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Reptile sex goes wild when things heat up, UC research finds
By Georgina Connery
Is it a boy or a girl? In the world of reptiles it is not so simple.
A University of Canberra-led research collaboration has discovered reptile's sex determination process can switch rapidly from one determined by chromosomes to one determined by temperature.
Temperature is a key factor in sex determination in reptiles.Credit: University of Canberra
The study, published on the cover of Nature, has proven climate-induced change of male bearded dragon lizards into females occurs in naturally occurring populations.
Using field data from 131 adult lizards and controlled breeding experiments the researchers conducted molecular analyses showing that some warmer lizards had male chromosomes but were actually female.
Bearded dragons with Dr Clare Holleley with University of Canberra Professor Arthur Georges.Credit: University of Canberra
"Their genetics say they are male, but their physical characteristics, their acting, living, behaving and reproducing like a female," Lead author Dr Clare Holleley said.
"We also found that sex-reversed mothers – females who are genetic males – laid more eggs than normal mothers. So in a way, one could actually argue that dad lizards make better mums."
Knowing more about the impact of temperature was essential in predicting the evolutionary responses to climate change and rising global temperatures.
One concern for the arid woodland and desert dwelling animal is whether exposure to more and more extreme summers might lead to a female bias in the population.
"If that goes to a complete extreme and there is no more males, then that is certainly a concern for the species and might lead to their extinction," Dr Holleley said.
Co-lead author Ira Deveson, a PhD student from the Garvan Institute of Medical Research in Sydney examined the messenger RNA molecule of sex-reversed female dragons, compared with normal male and female dragons.
"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."
"This means that the gene won't make a normal protein. Somehow that throws a spanner in the works when it comes to making a male," he said.
Even more surprising was the finding that the same gene retains this chunk in crocodiles and turtles. This suggests that temperature-determined sex depends on this "alternative RNA" in all reptiles.
The study's findings will likely spark a whole new approach to understanding sex determination in nature and move the scientific community closer to understanding the whole picture of sex.