The sexes of many baby reptile are define by the temperature that the ball experience while being brood in the nest . What ’s more , lounge lizard in the laboratory have been bonk to switch to this temperature - dependent system from one in which sex activity is square up by chromosomes ( as in humankind ) . And now , research worker have discovered the earth ’s first naturally occurring case : Australian cardinal bearded dragon ( Pogona vitticeps ) are susceptible to climate - get sex reversal in the wilderness , according to findings published inNaturethis workweek .
Human females have two hug drug chromosome , while males have an X and a Y. This is flipped with Australian whiskery dragons : Females have a izzard and a W , while males have two Z chromosomes . But while ZW lizards are always females , ZZ lizards could become either sex . Previous experiments find that high brooding temperature “ feminize ” chromosomally male lizards , producing so - call “ sexual practice reversed ” females ( ZZf ) . How do dissimilar sexuality purpose systems coexist in climate - sore reptiles , and what triggers the switch between them ?
A squad led byClare Holleley from the University of Canberracollected rear end snips and blood from 131 wild grownup lizard live in widely distributed populations of semi - desiccate Australia . With molecular analyses , they name that 11 of those lizards – found toward the warm end of the species ’ range – had a male set of chromosome but were female ( that is , they lacked the partner off genitals known as hemipenes ) . These lizards had undergo a rapid transition from a genetically - controlled organization to one that ’s dictated by temperature .
Then the team match sex activity - reversed ZZf female person ( include both wild - see as well absorbed - bred females ) with ZZ males . Their offspring were viable and fertile and , as expected , the W sex chromosome was egest . Their sex was only find by egg brooding temperature , which crop from 26 up to 36 level Celsius . In the absence seizure of a W chromosome , female young are only possible via sex reversion . While low incubation temperatures of 28 level Celsius produced all male ZZ hatchling , by 34 level Celsius , the offspring were preponderantly female ZZf hatchlings .
what is more , with “ normal ” ZW females , temperature began to reverse chromosomal sexual activity determination – and cause sexual practice turn around – from above 32 degrees Celsius , resulting in an increasing proportion of female hatchling as temperature rose . to boot , offspring of sex - invert ZZf mothers are also more predisposed to annul , reinforcing the transition . Also , sex - reversed mother lay nearly twice as many eggs per year as control ZW mothers – which may extend to an excess of females in the universe .
The finding suggests that mood extremes might alter lizard genome , although perhaps being more elastic with sex determination could prove to be useful as the mood becomes more unpredictable .
Images : Arthur Georges
