Bearded dragons are one of the most fascinating species of lizard. Yet, there’s a strange thing going on with the species: the Australian lizards’ sex changes with global warming, as they are struggling to survive the constantly rising temperatures of the land Down Under.
But how does this biological oddity happen?
Sex reversal is the process by which the genetic sex of a being is reversed into the other one. The discovery of the process in bearded dragons was reported in Nature’s latest issue. Arthur Georges further explained the process by giving examples of what would happen in humans. An XY human being would normally be of the male gender, yet there might occur a mutation which invalidates the male gene on the Y chromosome.
In reptiles, sex change occurs when they are still incubating and is usually triggered by the temperature in the outside environment. If it’s too hot, the lizards usually reverse into male form. . It is the first documented case of such a process happening on reptiles and furthermore, the first case in which lizards, a specific group of reptiles, show that they can do this.
The team of researchers who discovered this among Australian bearded dragons is from the Institute of Applied Ecology in Caberra. Under the leadership of Georges, they analyzed field statistics belonging to 131 adult dragons that had been caught in the wild. The resulting data was compared with breeding experiments done under controlled conditions.
To their surprise, the scientists found the sex of eleven lizards had been reversed. That is, instead of having female chromosomes like their anatomical traits suggested, these eleven exceptions were male. The lizards have a ZZ – male, ZW – female chromosomal sex system, closely resembling birds. The sex reversed ones had only ZZ chromosomes.
Yet, the more interesting feature is this: being anatomically female, these dragons could still lay eggs. The only difference was that they could lay twice the number of eggs as a non-reversed female could, and that they subsequently became much better mothers, because they are much bigger and more robust.
One of the writers of the study draws attention that this is a worrying fact and that if climate change continues, it could mean the total disappearance of the W chromosome. Growing heat can also lead to the development of this condition in other animals, though scientists are pretty sure it won’t get to humans.
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