Water relations of pliable-shelled eggs of common snapping turtles (Chelydra serpentina)

Abstract

Pliable-shelled eggs of common snapping turtles were incubated at 29 °C under hydric conditions simulating those to which eggs are exposed in natural nests. Eggs exposed to conditions similar to those encountered at the centre of nests experienced net declines in mass during incubation, presumably owing to the loss of water vapour to air trapped inside the chamber. Eggs exposed to conditions similar to those encountered at the periphery of nests absorbed liquid water across that part of their shell contacting the substrate and increased in mass during the early weeks of incubation. However, transpirational water loss from exposed surfaces of these eggs seemed to increase coincident with metabolism of developing embryos, and became high enough by the midpoint of incubation that absorption of liquid water could not compensate for the loss of water vapour, thereby causing eggs to decline in mass for the remainder of incubation. The size of hatchlings was related both to the position of eggs inside the chamber and to wetness of the substrate, indicating that the water exchanges of pliable-shelled eggs of snapping turtles may be of considerable importance to developing embryos.