Alligators have a lot more in common with humans than you might think, and the ways their bodily systems develop – or deform — before hatching are a lot like the ways human babies grow in their mothers’ uteruses.
|Dr. Louis J. Guillette Jr.|
And tiny, tiny doses of chemicals that can cause alligators to die before they hatch or to hatch with significant birth defects can have similar impacts on humans.
That was the message that Louis J. Guillette Jr., a reproductive biologist, delivered to about 150 people who attended his lecture Sept. 14 at the University of Minnesota. The lecture was sponsored by the Freshwater Society and the university’s College of Biological Sciences.
To view a videotape of Guillette’s lecture, click here. To hear a Minnesota Public Radio interview with Guillette and University of Minnesota Professor Deborah Swackhamer, click here. To read a Freshwater interview with Guillette, click here. And to view a KARE-11 television interview with Guillette, click here.
Guillette is a professor of obstetrics and gynecology at the Medical University of South Carolina. He also
has an endowed professorship at the Hollings Marine Laboratory in Charleston, S.C. Until recently, he was a professor at the University of Florida, where he spent 25 years studying wildlife – mostly alligators – living in polluted waters.
Ask most people what determines human health, and if they think a bit they are likely to say germs and genes, Guillette said. But the
Louis J. Guillette Jr., left, Heiko Schoenfuss, Deborah
environment is as big, sometimes bigger, factor than either germs or genes, he said.
He said research he and others have conducted on alligators has now established that even small amounts of many chemicals in the environment often cause significant birth defects and can cause fertilized alligator eggs to fail to hatch or to develop into males instead of females, or females instead of males.
Guillette said his research on alligators began as an effort to determine why, at some lakes, only about half the alligator eggs were hatching successfully, while 90 percent were hatching at other lakes.
Initially, he said, researchers thought the problem was something in the alligators’ diet or in their nesting experiences. Eventually, he said, the researchers hypothesized that chemicals from agricultural pesticides, storm water runoff and sewage were causing the alligators’ problems.
Then research in the laboratory on eggs and fetuses confirmed that the chemicals were, indeed, causing birth defects involving the reproductive organs of both males and female alligators. In many cases, he said the chemicals affected the ways genes caused cells to develop.
And the researchers recognized that the pathologies they were seeing in the alligators were similar, in some ways, to the birth defects that thousands of women experienced after their mothers were treated with diethylstilbestrol, a synthetic estrogen, during their pregnancies in the 1950s.
Scientists can not ethically experiment on humans, the way they can on alligators, or mice or other animals, so link between exposure to environmental pollutants and human birth defects probably can never be definitively proven. But Guillette said he believes that the basic elements of human and animal bodily systems are enough alike that many of the conclusions about alligators’ responses to the chemicals in their environment can also be made for humans.
A panel of three Minnesota water experts – Swackhamer; Heiko Schoenfuss, a St. Cloud State University Professor; and John Linc Stine, assistant commissioner of the Minnesota Department of Health – joined Guillette in responding to questions from the audience.