Ej. Materna et al., EFFECTS OF THE SYNTHETIC PYRETHROID INSECTICIDE, ESFENVALERATE, ON LARVAL LEOPARD FROGS (RANA SPP), Environmental toxicology and chemistry, 14(4), 1995, pp. 613-622
Leopard frog (Rana spp.) tadpoles exposed to esfenvalerate in the labo
ratory experienced a decrease in activity at concentrations as low as
1.3 mu g/L and exhibited a convulsive, twitching response at concentra
tions of 3.6 mu g/L. The 96-h median lethal concentration was 7.29 mu
g/L. Temperature influenced amphibian mortality; the mortality concent
ration-response slope at 22 degrees C was significantly greater than a
t 18 degrees C. Tadpoles exposed in a pond showed the same responses (
inactivity, convulsive actions, and death) at similar concentrations a
s laboratory test organisms. Surviving tadpoles from laboratory tests
resumed normal behavior 1 week after being placed into clean water, bu
t most of those tadpoles that exhibited convulsive behavior during ini
tial exposure eventually died. Tadpoles surviving pond exposures showe
d no later mortality, but rather exhibited a negative density-growth r
elation. Measured pyrethroid concentrations in ponds and streams adjac
ent to sprayed fields do not exceed levels associated with convulsive
twitching or mortality in larval amphibians; however, they do exceed c
oncentrations associated with inactivity and fish and invertebrate mor
tality, which may indirectly affect larval amphibians.