| dc.description.abstract | Neonicotinoid insecticides were designed to be selective for insect nicotinic acetylcholine
receptors (nAChRs), however recent studies indicate they may cause subtle toxicity in
fish. Imidacloprid (IM) and thiamethoxam (TM) are neonicotinoids found together in
Wisconsin surface waters, yet no studies have evaluated their combined toxicities to fish.
The aim of this study was to better understand the potential for IM and IM:TM mixtures
to activate the nAChR and to affect the development (hatching, length, survival) or
behavior (embryonic motor activity, predator escape response) of fathead minnows
(Pimephales promelas). Embryos and larvae were exposed to IM or to mixtures of
IM:TM. Only survival was significantly affected. Chronic exposure to 0.2 μg IM/L and
1:1 0.02 and 200 μg IM/L:μg TM/L resulted in reduced survival. Survival improved in
those exposed to mixtures (1:1 2, 20 μg IM/L:μg TM/L, 1:4 0.05 μg IM/L: 0.20 μg
TM/L, and 1:5 0.05 μg IM/L: 0.25 μg TM/L); however, high mortality was observed in
controls. The effect on survival, but not behavior implies that IM and TM may have low
affinities for the vertebrate nAChR and interact with a different system in the fish, which
was supported by molecular modeling. | en_US |
