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® (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 μg 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 μg 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. © 2007 Wiley Periodicals, Inc. Environ Toxicol 22: 194–202, 2007.