Acute Toxicity of Two Organophosphorus Pesticides to Juveniles Cirrhina mrigola

Acute toxicity of fipronil, dimethoate on the Cirrhina mrigola juveniles without feeding were studied in the standing water at 28.1±0.6 ℃. The weight and length of the juvenile were (5.56±0.31)cm and (2.67±0.40)g respectively. The result showed that the orders of the toxicity of these two pesticides on juve- niles Cirrhina mrigola was fipronil dimethoate. We found that the median-lethal concentrations(LC50)in 24 h, 48 h, 72 h, 96 h to juveniles Cirrhina mrigola were 0.020 mg/L(confidence interval (CI0.95): [0.009, 0.066]), 0.017 mg/L(CI0.95: [0.007, 0.064]), 0.010 mg/L(CI0.95: [0.004, 0.041]), 0.004 mg/L(CI0.95: [0.002, 0.017]) forfipronil respectively; 315.500 mg/L (CI0.95: [150.453, 372.135]), 142.233 mg/L (CI0.95: [64.565, 190.985]), 62.517 mg/L(CI0.95: [25.136, 102.825])and 28.708 mg/L(CI0.95: [12.759, 46.174])for dimethoate, respectively. And the safe mass -concertrations of fipronil, dimethoate to juveniles Cirrhina mrigola were 0.000 4 mg/L, 2.870 8 mg/L respectively. Finally, the thesis discussed the characters of acute toxicity, the effects and the safe-concentration of these pesticides to juveniles Cirrhinus mrigala.