Toastier nest temperatures, rather than sex chromosomes, turn baby turtles female. Now, a genetic explanation for how temperature determines turtles’ sex is emerging: Scientists have identified a temperature-responsive gene that sets turtle embryos on a path to being either male or female. When researchers dialed down that gene early in development, turtle embryos incubating at the cooler climes that would normally yield males turned out female instead, researchers report in the May 11 Science.
Scientists have struggled since the 1960s to explain how a temperature cue can flip the sex switch for turtles and other reptiles (SN Online: 1/8/18). That’s partly because gene-manipulating techniques that are well-established in mice don’t work in reptiles, says study coauthor Blanche Capel, a developmental biologist at Duke University School of Medicine. Previous studies showed certain genes, including one called Kdm6b, behaving differently in developing male and female turtles. But until recently, nobody had been able to tweak those genes to directly test which ones controlled sex.