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

Abstract

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.