By Dan Shapley
Frog Deformities Are Probably Not Toxic Radioactive Freaks By Dan Shapley News Editor
The discovery of a nine-legged frog
in a Kansas landfill could ignite an old scientific controversy. It has already alarmed local parents. About 10 years ago, reports of deformed frogs had the public â and the scientific community â worried that chemicals, radiation or some other malevolent force was causing some frogs to grow extra limbs, and others to have them go missing. The attention to the problem made more people look, which made more people find deformed frogs, which made the problem seem as if it was growing. But years of research into the problem, according to one of the nation's leading experts on the issue, have pretty well hammered out the main cause: A common parasite. Here we go again! Stanley Sessions, Ph.D., said when he heard about the latest frog scare. By now we have definitive proof (or as close as you can get to it) that frogs with extra legs are caused by a parasite, and not by chemical pollution, the Hartwick College (Oneonta, N.Y.) professor and frog deformity expert wrote in an email to The Daily Green. There has been publication after publication showing this to be true. The offending parasite is a trematode, or flatworm. The particular buggers responsible for all those deformed frogs live complex lives that include spending their adulthoods in birds and their young lives in snails. In between, they stop over in frogs and tadpoles. While there, the trematodes cause cysts in developing tadpoles, and the cysts mechanically rearrange the cells, causing the sprouting of legs in all the wrong places, according to Sessions'' Web site
. Research has shown that toxic chemicals and radiation can only prevent frogs from developing limbs, Sessions said, but not induce them to grow additional limbs, as the parasite can and does. Experimenters in the laboratory have repeatedly witnessed frogs of different species growing extra limbs after they've added the parasite. "People get unduly concerned about this kind of abnormality because they always jump (no pun intended) to the conclusion that it is some kind of 'mutation,' " Sessions said, "and that it is caused by a nasty chemical pollutant or maybe radiation of some kind." When it comes to missing limbs -- as opposed to extra limbs -- the jury is still out. Research published recently found no parasites
in several Vermont lakes where deformed frogs have been found. "We believe that looking at the role of chemical pollution is the next logical step," said David Skelly, a Yale University researcher who published that study. "This is because we have found that tadpoles growing up next to agricultural fields are more likely to be deformed." He added, "We don't know what is causing them and some of the potential causes have implications for other vertebrates including humans."