Short-term effects of Quirlan (chlorfenvinphos) on the behavior and acetylcholinesterase activity of Gambusia holbrooki.

Chlorfenvinphos is a widespread organophosphorous (OP) insecticide and it is a reported hazardous chemical for aquatic nontarget organisms. This study intended to evaluate the effects of sublethal concentrations of Quirlan(R) (commercial formulation of chlorfenvinphos) on several behavioral parameters of the mosquitofish, Gambusia holbrooki. The insecticide showed high toxicity to G. holbrooki by significantly impairing all the behavioral responses (location in the test vessel, activity/excitability, swimming, and feeding), exhibiting a time-dependent pattern. Behavioral EC50s, after a 96-h exposure, ranged from 5.2 to 9.0 microg L(-1). As OP pesticides are acutely neurotoxic, acetylcholinesterase (AChE) activity was also selected for use as a biomarker in this study for the establishment of a relationship with the observed behavior abnormalities. A strong inhibition of AChE was observed in fish exposed to chlorfenvinphos (IC50 = 3.55 microg L(-1)). Behavioral impairment was registered in fish with >40% AChE inhibition levels, while mortality was only observable in fish exhibiting AChE inhibition levels >80%. Additionally, significant correlations were found between behavioral impairment and AChE inhibition, suggesting a mechanistic link. These results show the usefulness of integrating biochemical and individual endpoints in a small-sized model species, and confirm a potential hazard of chlorfenvinphos to nontarget aquatic organisms.