Abstract

Many oviparous species rely on hatching cues to ensure hatchlings maximize their survival, given the external environmental conditions. In nature, these cues are traditionally environmental (e.g., temperature) or social (e.g., communication between embryos). Examples of both are common throughout ectothermic taxa, particularly reptiles. In the present study, we explored the role of temperature in hatch timing in Snapping Turtles (Chelydra serpentina). We allowed embryos to incubate in wild nests for the majority of embryonic development, then isolated embryos in the lab, and maintained them at 24°C until they reached Yntema stage 25. At this developmental stage, external morphological differentiation is complete and yolk resorption begins. We then incubated embryos until pipping across a range of constant but biologically relevant temperatures (20, 23, 25, 28, or 30.5°C). To test whether thermal variance acts as a hatching cue, we also included a treatment in which temperature fluctuated diurnally around a stationary mean (25 ± 4°C). We found that the timing of egg pipping was not related to temperature treatment, thermal fluctuation, or sex of the embryo. Thus, contrary to traditional understanding, temperatures in the range studied do not affect the duration of the final embryonic stage in C. serpentina embryos, and a definitive hatching cue in this species is yet unknown.