Acute toxicity and related metabolism of pyridalyl in Chironomus yoshimatsui and Hyalella azteca

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Acute toxicity and metabolism of a new insecticide pyridalyl were examined in the larval midge Chironomus yoshimatsui and adult amphipod Hyalella azteca using ¹⁴C-labeling. The median lethal concentrations (LC₅₀) of pyridalyl were determined to be 1.1 (48 hr) and 0.015 (96 hr) mg/l for midges and amphipods, respectively, based on its mean measured concentrations in water. Pyridalyl taken up by these organisms underwent ether cleavage at 3,3-dichloroallyloxy moiety followed by conjugation to a significantly higher extent in C. yoshimatsui. The similar acute median lethal body residues (LR₅₀) of pyridalyl estimated for both species from its body residues indicated an insignificant difference in its potential toxicity and therefore, uptake and metabolism behaviors were most likely to play a great role in the apparent toxicity.