Tadpole tails and Roundup herbicide

April 2012

Tadpoles were used in a Roundup study
Photo by Olaf Tausch (Own work) [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-3.0 (http://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons

A study has been published which shows, for the first time, that Roundup herbicide stimulates adaptive physical responses during the development of a vertebrate animal.

Roundup is a very widely-used weed-killer. It is sprayed, in particular, on crops genetically transformed to survive it, and can end up in many non-target areas which are the homes of wildlife.

Adaptive physical responses produce important permanent changes during an animal's development which tailor the individual to the particular environment it's going to live in. Conversely, an inappropriate adaptive change can disadvantage the animal.

The study used tadpoles as a model vertebrate.


As the author explained:

“... 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.”

In the study, wetland ecosystems were created to which three species of tadpoles were added. The tadpoles were then exposed to three environmentally-relevant levels of Roundup and two common predators. When tadpoles find signs of predators in their surroundings, their tails grow larger to help them escape. In the experiment, two species of tadpoles responded to Roundup as they would to a predator. Roundup combined with predators caused the tadpoles' tail changes to be twice as large.

The presence of predators induces tadpole shape changes by altering their stress-hormones. That Roundup induced an effect so similar to that produced by the presence of a predator suggests the herbicide is a hormone disruptor. This could have relevance to many other animals, including humans.

Indeed, stress hormones in amphibians are not the only things disturbed by Roundup. A Brazilian team of scientists who investigated the progression of puberty in rats (a classic model for humans) concluded that “commercial formulation of glyphosate is a potent endocrine disruptor in vivo”.

OUR COMMENT

Adaptive responses include important physiological switches, such as aspects of the immune- and digestive-system function. If such switches are inappropriately re-set by environmental chemicals during early development, the outcome is likely to be debilitation and chronic disease.

SOURCES

• Rick A. Relyea, 2012, New effects of Roundup on amphibians: Predators reduce herbicide mortality; herbicides induce antipredator morphology, Ecological Applications 22
• B Rose Huber, New Study Is First to Show That Pesticides Can Induce Morphological Changes in vertebrate Animals, Says Pitt Researcher, http://www.news.pitt.edu/Pesticides_MOrph 30.03.12
• R. M. Romano, et al., 2010, Prepubertal exposure to commercial formulaiton of the herbicide glyphosate alters testosterone levels and testicular morphology. Archives of Toxicology 84
• Rick Relyea, Response to Monsanto's criticisms of his paper published in Ecological Applications 2005 which demonstrated highly lethal effects of the herbicide Roundup on amphibians, http://www.pitt.edu/~relyea/Site/Roundup.html