Dr. Thane Wibbels (University of Alabama at Birmingham) is interested in studying how temperature affects the sex of red-eared slider turtle embryos. For humans, the answer is simple: sex chromosomes. You know, the combination of XX means girl and XY means boy.
Turtles are not that simple. Temperature is a factor in determining whether the embryo will be male or female. If the eggs are incubated at 78.8 degrees F, the hatchlings will all be male. If they are incubated at 87.8 degrees, they will all be female. As I’m sure you’ve guessed, temperatures in between these points will result in a mixture of female and male hatchlings. This temperature-based sex determination is a reptile trait that is speculated to date as far back as 220 million years ago.
A new study published by Drs. Wibbels and Kayla Bieser (Northland College, Ashland, Wisconsin) in the journal Sexual Development tried to understand this mystery. They examined the expression of 5 genes in turtle eggs exposed to either 78.8 or 87.8 degrees. They discovered that a gene called dmrt1 is the earliest gene to be expressed in males and according to Dr. Wibbels, this gene in particular seems to be involved in male sex determination for all vertebrates. The plan now is to find the “male producing” switch that dmrt1 turns on.