Meeting Abstract
Diurnal fluctuations in nest temperature have been shown to affect incubation duration as well as the sex, physiological performance, and size of hatchling turtles. The influence of temperature fluctuation on embryonic growth and development rates at different developmental phases, however, is not well understood. In this experiment, I incubated Snapping Turtle (Chelydra serpentina) eggs at either “constant” (25 ± 0.5 °C) or “fluctuating” (12 h at 29 ± 0.5 °C, 12 h at 21 ± 0.5 °C) thermal conditions. I sampled embryos at predicted time intervals for the onset of organogenesis (Yntema stage 10), the onset of early growth (YS 14), and the onset of late growth (YS 19) as well as at hatching. Embryo dry mass and development stage did not differ between the two groups early in the organogenesis phase, but by the onset early growth phase embryos in the fluctuating thermal treatment had significantly higher dry masses (~42% greater) and were more developed (by ~1 Yntema stage) than those in the constant thermal treatment. The proportional size and developmental difference observed at the beginning of the early growth phase persisted into the beginning of the late growth phase. However, there was no significant difference in incubation duration, in hatchling dry mass, or in various linear measurements of hatchling size between the two treatments. These findings suggest that the organogenesis phase of development is particularly sensitive to diurnal fluctuations in temperature with respect to both growth and development. Overall growth during the late growth stage of embryogenesis, however, appears to be largely determined by the overall size of the egg and the resources contained within, resulting in little difference in hatchling size as a result of fluctuating incubation temperature.
