The widely-used herbicide Roundup has been discovered to induce physiological changes in animals, particularly amphibians according to Rick Relyea, Professor of Biological Sciences at the University of Pittsburgh and head of Pitt’s Pymatuning Laboratory of Ecology.

It has been found that “sublethal” and environmentally relevant concentrations of Roundup, the world’s most popular weed killer, caused two species of amphibians to alter their morphology. According to Relyea, this is the first study to show that a pesticide can induce morphological changes in a vertebrate animal.

Relyea emphasized that the tadpoles are not going through mutations, but rather changes that are naturally triggered by other catalysts, such as the speeding up of stress hormones.

Predators cause tadpoles to change shape by altering the stress hormones of tadpoles, causing physical changes such as larger tails to better escape the predators. Similar shape changes when exposed to Roundup suggest that the herbicide may interfere with the hormones of tadpoles and potentially many other animals.

Relyea said the intent of the study is not to go after Roundup or have it eliminated, but rather to recognize the outcomes of a very popular herbicide that the world did not know.

“We just saw the animals coming out of an experiment that just didn’t look right, so we measured them and found out they’re not right. The herbicide has caused them to be a very different looking animal than they should be. Those are the kind of things we want to figure out — why? Why is an herbicide causing an animal to apparently start using stress hormones, when as far as we know, an herbicide couldn’t do that,” Relyea said.