Extreme Heat Triggers Lizard Sex Change

Female bearded dragon lizards turn into males exposed to high temperatures while still in their eggs, scientists report.

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. [...]

"The evidence that nest temperatures can override sex chromosomes is absolutely clear-cut," he commented.

In the animal kingdom, sex is determined either by genes or by the temperature at which an embryo develops. The bearded dragon lizard, found in Australia, appears to be the first species in which environment overrides genes to determine sex.

"The work is exciting because it suggests that a long-held dogma in this research field—that in any given population, sex is determined by a single process—is now in tatters.

"The factors that determine an animal's sex are truly basic to its biology, and it's becoming increasingly clear that we don't really understand what those factors are, at least in some major groups of animals. "

Heat Triggers Sex Change in Lizards by "Turning Off" Key Gene [National Geographic]

Image: Kim S