Lizards will change their sexes

Arthur Georges

When some lizards can’t take the heat, they change sexes. In a recent study published in Nature, researchers in Australia revealed that rising temperatures are causing male Australian Bearded Dragons to change into females when developing in the egg. Not only that, but they make better mothers, laying more eggs than naturally born females.

Prior to this discovery, it was believed that some reptiles, such as crocodiles and certain types of lizards and turtles have temperature-dependant sex determination (TSD), while others, like some lizards and turtles, and all snakes, have genotypic sex determination (GSD).

“TSD species were thought to be particularly vulnerable to climate change and GSD species secure,” study co-author Arthur Georges of the University of Canberra told “I suppose what our work means is that, firstly, TSD and GSD are not that far apart mechanistically or in evolutionary terms, which is contrary to mainstream thinking. Secondly, it means that even GSD species can be vulnerable to climate change because higher temperatures can make them switch to TSD.”

Bearded dragons typically inherit two sex chromosomes — ZZ for the males and ZW for the females. After bringing in 131 specimens from the wild, George and Dr. Clare Holleley conducted controlled breeding experiments using a variety of cutting edge techniques, including comparative genome hybridization to demonstrate sex reversal. They also used a bacterial artificial chromosome (BAC) library.

“We used a bacterial artificial chromosome library to generate and verify sex specific sequence and probes that were important to determine the underlying sex of individuals,” Georges said. “A BAC library is constructed by cutting up the dragon DNA, the whole genome, and inserting the fragments into bacterial colonies, one fragment per colony, so you can pull particular dragon sequence out at will.”

Pablo Dorador Ontiveros

Dulce María Sáez Martínez

Jesús Sánchez García



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