New Discovery Uncovers the Mechanism Behind Temperature’s Influence on Turtles’ Sex Determination

A freshwater turtle called a red-eared slider. Credit: Wikimedia Commons

Warmer temperatures are known to influence the sex of turtle hatchlings, with more eggs developing into females. However, researchers at Duke University have discovered that these female hatchlings also exhibit a higher capacity for egg production, even before their sex is determined.

This new finding might explain why other animals also have temperature-dependent sex determination and why this system continues to exist despite its risks. Additionally, it provides insight into the potential consequences of a warming world.

Published in the journal Current Biology on June 23, the study revealed that higher incubation temperatures increase the number of “germ cells” – pre-eggs – an embryo carries. These germ cells play a role in determining the embryo’s sex, suggesting that sex determination by temperature involves multiple cell types in the embryo.

Boris Tezak, the postdoctoral researcher who led the project, explained that the more germ cells an embryo has, the more likely it is to develop into a female. Similar to fish, where germ cells control female development, the removal of germ cells from red-eared slider embryos resulted in a higher number of males than expected.

Temperature-dependent sex development has been observed across various species, indicating that it has evolved numerous times in different ways. Despite its apparent risks, the researchers believe this system persists because it offers a reproductive advantage.

“A female that hatches with more germ cells is presumably more reproductively fit—it increases her reproductive potential to carry more eggs,” Tezak said. “We’ve linked the female pathway to the increased number of germ cells, and if that does make her more reproductively fit, that would go a long way toward explaining why temperature-dependent sex development persists.”

As global temperatures continue to rise, it raises concerns about the impact on temperature-sensitive breeders like turtles. Tezak plans to investigate how further temperature increases affect the pool of germ cells and whether it produces less-fit females.

To study these questions, Tezak nurtures clutches of red-eared slider eggs in controlled environments. One incubator produces more males at 26 degrees Celsius, while another at 31 degrees produces more females. The researchers also plan to conduct temperature experiments using alligator eggs, as alligators exhibit the opposite pattern of sex determination.

The research conducted by Duke University sheds light on the intricate relationship between temperature and the sex of turtles, providing valuable insights into the potential impacts of climate change on these species.

More information:
B. Capel, Higher temperatures directly increase germ cell number which promotes feminization of red-eared slider turtles, Current Biology (2023). DOI: 10.1016/j.cub.2023.06.008. www.cell.com/current-biology/f … 0960-9822(23)00758-3

Provided by Duke University

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New finding suggests how and why temperatures determine the sex of turtles (2023, June 23)
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