Tuesday, April 3, 2012
Popular weedkiller causes deformities in amphibians
By Bob Berwyn
Summit County Citizens Voice, USA
April 3, 2012
SUMMIT COUNTY - Exposure to sub-lethal doses of a widely used weed killer caused tadpoles to grow abnormally large tails, according to University of Pittsburgh biologist Rick Relyea, who has been studying ecotoxicology and ecology for two decades.
Relyea has conducted extensive research on the toxicity of Roundup® to amphibians. Monsanto has challenged some of the studies and Relyea has responded to the criticism.
In his latest study, Relyea set up large outdoor water tanks that contained many of the components of natural wetlands. Some tanks contained caged predators, which emit chemicals that naturally induce changes in tadpole morphology (such as larger tails to better escape predators).
After adding tadpoles to each tank, he exposed them to a range of Roundup® concentrations. After 3 weeks, the tadpoles were removed from the tanks. “It was not surprising to see that the smell of predators in the water induced larger tadpole tails,” Relyea said. “That is a normal, adaptive response. What shocked us was that the Roundup® induced the same changes.
Moreover, the combination of predators and Roundup® caused the tail changes to be twice as large.”
Because tadpoles alter their body shape to match their environment, having a body shape that does not fit the environment can put the animals at a distinct disadvantage.
According to Relyea, this is the first study to show that a pesticide can induce morphological changes in a vertebrate animal.
Predators cause tadpoles to change shape by altering the stress hormones of tadpoles, says Relyea. The similar shape changes when exposed to Roundup® suggest that Roundup® may interfere with the hormones of tadpoles and potentially many other animals.
“This discovery highlights the fact that pesticides, which are important for crop production and human health, can have unintended consequences for species that are not the pesticide’s target,” Relyea said. ” Herbicides are not designed to affect animals, but we are learning that they can have a wide range of surprising effects by altering how hormones work in the bodies of animals. This is important because amphibians not only serve as a barometer of the ecosystem’s health, but also as an indicator of potential dangers to other species in the food chain, including humans.”
The research was published today in Ecological Applications. Relyea is a University of Pittsburgh professor of biological sciences in the Kenneth P. Dietrich School of Arts and Sciences and director of Pitt’s Pymatuning Laboratory of Ecology.