Hot temperatures are changing the gender of lizards, study finds – Science

The cold-blooded Australian Central Bearded Dragon is widespread on red sandy areas in the semi-arid regions of eastern Australia.

The researchers showed that by incubating the bearded dragon’s eggs in very warm temperatures (above 89.6 degrees) you can trigger them to reverse sex.

When the sex-reversed females mated with “normal” male lizards, the sex of the offspring was entirely determined by egg incubation temperature, rather than chromosomes.

MORE: It’s official – this is the hottest day of the year so far (and the hottest July day ever!). The lizards are doing this in a somewhat unusual way: They’re switching genders in a move that has been linked with increasing temperatures, researchers from the University of Canberra say in a release.

“If you’re a he-she animal – with male sex chromosomes, but reproducing as a female – you actually laid nearly twice as many eggs as a regular female”, Hollely said.

Clare Holleley, of Canberra University, said the finding adds to worries about how creatures will adapt to rapid global climate change. The team of scientists has performed the study on 131 adult lizards, by controlled breeding experiments.

The lizards can reproduce and fully functional as female but their physical appearance is male. In time, the male chromosome could disappear, as more and more females are bred – the preferred sex. The sex chromosomes of these reptiles, like birds, are Z and W. The males have ZZ, while the females ZW. For the bearded dragon, everyone has a Z and the female gender is determined by the presence of a W.

This actually is the “first report of reptile sex reversal in the wild”, and shows that other lizards could also be affected. Even though their chromosomes are telling them to be male, the heat makes many ZZ embryos grow up as females. “They’ve completely lost a whole chromosome in one generation”, says Holleley.

According to the authors of the study, the lizards who exhibited sex reversal were better mothers than the genetic females.

It’s the first time we’re seeing two separate systems of sex determination, thought to be separate by an evolutionary gulf, in mid-switch.

The climate changes caused by global warming affects the entire lizard population in such a way that the sex of the lizards may no longer be determined by the genetic signals of chromosomes, but by the temperature.


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