Study proves turtle embryos move themselves within shells to exploit best temperature conditions

Jun 12, 2013 by Bob Yirka report
The position of embryonic Chinese pond turtles (C. reevesii) inside eggs, as shown by candling. The arrow indicates the site that we used to score embryonic position within the egg: the point where the neck joins the carapace. Credit: Biology Letters, Published 12 June 2013 doi: 10.1098/rsbl.2013.0337

( —A team of researchers working in China has proven that the three-keeled pond turtle embryo is capable of moving itself towards or away from a heat source in order to warm itself or cool down. In their paper published in the journal Biology Letters, the team describes how they subjected turtle embryos to various heat scenarios while monitoring their movements inside their shells to show that the turtles were directing their own actions while still inside their eggs.

, as most are aware, are cold-blooded animals. They regulate their body temperature by moving themselves to warmer or cooler places. In this new study, the researchers found the same ability applies to turtles while still in their shell.

have known since 2011 that at least some turtle move about in their shell in response to external heat sources. Another team in China had discovered this ability and had published a paper describing their results. What that team wasn't able to say for sure, though, was whether the turtle embryos were moving themselves or if fluids within the shell were causing the movement. In this new effort, the research team sought to find the answer to that question.

The team set 125 (in groups of five) in incubators set at 26 °C. Then four of the five groups were subjected to various degrees of heat applied at one end of the eggs. The team also set up bright lights next to the eggs that allowed them to see the silhouettes of the embryos inside as they moved. In all but the , the team observed that the embryos moved away from the , thus confirming the findings of the team in 2011.

To ascertain whether the embryos were moving themselves or were simply being carried by heated fluid, the researchers ran another similar experiment. This time they allowed 41 embryos to develop naturally for ten days, whereupon, they killed half of them using an injected chemical. After applying heat and waiting for a week, they cracked open the eggs and found that only those turtle embryos still alive had moved away from the source. This they claim, proves that the embryos moved themselves intentionally.

The researchers noted also that the ability to move inside the egg may also be a means of allowing the embryos to choose their own gender—previous studies have shown that temperatures during incubation can determine whether turtles are born male or female.

Explore further: Research helps steer mites from bees

More information: Turtle embryos move to optimal thermal environments within the egg, Published 12 June 2013 doi: 10.1098/rsbl.2013.0337

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.

Related Stories

Turtle embryos move to bask in the sun

May 25, 2011

( -- Turtles, like the majority of reptiles, are unable to regulate their own body heat and use their environment to control their temperature. In order to stay warm, reptiles will bask in this ...

Evolutionary origin of the turtle shell

May 30, 2013

Through careful study of an ancient ancestor of modern turtles, researchers now have a clearer picture of how the turtles' most unusual shell came to be. The findings, reported on May 30 in Current Biology, help t ...

Ban turtle eggs trade in Malaysia: WWF

Aug 03, 2011

Conservationists Wednesday urged Malaysia to impose a national ban on the trade and consumption of turtle eggs to ensure the survival of the marine creatures.

Recommended for you

Research helps steer mites from bees

22 hours ago

A Simon Fraser University chemistry professor has found a way to sway mites from their damaging effects on bees that care and feed the all-important queen bee.

Bird brains more precise than humans'

22 hours ago

( —Birds have been found to display superior judgement of their body width compared to humans, in research to help design autonomous aircraft navigation systems.

User comments : 0