Research Finds Alligator Problems Also Evident In Less Polluted Lakes

February 09, 1998

GAINESVILLE --- Reproductive and hormonal problems documented in alligators living in a polluted Florida lake have turned up in alligators living in other Florida lakes thought to be more insulated from pollutants, say researchers at the University of Florida.

"These long-term studies are the answer to finding out how environments change over time, naturally and under man's hand. This should be a wake-up call. We have to make sure that similar problems are not occurring in ourselves," said UF Professor of Zoology Lou Guillette.

A research team led by Guillette made headlines in 1993 when they said pesticides could be responsible for sexual deformities and a previous population decline of alligators in Lake Apopka near Orlando.

That lake suffered from a severe pesticide spill in 1980 and commercial development on its shores.

"Everyone accepted the fact that Lake Apopka had a problem," Guillette said. "We now have the same problems on another lake."

Preliminary tests on Lake Okeechobee, Florida's biggest lake, showed the research team many of the same problems it had seen before: lower testosterone levels and small penis size in male alligators. In addition, tests also showed a new problem: altered thyroid hormone levels. The results are scheduled to appear in the Feb. 17 issue of the scientific journal Environmental Toxicology and Chemistry.

Also during the studies, researchers for the first time found possible effects of environmental toxicants on the thyroid, a critical regulator of growth in animals.

Biology Professor Drew Crain, a former student of Guillette now teaching at the University of Mississippi, said the study shows that problems found in Lake Apopka alligators are confined neither to that lake nor to one system in the animals.

"Previous studies have focused on the hormones associated with reproduction -- the steroid hormones testosterone and estradiol -- but now we have evidence of disruption in other endocrine-controlled systems," Crain said.

With funding from the Environmental Protection Agency and the National Institute of Environmental Health Services, the team wanted to see if the past findings from the Lake Apopka alligators were unique to that highly polluted lake.

"We were asking, "Are we getting the same effects with lower exposure, exposure that we would assume to be normal background?'" Guillette said.

Guillette said alligators are the perfect animals to study because they are predators at the top of the food chain, have a long life span and take several years to mature.

Researchers caught, measured, tagged and withdrew blood from 50 alligators each on Lake Okeechobee, Lake Apopka and Lake Woodruff, a relatively pristine lake located in a wildlife refuge. When the blood was tested and compared the results from the Lake Okeechobee alligators were very similar to the results they obtained from Lake Apopka.

"There was a 75- to 80-percent reduction in testosterone levels in males" when measured against the alligators in their control lake, he said. Hormonal irregularities found in Lake Okeechobee alligators were not as severe across-the-board as the Lake Apopka alligators, but a number of measures were troublesome, he said.

"The thing that now concerns us about Lake Okeechobee is we're no longer talking about a lake that has a Superfund site. We're no longer talking about a lake with a major pesticide spill. This is a huge body of water."

Guillette had help from Crain; Daniel Pickford, another former student of Guillette's; Franklin Percival of UF's Florida Cooperative Fish and Wildlife Research Unit; and Allan Woodward of the Florida Game and Freshwater Fish Commission.

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University of Florida

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