活胚胎始终朝着温暖点移动，却避开了危险的过热温度点。图片来源：《科学》
冷血动物一生都在它们的栖息地中走来走去，像喜光的金凤花一样寻找完美的温度。但若它们生存于一只蛋中会发生什么呢？
科学家之前曾观察到甲鱼胚胎会朝其蛋中的温暖点移动，但他们并不能解释该运动是有意的还是被动的、是否由流体动力学所驱使。因此一队研究人员决定进行实验。他们在不同的温度下孵化了125只中华草龟蛋，并在蛋中创造过热、过冷和正好的温度点。图中的活胚胎始终朝着温暖点移动，却避开了危险的过热温度点。研究人员日前将报告在线发表于《生物学通讯》上。
同时，死亡胚胎一点都没有移动，说明活胚胎的活动是有一定的意向性的。由于孵化温度的轻微差别会决定乌龟的性别，因此胚胎本身可能对将其变成雄性草龟还是雌性草龟有一定的控制力。（生物谷Bioon.com）
生物谷推荐英文摘要：
Biology letters Doi: 10.1098/rsbl.2013.0337
Turtle embryos move to optimal thermal environments within the egg
Bo Zhao1,2, Teng Li1, Richard Shine3 and Wei-Guo Du
A recent study demonstrated that the embryos of soft-shelled turtles can reposition themselves within their eggs to exploit locally warm conditions. In this paper, we ask whether turtle embryos actively seek out optimal thermal environments for their development, as do post-hatching individuals. Specifically, (i) do reptile embryos move away from dangerously high temperatures as well as towards warm temperatures? and (ii) 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 rather than passive process: live embryos move towards a heat source, whereas dead ones do not. Overall, our results suggest that behavioural thermoregulation by turtle embryos is genuinely analogous to the thermoregulatory behaviour exhibited by post-hatching ectotherms.
