Researchers discover how temperature affects the sex of reptiles

By AG Staff June 16, 2017
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For fifty years scientist have tried to understand what part of reptiles molecular anatomy determines their sex. Now a team of researchers from the University of Canberra have found the ‘master switch’.

RESEARCHERS HAVE DISCOVERED a molecule in Australia’s bearded dragon lizard that is sensitive to temperatures, making it the ‘master switch’ in the sex selection process in reptiles.

In humans and other mammals, sex chromosomes determine physical sex. However in reptiles, sometimes sex chromosomes do not match physical sex. This is known as sex reversal. Their sex is determined by the temperature their eggs are incubated at. 

For the past fifty years scientists have attempted to understand what part of the reptiles’ molecular anatomy causes this change in sex.

Yesterday a team of researchers from the University of Canberra published their findings in the journal, Science Advances, which will ultimately change the way sex selection is understood in animals.

“We think our discovery will spark a whole new approach to understanding how to make males and females – in all animals,” said Jenny Graves, a professor at La Trobe who collaborated on the research.

The team of researchers studied the Ribonucleic acid (RNA) molecules of bearded dragon lizards that were functional females, but genetically male, and then compared these to molecules with RNA made by normal males and normal females.

“The dragon lizard has sex chromosomes similar to birds that determine sex at normal temperatures. But at high temperatures, embryos with male sex chromosomes reverse sex and hatch as females,” said Clare Holleley, a research scientist from the CSIRO and lead author of the paper.

Clare told the ABC that once temperatures reached up to 36 degrees during incubation, 100 per cent of the offspring will be female.

“We found that sex-reversed females produce a unique message with their RNA retaining a chunk of sequence that is normally spliced out of the message.”

The hot temperatures that have been found to result in 100 per cent female offspring suggest that climate change can pose a significant threat to certain populations of reptiles.

“It means you’re at a risk, if it’s too hot, of having all the offspring come out the same sex,” Clare told the ABC, who hopes to focus future research on the impact of stress on the sex selection process.