Data from: Turtle embryos move to optimal thermal environments within the egg

A recent study demonstrated that the embryos of soft-shelled turtles can reposition themselves within their eggs to exploit locally warm conditions. In the current paper, we ask whether turtle embryos actively seek out optimal thermal environments for their development, as do post-hatching individuals. Specifically, (1) do reptile embryos move away from dangerously-high temperatures, as well as towards warm temperatures? and (2) is such embryonic movement due to active thermoregulation, or (more simply) to passive embryonic repositioning caused by local heat-induced changes in viscosity of fluids within the egg? Our experiments with an emydid turtle (Chinemys reevesii) show that embryos avoid dangerously high temperatures by moving to cooler regions of the egg. The repositioning of embryos is an active not passive process: live embryos move toward a heat source, whereas dead ones do not. Overall, our results suggest that behavioural thermoregulation by turtle embryos is an active process, genuinely analogous to the thermoregulatory behaviour exhibited by post-hatching ectotherms.

近期一项研究证实，软壳龟（soft-shelled turtle）的胚胎可在卵内调整自身位置，以利用局部温暖环境。本研究旨在探究龟类胚胎是否如同孵化后个体一般，主动寻觅适宜发育的热环境。具体而言，本研究设置两个核心问题：其一，爬行动物胚胎是否会远离极端高温，同时向温暖区域移动？其二，此类胚胎移动究竟源于主动体温调节，还是更直白地说，由局部热诱导的卵内流体黏度变化所引发的被动胚胎位移？我们针对泽龟科（Emydidae）中华草龟（Chinemys reevesii）开展的实验结果显示，胚胎可通过移动至卵内较凉爽区域，躲避极端高温。胚胎的位置调整属于主动过程而非被动过程：存活胚胎会向热源方向移动，而死亡胚胎则无此类移动。综合而言，本研究结果表明，龟类胚胎的行为体温调节属于主动过程，与孵化后的变温动物所表现出的体温调节行为确实高度相似。