Abstract: Quinclorac shows acute toxicity to Carassius auratus.Under the concentration of 1/2,1/4,1/6 and 1/8 LC ₅₀ of quinclorac,its effects on gill and liver Na⁺-K⁺ -ATPase, and Mg²⁺ -ATPase activities were studied.Results indicated that:(1)At the water temperature of 23±1 ℃,the LC ₅₀ value of 25% EC quinclorac to Carassius auratus at the 24th, 48th,72th and 96th hour was 151.64,150.92,149.60 and 149.14 mg·L ^-1 ,respectively,so it is a kind of low toxicity pesticide.(2)The inhibition of Na⁺-K⁺ -ATPase and Mg²⁺ -ATPase in gill and liver increased with the concentration of quinclorac,showing a striking dose response relationship,which can,therefore,be used as a good biomarker for quinclorac pollution.Mechanisms of the inhibition of Na⁺-K⁺ -ATPase、Mg²⁺ -ATPase by quinclorac were also discussed.

Key words: quinclorac, Carassius auratus, toxicity, LC ₅₀, ATPase