Turtle embryos have some say in their own sexual destiny: they can move around inside the egg to find different temperatures, a study by Chinese and Australian researchers shows.
Scientists had already shown that the temperature of the turtle egg determines whether they develop as male or female in some species, but the new study finds that embryos can play a role in determining their own sex by adjusting those temperatures.
The study, published in the journal Current Biology on Thursday, examines how this behaviour may help turtles offset the effects of climate change, the researchers said in a statement.
"We previously demonstrated that reptile embryos could move around within their egg for thermoregulation, so we were curious about whether this could affect their sex determination," Wei-Guo Du, the study's corresponding author and professor at the Beijing-based Chinese Academy of Sciences, said in the statement.
"We wanted to know if and how this behaviour could help buffer the impact of global warming on offspring sex ratios in these species," he added.
The researchers incubated turtle eggs at various temperatures in outdoor ponds and laboratory conditions, finding that embryos could experience a temperature difference of up of 4.7 degrees Celsius in the egg.
Du said any shift larger than 2C can massively change the sex of the offspring in many turtle species. The proportion of females hatched rises with warmer temperatures.
"The most exciting thing is that a tiny embryo can influence its own sex by moving within the egg," Du said.
To prove their findings, the researchers applied a chemical, called capsazepine, that blocked temperature sensors in half of the eggs to prevent thermoregulation.
They found the embryos without thermoregulation were hatched as almost all males or almost all females, depending on the incubation temperatures. Embryos without the chemical reacted to conditions in the nest and were able to move around inside their eggs.
By moving around, the embryos were able to find the neither too hot, nor too cold "Goldilocks Zone", said Richard Shine, a co-author and professor at Sydney's Macquarie University. About half of them developed as males and the other half as females.
The findings may explain how species that experience this temperature-dependent effect have survived periods in earth's history where temperatures were a lot hotter than they are now, Shine said.
But there are limitations. Du said much more rapid climate change could still cause severe female-biased populations among some species of turtles. Researchers still plan to explore how embryos and mothers will try to buffer the impact of climate warming going forward.
Last year, scientists published a study in the same Current Biology journal saying that warming ocean temperatures, linked to climate change, resulted in 99 per cent of green sea turtle eggs producing females in the northern region of Australia's Great Barrier Reef.
Australian Associated Press
