The findings were published on 18 Dec in British journal Scientific Reports. The study marks the first time a molecule that links temperatures with sex has been identified.
The group, including researchers from the National Institute for Basic Biology (NIBB), already knew that when crocodiles raise their eggs at 33.5 degrees, they all become male, and at 30 degrees they become female. Most tortoises and some lizards develop in the same way.
But how eggs perceive the temperatures that determine the sex had been unknown until now.
Shinichi Miyagawa, 37, an associate professor, said: “The decision of sexes is a root of biodiversity of living creatures. But we wanted to know why the sexes of crocodiles are decided by temperature, which is an unstable factor.
“We have clarified part of the mechanism behind it. The result will be useful for the preservation of species amid growing concern over the effects of global warming.”
The team, also including Ryohei Yatsu, 26, a graduate school student, focused their research on the TRP protein which animals perceive temperatures with.
This led to the finding that a gene, TRPV4, works actively in reproductive glands at around 34 degrees, leading to the development of male crocodiles.
Then, the group administered a medicine which inhibits the effectiveness of TRPV4 to about 90 eggs from wild American alligators, a type of crocodile, and investigated their sexes.
As a result, it found that 45 percent of the eggs with the TRPV4 gene weakened by the medicine became female even when raised at temperatures at which crocodiles usually become male.
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