ATHENS, Ohio -- Researchers at Ohio University are studying deformed frogs found at a pond in Southeastern Ohio, trying to determine if the deformities are caused by a naturally occurring parasite, chemicals used in a nearby cornfield or some other phenomenon.
Researchers studying the pond in Lancaster, about 30 miles from Columbus, have found that about 5 percent of the frogs have some sort of deformity, said James Barron, an assistant professor of biological sciences at Ohio University's Lancaster campus. Scientists at the National Institute of Environmental Health Sciences say it's normal to find a small number of deformed frogs -- 1 percent -- at any given site.
"The incidence of these deformities in Ohio appears to be low, but the numbers are sufficient enough to warrant investigation," said Barron, who is coordinating all Ohio reports of amphibian malformations for the North American Reporting Center for Amphibian Malformations, a project of the Biological Resources Division of the U.S. Geological Survey.
While the frogs collected from Lancaster are the only ones currently under study by Ohio University researchers, Barron also plans to investigate reports of amphibian malformations he's received this fall from Hamilton, Franklin, Madison and Coshocton counties.
"I've been aware of the problem in other states, but this gives us a unique opportunity to examine the problem in Ohio," Barron said.
National reports of deformed frogs date back to the 1700s, but the number of reports have increased dramatically since 1995. The largest deformed frog populations have been found in Wisconsin, Minnesota and parts of Canada. In these areas, reports suggest that anywhere between 10 and 75 percent of specific species of frogs have deformities.
Researchers at Ohio University first heard of the frogs in Lancaster from a local family that discovered a frog with five extra legs growing from its sternum. After documenting the case, Barron sent the bullfrog, nicknamed Lefty, to researchers at the National Wildlife Center in Madison, Wisc., for further study.
Working with biological sciences graduate students Shala Hankison and Wade Winterhalter, Barron collected deformed bullfrogs and green frogs from the pond in Lancaster. Hankison, who has done earlier research on frogs, will spend the next several months studying the frogs and water and soil samples collected from the site.
"There are several hypotheses about the causes of frog deformities, and I'll examine each to see what may have caused the problems here," Hankison said.
One hypothesis is that amphibian deformities are caused by a naturally occurring parasite, called a trematode, which alters limb development by burrowing into the limb buds of tadpoles. While this may hold true for some of the frogs the researchers collected, it most likely isn't the cause of all the deformities, Hankison said.
"Lefty's deformity is an extra leg growing from its sternum, and there's no way a trematode could cause a limb to grow there. That is more of a developmental deformity," she said.
Some scientists believe pesticides are to blame for the growing number of amphibian malformations, and Hankison says that is a possibility in this case. The frogs were found in a pond bordering a cornfield that was subjected to a new tilling technology using a lot of herbicides.
"When we study the water and soil samples, we should have some answers about herbicides," she said.
Still another hypothesis is that deformities are caused by exposure to ultraviolet radiation caused by holes in the Earth's ozone layer, but Barron says recent research casts doubt on that possibility.
It's likely there is no one cause of the frog deformities the researchers here will be studying, since the deformities range from extra limbs to too few limbs to facial deformities. And, Barron added, investigations of deformed frogs in other counties may reveal an even broader range of malformations.
Materials provided by Ohio University. Note: Content may be edited for style and length.
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