to the soil surface.