Does the hydric environment affect the incubation of small rigid-shelled turtle eggs?

Hydric environments are hypothesized to have minor effects on the embryonic development of rigid-shelled turtle eggs due to the low water permeability of the eggshell. However, the water reserve in the eggs may still influence their resistance to environmentally induced dehydration. We incubated rigid-shelled turtle eggs (Pelodiscus sinensis) on different moist substrates (from -12 to -750kPa) to test the hypothesis that small rigid-shelled eggs would be sensitive to hydric environments. The hydric treatment significantly affected the incubation period, with eggs incubated in the moistest and driest substrates taking longer to hatch than those on the medium-moisture substrates. Hatching success was slightly lower for eggs incubated in dry conditions than those in wet conditions, but the difference was not statistically significant. The heart rates of early embryos were lower on moist substrates than those on dry substrates, but this difference disappeared in late embryos. Hatchlings from the moistest substrate were larger (in carapace length and width) and heavier than those from drier substrates. However, the dry body mass of the hatchlings did not differ among the hydric treatments. The functional performance (righting response) of the hatchlings was affected by the hydric environment. The time to right was shorter for the hatchlings from the substrate of -12kPa than those from -220kPa. These results are consistent with the hypothesis that the hydric environment may significantly affect developing embryos and the resulting hatchlings in turtle species, such as P. sinensis, with small rigid-shelled eggs.