Bearded Dragon Sex

A new study out of Australia says that bearded dragon gender is determined by a combination of genes and temperature. Under normal conditions gender will be determined by genes, much like in humans. However if the eggs reach a temperature above a certain threshold then embryos can actually switch sex in the egg and lean towards being heavily female by the deactivation of one of the sex-determining genes.

It had previously been assumed that an animal's gender could be determined either by genes or by temperature as an embryo develops but not by both.

In the case of the central bearded dragon, it appears that temperature can override genes that trigger male development.

The study is reported in the current issue of the journal Science.

Heat Deactivates Sex Gene

Eggs incubated at higher than normal temperatures of 93.2 to 98.6 degrees Fahrenheit (34 to 37 degrees Celsius) produced a strong bias toward female hatchlings, which outnumbered males by about 16 to 1.

The researchers linked this gender bias to a sex-determining gene that was deactivated when the lizards' nests became unusually warm.

This process results in female offspring, because the key gene was discovered on the so-called Z sex chromosome, of which male lizards have two and females only one.

Deactivation of the gene therefore turns a male (ZZ) into a female (WZ).

This is a very interesting finding. It really will revolutionize the way biologists look at sex determination, especially in reptiles and maybe even in birds.

Photo used under creative commons license: Schilling 2