Influence of Cyhalofop-butyl on growth and tissue accumulation of juvenile Chinese mitten crab

Effect of Cyhalofop-butyl on the crab growth was preliminarily determined by acute (96 h) and chronic (40 d) experiments. During this process, the accumulation of Cyhalofop-butyl in juvenile Chinese mitten crab was detected by HPLC, the change of Cyhalofop-butyl concentration in the water at 12 hours intervals up to 96 hours was observed and the degradation rate of Cyhalofop-butyl was calculated. The results showed that during acute experiment, the concentrations of Cyhalofop-butyl were 11 g/mL, 5.5g/mL and 2.8g/mL, respectively, the death rate of juvenile Chinese mitten crab obviously increased with Cyhalofop -butyl concentration increasing, death rate was significantly higher in 11 滋g/mL Cyhalofop -butyl treatment (33.33%) than in both 5.5g/mL and 2.8g/mL group. In the chronic experiment, the concentrations of Cyhalofop-butyl were 1.1g/mL, 0.5g/mL and 0.2g/mL, no significant difference in weight, death rate and average days of molt wasdetected. Both in the acute and chronic experiments, the Cyhalofop-butyl concentration in hepatopancreas was the highest, followed by gill and muscle. The highest Cyhalofop-butyl concentration (in the highest concentration treatment group) in hepatopancreas was 8.61 滋g/mL. The degradation speed of Cyhalofop-butyl with the concentration of 11g/mL, 5.5 滋g/mL and 2.8 滋g/mL was respectively 83.91%, 68.73% and 53.09%. The degradation rates of Cyhalofop-butyl significantly increased with the increase of time in 48 h, especially obvious in 24 h. In conclusion, the results showed that the massive death of crabs weren't observed in Cyhalofop-butyl treatment. No obvious influence on molt and growth of Chinese mitten crab by Cyhalofop -butyl treatment was found. Meanwhile, the accumulation of Cyhalofop-butyl in juvenile crab was limited.