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student researching turtles climate change

National Science Foundation Fellow Amanda Carter researches ‘Hot Babes, Cool Dudes,’ a phenomenon that may help turtles adapt to climate change.

‘Hot Babes, Cool Dudes’ phenomenon may help turtles adapt to climate change

It is often the excellence of Illinois State’s faculty that attracts students of high caliber, like Amanda Carter, a biology doctoral student in her third year.

Carter arrived at Illinois State as a National Science Foundation (NSF) Graduate Research Fellow. Those receiving the prestigious award can generally choose where they wish to pursue their doctorate. Carter chose the lab of Biology Professor Rachel Bowden.

“The people I met when I visited Illinois State and the science being done in Rachel’s lab really brought me here,” said Carter, who is originally from Richmond, Virginia.

Carter joined Bowden’s lab, specifically for research on turtles. Bowden is a leader in the study of red-eared slider turtles. Her lab has brought in more than $1 million in grants for research with graduate, doctoral, and postdoctoral students, such as Carter.

“Doctoral students are critical to the success of the School of Biological Sciences,” said Bowden. “I’m at ISU because I have the opportunity to work with doctoral students like Amanda.”

In Bowden’s lab, Carter studies whether turtles will have an advantage when it comes to climate change. Typically, the sex of a turtle is determined by the temperature of the sand or soil in which a mother lays the egg. Eggs laid in warm sand or soil produce female turtles. Cooler temperatures tend to produce males. The phenomenon has the nickname, “Hot Babes, Cool Dudes.”

Carter is exploring whether a mother turtle can give an extra boost of steroids to the turtle eggs that would tip the scales beyond temperature. When mother turtles lay eggs, they allocate steroids that can include adding a bit more estrogen. “So you can incubate an egg at a ‘male’ temperature, but if you add a dose of estrogen to the outside of the egg, it will produce a female,” Carter said.

This extra dose of estrogen may give turtles an edge when it comes to climate change. Changes in climate have shifted the temperatures of sands and soils where turtles nest. In her studies, Carter works to understand if mother turtles can help offset the variations in soil temperature.

“I’m looking at whether turtles have the potential to better respond to climate change via yolk estrogens, which may increase the range of temperatures that produce both male and female offspring,” she said.

Much of Carter’s field research is conducted at the Banner Marsh near Peoria, along the Illinois River. “I love fieldwork, so I try to plan to be out there as much as I can,” she said. Summer means traveling to the marsh from May to July to track females nesting and to gather eggs to incubate in the lab. “Turtles will lay two clutches of eggs in the nesting season, one early and one later, and we know that the clutches laid later in the season have higher levels of estrogen. So there might be a seasonal shift in the ratios of female to male as well,” she said.

Biology Professor Rachel Bowden turtles climate change

Illinois State Biology Professor Rachel Bowden

“Amanda’s work has the potential to provide important advances in our understanding of how a long-lived species may cope with rapid environmental change,” said Bowden. “Her decision to study how turtles respond to temperature fluctuations using a very common species will help inform how less common species may be able to respond to changing temperatures as are predicted under climate change models.”

A fascination with temperature-dependent sex determination (TSD) is what drew Carter to biology. And Bowden’s lab offered her the ideal chance to cultivate her love of science.

“There are several labs across the country that study TSD, but I knew I was interested in the hormone and physiological side of TSD, and not many labs are set up to do that,” said Carter. “So Rachel’s lab was really the perfect combination of science and my interests. Not to mention the fact that Rachel is wonderful.”

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