In lizards, egg size matters

SYDNEY, June 9 (UPI) -- Australian scientists have discovered that for at least one lizard species, whether baby lizards are male or female depends upon the size of the egg.

"We were astonished," said Richard Shine of the University of Sydney. "Big eggs tend to give girls and small eggs tend to give boys. And if you remove some of the yolk just after the egg is laid, it's likely to switch to being a boy, even if it has female sex chromosomes; and if you inject a bit of extra yolk, the egg will produce a girl, even if it has male sex chromosomes."

Shine said the findings add to evidence that when it comes to genetic versus environmental factors influencing sex determination, it doesn't have to be an either/or proposition.

He said he thinks there will be much more to discover when it comes to lizard sex determination.

"I suspect that the ecology of a species will determine how it makes boys versus girls, and that our yolk-allocation effect is just the tip of a very large iceberg," he said.

The study, which included Rajkumar Radder and David Pike of the University of Sydney and Alexander Quinn of the University of Canberra, appears in the online edition of the journal Current Biology.