A Little Yolk for Boys
It's long been known that nest temperature influences the sex determination of reptile embryos. Now a study in Current Biology finds that, for alpine lizards, smaller yolks lead to males. Karen Hopkin reports
SUBSCRIBE TO Science Quickly
On supporting science journalism
If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.
[The following is an exact transcript of this podcast.]
When it comes to lizard sex, size does matter. But not in the way you might think. Because in the June 4th online issue of the journal Current Biology, scientists say that for at least one type of lizard, larger eggs are more likely to make girls while smaller eggs yield boys.
For many animals, the sex of an individual is dictated solely by its chromosomes. But for small alpine lizards, gender isn’t so cut-and-dried. The scientists had earlier found that nest temperature can influence the sex of lizard hatchlings. Cooler nests turn out more boys—no matter what their chromosomes say. At the same time, the researchers noticed that larger eggs seemed to make more daughters. But they wanted to put their observation to the test. So they took big eggs and removed some yolk—and, voila, they made males. Adding yolk to a little egg was a recipe for a female.
This size manipulation might allow moms to balance their babies’ sexes when a chilly nest would otherwise produce mostly sons. Because when it comes to alpine lizards, sex determination all comes down to a practical yolk.
—Karen Hopkin
It’s Time to Stand Up for Science
If you enjoyed this article, I’d like to ask for your support. Scientific American has served as an advocate for science and industry for 180 years, and right now may be the most critical moment in that two-century history.
I’ve been a Scientific American subscriber since I was 12 years old, and it helped shape the way I look at the world. SciAm always educates and delights me, and inspires a sense of awe for our vast, beautiful universe. I hope it does that for you, too.
If you subscribe to Scientific American, you help ensure that our coverage is centered on meaningful research and discovery; that we have the resources to report on the decisions that threaten labs across the U.S.; and that we support both budding and working scientists at a time when the value of science itself too often goes unrecognized.
In return, you get essential news, captivating podcasts, brilliant infographics, can't-miss newsletters, must-watch videos, challenging games, and the science world's best writing and reporting. You can even gift someone a subscription.
There has never been a more important time for us to stand up and show why science matters. I hope you’ll support us in that mission.
