Possible adaptive value of water exchanges in flexible-shelled eggs of turtles.

Use of energy reserves by embryos of common snapping turtles (Chelydra serpentina) is related to the hydric conditions to which eggs are exposed during incubation and to the net exchanges of water through the eggshells. Embryos developing inside eggs with a relatively favorable water balance use more of their energy reserves metabolically and grow larger before hatching than embryos inside eggs with less favorable water exchanges.