Effects of a Neonicotinoid Insecticide on Larval Stages of the Green Frog, Rana clamitans
Bayci, Melissa N.
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Agricultural use of insecticides to increase crop yield is potentially detrimental to the ecosystem due to potential harmful effects to non-target species living in the same area. Neonicotinoids are a new class of insecticide that appear less detrimental because of their increased rate of degradation and ability to bind more readily to the insect acetylcholine neurotransmitter, rather than that of vertebrates. Their effects on non-target species such as amphibians, however, are not well understood. In environmental studies, frogs are commonly used as an indicator taxon of ecosystem conditions because of their sensitivity to pollutants, ability to absorb chemicals through their skin, and ease of rearing in laboratory settings. We measured effects of a neonicotinioid insecticide, imidacloprid, on the green frog Rana clamitans by subjecting tadpoles of this species to different concentrations of imidacloprid. We examined effects on growth, development, survivorship and behavior of the tadpoles. The insecticide did not have measurable effects on tadpole growth or development. On the other hand, the insecticide had a measurable effect on both survivorship and behavior of green frog tadpoles at the two highest concentrations, 200 mg/L and 400 mg/L of insecticide. Observed effects could be a consequence of overstimulation of nerves, which can result in paralysis and/or death of an organism. Because this study was conducted in a laboratory setting following the acute toxicity testing protocol, it is unlikely tadpoles would be exposed to such concentrations in a natural setting. Therefore, although imidacloprid had detrimental effects on survivorship and behavior in our study, it is likely a safer alternative than other classes of insecticides if used as directed.