Water Relations of Embryonic Snapping Turtles (Chelydra serpentina) Exposed to Wet or Dry Environments at Different Times in Incubation

Flexible-shelled eggs of common snapping turtles (Chelydra serpentina) were halfburied in wet (water potential = -150 kPa) or dry vermiculite (water potential = -950 kPa), and then were incubated in covered containers at 29.0 C. Half the eggs on each substrate were transferred to the other substrate at the end of the first trimester of development, and half the eggs were transferred between wet and dry substrates at the end of the second trimester. Thus, the experiment conformed with a 2₃ factorial design in which eight treatment groups were recognized on the basis of the hydric conditions encountered by eggs during each of the three trimesters of incubation (wetwet-wet, wet-wet-dry, etc.). Hydric conditions encountered at any time during incubation affected the pattern of net water exchange between eggs and their surroundings and also influenced the size of hatchlings and the amount of residual yolk available to sustain emergent young. Size of hatchlings was positively correlated with net water exchange by eggs, but mass of the residual yolk was negatively correlated with net water exchange. Thus, water exchanges occurring at any time in incubation seemingly influence the size of the pool of water available inside eggs, and the size of this pool of water, in turn, affects physiological processes that influence body size and nutrient reserves in hatchlings.