Pesticides Can Induce Morphological Changes in Vertebrate Animals

[Dead_Parrot]

PITTSBURGH— The world’s most popular weed killer, Roundup®, can cause amphibians to change shape, according to research published today in Ecological Applications.

Rick Relyea, 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, demonstrated that sublethal and environmentally relevant concentrations of Roundup® 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 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,” says Relyea. “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.

More: http://www.news.pitt.edu/Pesticides_MOrph
Paper (sub): http://www.esajournals.org/doi/abs/10.1890/11-0189.1

[mike_c]

1. here's the actual abstract, which is somewhat less sensational....

New effects of Roundup on amphibians: Predators reduce herbicide mortality; herbicides induce antipredator morphology

Rick A. Relyea
Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260 USA

The use of pesticides is important for growing crops and protecting human health by reducing the prevalence of targeted pest species. However, less attention is given to the potential unintended effects on nontarget species, including taxonomic groups that are of current conservation concern. One issue raised in recent years is the potential for pesticides to become more lethal in the presence of predatory cues, a phenomenon observed thus far only in the laboratory. A second issue is whether pesticides can induce unintended trait changes in nontarget species, particularly trait changes that might mimic adaptive responses to natural environmental stressors. Using outdoor mesocosms, I created simple wetland communities containing leaf litter, algae, zooplankton, and three species of tadpoles (wood frogs <Rana sylvatica or Lithobates sylvaticus>, leopard frogs <R. pipiens or L. pipiens>, and American toads <Bufo americanus or Anaxyrus americanus&gt . I exposed the communities to a factorial combination of environmentally relevant herbicide concentrations (0, 1, 2, or 3 mg acid equivalents [a.e.]/L of Roundup Original MAX) crossed with three predator-cue treatments (no predators, adult newts <Notophthalmus viridescens>, or larval dragonflies <Anax junius&gt . Without predator cues, mortality rates from Roundup were consistent with past studies. Combined with cues from the most risky predator (i.e., dragonflies), Roundup became less lethal (in direct contrast to past laboratory studies). This reduction in mortality was likely caused by the herbicide stratifying in the water column and predator cues scaring the tadpoles down to the benthos where herbicide concentrations were lower. Even more striking was the discovery that Roundup induced morphological changes in the tadpoles. In wood frog and leopard frog tadpoles, Roundup induced relatively deeper tails in the same direction and of the same magnitude as the adaptive changes induced by dragonfly cues. To my knowledge, this is the first study to show that a pesticide can induce morphological changes in a vertebrate. Moreover, the data suggest that the herbicide might be activating the tadpoles' developmental pathways used for antipredator responses. Collectively, these discoveries suggest that the world's most widely applied herbicide may have much further-reaching effects on nontarget species than previous considered.

So predator/pesticide interactions decreased pesticide lethality, and pesticide exposure alone induced developmental pathways normally induced by the presence of recognized predators. Of course, there are physiological costs of producing the deeper tails associated with the presence of predators, so tadpoles that do so MIGHT be at a disadvantage in mixed populations, although the significance is not at all clear yet.

I'm glad to see this work being done. It illuminates a side of environmental exposure that doesn't get nearly enough attention, and it provides data for making informed decisions about pesticide costs and benefits.

on edit-- sorry about the smilies-- they're the result of unintentional interaction between the author's text and DU's HTML code.