Pesticide exposure and its effects on stress hormone levels in amphibians
Amphibian populations are in decline around the globe due to a variety of factors ranging from habitat destruction to pesticide use. One of the most widely used pesticide active ingredients throughout the world is atrazine (ATZ). The purpose of our study was to compare accumulation or body burden and stress response in frogs after exposure to ATZ and one of its formulated products, St. Augustine, which also contains many inactive ingredients. Southern leopard frogs (Lithobates sphenocephala) were exposed to ATZ or St. Augustine for a period of eight hours. Exposures were done on sandy-loam soil and frogs were dehydrated the night before to facilitate uptake. A subset of frogs was then assessed for pesticide body burden using an extraction protocol and analysis on the GC-MS. The remaining frogs were evaluated for levels of corticosterone (CORT), a hormone released in response to stress, by using a non-lethal method for hormone collection.
Preliminary results show that although body burdens were not significantly different between the ATZ and St. Augustine groups, CORT levels were higher among control frogs than either of the pesticide treated groups. There was no significant difference in CORT levels between frogs exposed to either ATZ or St. Augustine. Our results indicate that pesticide exposure in amphibians may suppress the release of stress hormones. Although the long-term effects of pesticide exposure are not known, short-term effects such as stress may alter reproductive output and survival among amphibians.