original text: http://dailynews.yahoo.com/h/nm/20010815/sc/science_lizards_dc_1.html

Wednesday August 15 2:16 PM ET

Lizards Might Choose Offspring's Sex by Sunbathing

By Mike Collett-White

LONDON (Reuters) - Lizards might be able to control the sex of their offspring by getting more or less sun and regulating the temperature during gestation, scientists said on Wednesday.

It is not yet clear whether the choice of temperature is deliberate, but one theory is that the cold-blooded reptiles use temperature to control the number of male and female offspring and maintain a balance between sexes in the adult population.

Alternatively females of the Australian skink species known as Eulamprus tympanum might opt for warmer temperatures, and therefore male offspring, whenever they can as it speeds up gestation, although the mountain terrain they inhabit limits their choice.

``Given the opportunity in captivity, pregnant female Eulamprus tympanum will bask at higher temperatures which speed up embryogenesis, and hence reduce their burden, and produce male offspring,'' said Kylie Robert of the University of Sydney, Australia.

But in the wild the lizards produce balanced litters.

Robert said that factors such as cool weather or the presence of predators may prevent the lizards from reaching warmer temperatures.

Alternatively, they might actively choose to maintain lower temperatures to produce balanced litters.

Future research will concentrate on maintaining the lizards in balanced and unbalanced populations to examine whether they alter the sex of their offspring in response.

Robert said the findings of the study pointed to potential problems for the species if global warming caused a further increase in temperatures.

``Eulamprus tympanum is already restricted to mountain tops and with a four degree Celsius rise, as predicted by global warming models, they cannot retreat to cooler regions,'' she said.

``This means in turn they would produce male offspring and eventually extinction is a high possibility,'' she added.