No abstract

Leopard frog (Rana spp.) tadpoles exposed to esfenvalerate in the laboratory experienced a decrease in activity at concentrations as low as 1.3 pg/L and exhibited a convulsive, twitching response at concentrations of 3.6 pg/L. The 96-h median lethal concentration was 7.29 pg/L. Temperature influenced amphibian mortality; the mortality concentration-response slope at 22°C was significantly greater than at 18°C. Tadpoles exposed in a pond showed the same responses (inactivity, convulsive actions, and death) at similar concentrations as laboratory test organisms. Surviving tadpoles from laboratory tests resumed normal behavior 1 week after being placed into clean water, but most of those tadpoles that exhibited convulsive behavior during initial exposure eventually died. Tadpoles surviving pond exposures showed no later mortality, but rather exhibited a negative density-growth relation. Measured pyrethroid concentrations in ponds and streams adjacent to sprayed fields do not exceed levels associated with convulsive twitching or mortality in larval amphibians; however, they do exceed concentrations associated with inactivity and fish and invertebrate mortality, which may indirectly affect larval amphibians.

Leopard frog (Rana spp.) tadpoles exposed to esfenvalerate in the laboratory experienced a decrease in activity at concentrations as low as 1.3 μg/L and exhibited a convulsive, twitching response at concentrations of 3.6 μg/L. The 96‐h median lethal concentration was 7.29 μg/L. Temperature influenced amphibian mortality; the mortality concentration‐response slope at 22°C was significantly greater than at 18°C. Tadpoles exposed in a pond showed the same responses (inactivity, convulsive actions, and death) at similar concentrations as laboratory test organisms. Surviving tadpoles from laboratory tests resumed normal behavior 1 week after being placed into clean water, but most of those tadpoles that exhibited convulsive behavior during initial exposure eventually died. Tadpoles surviving pond exposures showed no later mortality, but rather exhibited a negative density‐growth relation. Measured pyrethroid concentrations in ponds and streams adjacent to sprayed fields do not exceed levels associated with convulsive twitching or mortality in larval amphibians; however, they do exceed concentrations associated with inactivity and fish and invertebrate mortality, which may indirectly affect larval amphibians.