As Embryos, Turtles Can Choose Their Own Gender, Study Says

New research from a team at the Chinese Academy of Sciences in Beijing suggests that turtle embryos move around within their eggs to regulate their body temperature, effectively allowing them to choose their gender.

The find upends a long-held belief that the environment in which the mother turtle lays her eggs is the sole factor in gender determination in turtles, Nature reported.

"Our results suggest that animals may actively select their own destiny even at the very early stage of embryos," said Wei-Guo Du, an ecologist at the Chinese Academy of Sciences and leader of the research team.

For many species of turtles, embryos developing in cooler conditions are primarily born male, whereas embryos developing in warmer conditions are mainly female.

Du's research built upon prior work suggesting turtle embryos will move from cooler to warmers areas within their eggs, demonstrating turtles are responsive to heat as well and will seek cooler areas within the egg when exposed to extremely high temperatures. In a laboratory, Du and his colleagues subjected turtle eggs to temperatures as high as 33 degrees Celsius.

Research published last month on the North American painted turtle suggested that the species may be on its way toward extinction due to global warming, with more female turtles beign born as temperatures continue to increase, leading the species exposed to a lack of breeding partners.

But it's unlikely that turtles will be able to save themselves from global warming.

"The behavior may buffer climate change effects but only to a certain degree," George Parsons, senior director of the Fishes Department at the John G. Shedd Aquarium in Chicago, told Nature.

Ecologist Fredric Janzen is skeptical about whether Du's laboratory findings would also hold true in the wild, noting that temperature-dependent gender determination is influenced by a variety of other factors including the overall climactic temperature, vegetation covering the nests and yolk steroid hormone levels.

"That doesn't seem to leave much 'room' for this embryonic thermoregulation mechanism, if it is general among turtles, to have a substantive effect on offspring sex determination," Janzen told Nature.

Du and his colleagues' research is published in the journal Biology Letters.