3种酰胺类稻田除草剂对克氏原螯虾的急性毒性

目的] 研究稻虾共作模式条件下，稻田封闭除草剂对克氏原螯虾产生的急性毒性。方法] 采用半静态试验方法，研究3种酰胺类除草剂（乙草胺、丙草胺和丁草胺）对克氏原螯虾的急性毒性，计算3种酰胺类除草剂对克氏原螯虾的安全浓度，并分析其LC₅₀衰减规律。结果] 随着暴露时间和除草剂浓度的增加，虾体侧躺，步行足和游泳足活动频率降低，最终死亡。乙草胺对克氏原螯虾的96 h半致死浓度（LC₅₀）和安全浓度（SC）分别为0.0707和0.0146 mL·L^-1；丙草胺对克氏原螯虾的96 h LC₅₀和SC分别为0.0119和0.0021 mL·L^-1；丁草胺对克氏原螯虾的96h LC₅₀和SC分别为0.0073和0.0014 mL·L^-1。乙草胺、丙草胺及丁草胺除草剂LC₅₀随着暴露时间延长呈下降趋势，符合双曲线衰减模型，回归方程分别为：① y₁=2.0840x^-0.7380（R²=0.9973）；② y₂=0.1106x^-0.4930（R²=0.9872）；③ y₃=0.2236x^-0.7480（R²=0.9990）。克氏原螯虾对3种除草剂的敏感性由高到低依次为：丁草胺 > 丙草胺 > 乙草胺。结论] 乙草胺和丙草胺可在稻田综合种养生产过程中按常规剂量使用，而丁草胺按常规剂量使用可能存在较大的风险。

Acute toxicity of three amide herbicides to Procambarus clarkii

Aim] The widespread use of the herbicides in paddy fields may have some negative effects on Procambarus clarkii under the freshwater crayfisho-rice co-culture system.Method] Acute toxicity of three amides herbicides (etochlor, proxychlor and butochlor) on P. clarkii was studied using semi-static laboratory procedures to calculate the safe exposure concentrations (SC) and analyze the median lethal concentrations (LC₅₀) attenuation law.Result] The crayfish lay on its side, the motion frequency of pereiopods and pleopods decreased, and finally died with the increase of exposure time and drug concentration. The LC₅₀ (96 h) and SC of acetochlor, pretilachlor and butachlor in crayfish were 0.0707 and 0.0146 mL·L^-1, 0.0119 and 0.0021 mL·L^-1, and 0.0073 and 0.0014 mL·L^-1, respectively. The LC₅₀ declined with increased exposure time duration after 96 h of exposure, which basically meets hyperbola model. The regression equations were as follows:y₁=2.0840x^-0.7380 (R²=0.9973); y₂=0.1106x^-0.4930 (R²=0.9872); y₃=0.2236x^-0.7480 (R²=0.9990). The sensitivity of three herbicides in crayfish from highest to lowest was butachlor, pretilachlor and acetochlor.Conclusion] Under the conventional dose, acetochlor and pretilachlor could be used in the freshwater crayfisho-rice co-culture system, while butochlor might have a greater risk in conventional doses.