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Are potential behavioral effects caused by pesticide exposure contributing to the decline of terrestrial amphibians?
Hirsch, Regina1,2, Temple, Stanley1, 1 2
ABSTRACT- In Wisconsin, many species of anurans migrate to their breeding ponds during early spring, frequently migrating through agricultural fields. This is the exact time corn insecticides, which amphibians may absorb through their skin, are applied to the soil. Amphibians may not absorb enough to cause immediate death. However, insecticides may change their behavior, thus resulting in death. We developed a methodology to determine exposure of terrestrial amphibians to insecticides by determining the LC50, NOEC and assessing neuro-behavioral effects (ability to avoid predation, avoid dessication, or find and capture prey). The validity of our methodology was tested on adult northern leopard frogs (Rana pipiens) exposed to five concentrations of the insecticide, Tefluthrin, (0.078, 0.13, 0.22, 0.36, and 0.60 mg/L) and control. Frogs were placed in shallow aqueous solutions of either a treatment concentration or distilled water for 24-hours, with a 7-day post-exposure observation period. The degree of neuro-behavioral effects were determined by a series of behavioral tests. Results indicated a significant behavioral dose-response to the five concentrations; higher treatment concentrations produced more severe and detectable behavioral responses. The LC50 and NOEC were calculated to be 0.50 mg/L and 0.078 mg/L, respectively. The use of neuro-behavioral testing is useful for determining acute toxicity for pesticides. In addition, it can be used on a variety of terrestrial amphibian species and age classes (from newly metamorphosed amphibians to breeding adults).
KEY WORDS: amphibians, neuro-behavior, pesticides, toxicity