Wisconsin Sea Grant Frogs: Cool Science
Why Study Frogs?
page 2

Bill Karasov, a UW-Madison Professor and Wisconsin Sea Grant researcher interested in wildlife toxicology (the study of how toxins in the environment affect wildlife) talks about how PCBs affect frogs.

Deformed and missing limbs of frogs -- observed in widely separated regions of the world recently -- appear not be caused by environmental PCBs, according to the work of University of Wisconsin Sea Grant researcher William Karasov. Karasov has been examining the effect of PCBs on green and leopard frog reproduction along the Fox River and around Green Bay, Lake Michigan.

Karasov, a wildlife ecologist at the University of Wisconsin, Madison, and his students put healthy eggs into enclosures along the river and around the lower bay. Then they measured PCB levels in the animals' tissues. They found that tissue levels of PCBs were fairly low -- much lower than fish in the area typically exhibit. In fact, laboratory experiments show that deformities in anurans -- the order of amphibians that includes frogs and toads -- don't occur until levels are about 10 times higher than those found in the field.

"These are some of the first data gathered on the sensitivity of anurans to PCBs," Karasov said. "They appear to be relatively insensitive to PCBs." More controlled experiments in Karasov's laboratory showed similar results.

The data have practical implications. "They suggest that the regulatory guidelines established to protect fish will also protect amphibians," Karasov said. He said the results will also help predict toxicological effects at other locations.

Karasov and his students are now testing whether the development of anuran sexual organs occurs normally amid typical environmental PCB concentrations.

- originally printed in Sea Grant Communicator, Spring 1999





copyright 2001 University of Wisconsin Sea Grant Institute


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