Globally, amphibian populations are declining with thirty-two percent of known species listed in the IUCN Red List categories of vulnerable, critically threatened, or endangered.  A variety of factors have been implicated in amphibian population declines, and pollutants are one of the most important. One group of pollutants, endocrine disrupting chemicals (EDCs), are globally distributed, transported atmospherically, and deposited in areas where amphibian populations have suffered massive declines. Relatively little is known, however, about the role that these chemicals play in the global decline of amphibians. It has become increasingly clear that many chemicals do not occur at concentrations that induce direct mortality, rather they have sub-lethal effects on immune, nervous, or reproductive systems that are manifested in adults, a life stage whose demise can have profound effect on amphibian populations.  Many agricultural chemicals are known to disrupt the endocrine systems of diverse taxa and have detrimental effects on the reproductive systems of exposed individuals.  However, many current-use pesticides are less well studied or their effects are highly controversial.  We compare gonadal development and morphology of 128 premetamorphic or metamorphic grey tree frogs (Hyla versicolor) in response to a single, ecologically relevant dose of six current-use pesticides (acetoclor, alachlor, metolachlor, atrazine, propazine, simazine), belonging to one of two chemical classes (Chloroacetanilide and Triazine). 

Results/Conclusions

The pesticides in this study influenced gonadal developmental rates, sex ratios, and gonadal morphology. Although we expected pesticides within classes to produce generalized patterns of effects, which would greatly facilitate our ability to understand and mitigate the effects of multiple chemicals in the environment, our results suggest that a more chemical specific approach may be necessary for identifying chemicals that alter reproductive development.  Understanding the differential reproductive effects of multiple commonly used pesticides provides an important step towards better understanding the mechanisms through which pesticides might be affecting wildlife and the role that these pesticides could play in the global decline of amphibian populations.