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(212) Timing of Exposure Versus Cumulative Exposures: Effects of an Insecticide on Green Frogs (Rana clamitans).
Boone, Michelle*,1, Bridges, Christine1, 1 USGS Columbia Environmental Research Center, Columbia, MO, USA
ABSTRACT- Exposure to a pesticide multiple times may be particularly relevant for the short-lived pesticides that are prevalent today, which may lead to repeated exposures to amphibian populations imbedded in or near agricultural areas. The objective of our study was to determine how cumulative exposure versus single exposure at different times during development affected green frog (Rana clamitans) survival to metamorphosis, tadpole survival, tadpole mass, and tadpole developmental stage reared in low- and high-density outdoor cattle tank ponds. Tadpoles were exposed to carbaryl 0, 1, 2, or 3 times at 14 day intervals; single doses occurred at one of three times, early, mid, or later in development. We found that cumulative exposures had a greater impact than single exposures during development. Ponds exposed to multiple levels of carbaryl had increased rates of metamorphosis compared to controls, indicating that presence of carbaryl can stimulate metamorphosis. Presence of carbaryl resulted in more developed tadpoles in most ponds exposed to carbaryl when compared to controls. Our study illustrates the importance of including realistic application procedures when evaluating the effects of a pesticide.
Key words: amphibian, insecticide, carbaryl, multiple exposures
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