Effects of Hydric Conditions During the Incubation of Common Snapping Turtle (Chelydra serpentina serpentina) Eggs on Hatchling Evaporative Water Loss and Microhabitat Selection During a Simulated Nest Exodus
Knickerbocker, Debra Lynn
Abiotic factors during incubation can influence embryonic development in ways which may have serious consequences for the resulting hatchlings. It has been shown in aquatic turtles that incubation on a substrate with a positive osmotic gradient (favoring water movement from the soil into the egg) causes hatchlings that are larger than those incubated on a substrate with a negative gradient (favoring water movement from the egg to the soil). To discover possible survival differences accompanying this difference in size, I incubated 16 clutches of Chelydra serpentina eggs in vermiculite with two different water potentials (-150 kPa for the wet ("positive") and -850 kPa for the dry ("negative")). Resultant hatchlings were released in an enclosure containing 3 different degrees of vegetational cover to simulate a nest exodus. Wet hatchlings were significantly larger than the dry hatchlings. Under field conditions, wet-incubated hatchlings had a significantly higher evaporative water loss than did the dry-incubated hatchlings. The percentage of total distance traveled was higher for dryincubated hatchlings in high vegetational cover than for wet-incubated hatchlings and significantly higher in low vegetational cover for the wetincubated hatchlings than for the dry-incubated hatchlings. These results suggest that dry-incubated hatchlings can avoid dehydration (to which they are more susceptible) by selecting habitats for migration which retard evaporative water loss. Considering most size differences in hatchling turtles in natural nests are caused more often by initial egg size, it seems unlikely that hydric conditions in the nest have a significant effect on the survival of hatchling turtles under field conditions.
vi, 53 p.
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