Boy or girl? In lizards, egg size matters

Jun 04, 2009

Whether baby lizards will turn out to be male or female is a more complicated question than scientists would have ever guessed, according to a new report published online on June 4th in Current Biology. The study shows that for at least one lizard species, egg size matters.

"We were astonished," said Richard Shine of the University of Sydney. "Our studies on small alpine have revealed another influence on lizard sex: the size of the egg. Big 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 ; and if you inject a bit of extra yolk, the egg will produce a girl, even if it has male sex chromosomes."

In many animals, the sex of offspring depends on specialized sex chromosomes. In mammals and many reptiles, for instance, males carry one X and one Y chromosome, while have a pair of X chromosomes. In contrast, animals such as alligators depend on environmental cues like temperature to set the sex of future generations.

The new 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. In fact, Shine and his colleagues earlier found in hatchlings of the alpine-dwelling Bassiana duperreyi that extreme nest temperatures can override the genetically determined sex, in some cases producing XX boys and XY girls. His group had also noticed something else: large lizard eggs were more likely to produce daughters and small eggs to produce sons.

Despite the correlation, Shine said he had assumed that the association was indirect. In fact, his colleague Rajkumar Radder conducted studies in which he removed some yolk from larger eggs, more likely to produce daughters, to confirm that assumption.

"We were confident that there would be no effect on hatchling sex whatsoever," Shine said. "When those baby boy lizards started hatching out, we were gob-smacked."

Shine 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.

Source: Cell Press (news : web)

Explore further: Keep dogs and cats safe during winter

add to favorites email to friend print save as pdf

Related Stories

How do you know whether you are male or female?

Dec 27, 2007

New research published online this week in the open-access journal PLoS Biology investigates this basic and much-studied question in the fruit fly, and comes to a surprising new conclusion.

Boy or girl? It's in the father's genes

Dec 11, 2008

(PhysOrg.com) -- A Newcastle University study involving thousands of families is helping prospective parents work out whether they are likely to have sons or daughters.

Children's sex affects parents' marital status

May 23, 2006

Parents with a boy and a girl are more likely to stay married, or get married if they were unmarried when their children were born, than those with two boys or two girls according to new research from ANU economist Dr Andrew ...

Female birds boost up their eggs when hearing sexy song

Jun 08, 2006

In a new study published in the latest issue of Ethology researchers show that female songbirds can alter the size of eggs and possibly the sex of their chicks according to how they perceive their mate’s quality.

Female Birds Boost Up Their Eggs When Hearing Sexy Song

Jul 17, 2006

In a new study published in the latest issue of Ethology researchers show that female songbirds can alter the size of eggs and possibly the sex of their chicks according to how they perceive their mate's quality. The resear ...

Recommended for you

Keep dogs and cats safe during winter

Dec 27, 2014

(HealthDay)—Winter can be tough on dogs and cats, but there are a number of safe and effective ways you can help them get through the cold season, an expert says.

Scientists target mess from Christmas tree needles

Dec 26, 2014

The presents are unwrapped. The children's shrieks of delight are just a memory. Now it's time for another Yuletide tradition: cleaning up the needles that are falling off your Christmas tree.

The ants that conquered the world

Dec 24, 2014

About one tenth of the world's ants are close relatives; they all belong to just one genus out of 323, called Pheidole. "If you go into any tropical forest and take a stroll, you will step on one of these ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.