The Silence of the Frogs

A team of scientists labors to figure out why so many frogs around the state are suddenly turning up deformed--and what

           Robert McKinnell peels back the white kitchen towel taped loosely over a fish tank containing nearly 40 small, dark-green frogs from Crow Wing county. They're swimming and hopping anxiously in about a half-inch of murky water. "The thing is," he says, "you often can't see their deformities until you pick them up." The University of Minnesota scientist seizes frogs one by one, flipping them around with his fingers to expose the particular defects of each one: missing limbs, extra limbs, webbed legs, extra toes. There was one that had only one eye--or so they thought until they opened its mouth and found the other partway down its throat.

           "Where's the five-legged frog?" McKinnell asks a worker in a white lab coat as he rummages around in another tank, tossing frogs back, one after another. "What the hell?" He finally comes up with the one he's been searching for. It's normal looking except for a short leg jutting out from its jaw. The frog squirms in McKinnell's hand. When one of its good legs inadvertently swings over the useless one, he looks up a little like a proud parent. "Look," he says, "he's holding hands with himself."

           McKinnell has been examining the habits and diseases of frog populations for almost 40 years now. His main interest is cancer; studying particular strains among frogs has led to some discoveries about human cancers. And he was one of the experts called in to take a look at genetic abnormalities in the children of the people who lived near Love Canal in the 1970s. His role in studying Minnesota's abnormal frogs is to search their DNA and internal organs for clues--parasites, mutations, or whatever else might turn up.

           He is currently part of a team of five scientists who are busy taking samples, examining pollutants, and conducting experimental matings in hope of finding out why so many frogs around the state are suddenly so badly deformed. The team, which received emergency funding from the Legislature via the state lottery and cigarette taxes, is trying to figure out not only what's happened to the frogs, but also what the situation might portend for human populations.

           Frogs are generally considered biogenetic canaries in the coal mine--indicators of ecological trouble to come. They encounter a wide array of environmental factors, spending their lives in a combination of aquatic and land environments and feeding on both plants and bugs; their eggs don't have shells and thus aren't protected from ultraviolet rays or pollutants. And owing to similarities in liver function, they also process certain chemicals the same way humans do. The shorthand explanation is that humans "have many of the same enzyme systems as frogs," according to McKinnell. "When humans encounter the same substances, they will be activated in humans as they are in frogs. If frogs are abnormal because of the conversion, that is a red flag to people who live in the area."

           "Funny frogs," as McKinnell calls them, first appeared en masse last fall in Le Sueur county near Henderson, about 50 miles southwest of the Twin Cities. A group of schoolkids from the Minnesota New Country School were on a field trip to study life around a pond on the property of a retired farmer. The site was once farmland, but it was transformed into a wildlife refuge years ago.

           Deformities have now surfaced at more than 20 confirmed sites in seven counties all over the state: Crow Wing, Le Sueur, Meeker, Pope, Scott, Sibley, and Stevens. There are many more unconfirmed sites, with new calls coming in every day. McKinnell feels overwhelmed. "Minnesota is the size of Great Britain. Can you expect two or three scientists to study all of Great Britain? No."

           Simply put, the team of scientists (two from the University of Minnesota, two from the Minnesota Pollution Control Agency, and one from South Dakota) is trying to find out whether the deformities are caused by a genetic alteration or chemical agent passed on by parents, or by a more immediate environmental contamination of eggs and tadpoles themselves. They have to act fast because abnormal frogs generally don't survive winters. MPCA aquatic biologist Judy Helgen, who heads the team, says there were some frogs with missing eyes and missing legs reported in 1993 after the massive flooding of the Minnesota River basin, but it was late in the year and scientists only found one specimen. When they went back the next year, the site was breeding normal frogs. There wasn't time to pinpoint a cause, says Helgen, but "what we are seeing now is different"--more widespread, and probably longer-lasting. "Here we may have a better chance to set up longer-term research," she says. "I don't think this can be understood in one summer. It may take three to five years to figure out."

           To get an idea of possible environmental factors, they're working to determine what all the sites have in common. Looking at a map, the counties in question make sort of a diagonal stripe from the upper-left corner of the state to the lower-right corner, with a few falling in unrelated areas such as the spot near Brainerd, in Crow Wing county. They lie in a variety of drainage bases, militating against toxins from a single river as the cause.
At first, the scientists were convinced that the deformities were related to some stirring up of old soil; all the ponds were either man-made or altered in some significant way. But then some ponds turned up that hadn't been excavated at all. McKinnell points out one theory, in an uncharacteristic fit of speculation, that all are near highways: "The highway department sprays and sprays herbicides along the highways. They apparently don't want to see anything blooming."

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