MULLINS, M.A.*; JANZEN, F.J.: Thermal Ecology of Smooth Softshell Turtle (Apalone mutica) Embryos

Smooth softshell turtles (Apalone mutica) bear eggs with hard, water-resistant shells which presumably insulate them from all environmental factors except temperature. To evaluate the phenotypic effects of different mean temperatures and different thermal variances, and to separate temperature effects from maternal effects, eggs from 10 clutches were equally distributed among six temperature treatments: three each at a mean of 28.5 or 32.5°C, with ranges of +/- 0, 2, or 4°C. Hatchlings from these clutches were measured and evaluated based on righting time and swimming performance. Clutch had a significant effect on all traits examined except for righting time. Consistent with much previous research, the cooler 28.5°C mean temperature treatments produced larger hatchlings for all size measurements and took longer to hatch. Contrary to expectations, temperature had no effect on swimming performance or righting response. To evaluate the ecological importance of observed differences in terms of short-term survival, a controlled release of these hatchlings into a field enclosure was undertaken. The results of this release will also be discussed.