农药胁迫下溞类生物量与水体中NAGase活性的关系

Daphnid Biomass and Activity of Free-living NAGase Under Pesticide Stresses

为探索游离态N-乙酰-β-D-氨基葡萄糖苷酶(简称NAGase,又称壳二糖酶)作为农药对水生节肢动物胁迫效应指示因子的可行性,将大型溞、多刺裸腹溞、老年低额溞作为受试生物,虱螨脲、丁醚脲、乙螨唑作为受试药剂,研究了游离于水中的NAGase的活性与溞类生物量之间的对应关系。以全部63个被暴露群体的生物量为自变量(x),以相应群体释放到水中的NAGase的活性为应变量(y),得到回归方程y=0.000 603x+0.004 33,该方程的r值和P值分别为0.687和0.00。两者之间的对应关系证明了利用水中NAGase活性来预测被暴露群体生物量的可行性。进一步的研究显示,作为胁迫因子,乙螨唑在高浓度(1.6μg·L-1)下促使溞类群体萎缩,NAGase活性下降则相对滞后。涉及10种农药的离体试验表明,农药直接影响NAGase活性的最低浓度远高于其在野外水体中可能存在的最高浓度,说明农药实际上不可能通过直接影响酶活性(无论是诱导,还是抑制)来干扰被暴露群体的生物量预测。

Free β-N-acetyl-D-glucosaminidase（NAGase,or chitobiase）may be an indicator of aquatic arthropod with respect to pesticide stresses.In this experiment,three species of Daphnids,i.e.Daphnia magna Straus,Moina macrocopa,and Simocephalus vetulus and three presticides,lufenuron,diafenthiuron,and etoxazole,were used to study the arthropod biomass and free-living NAGase activity.It was found that arthropod biomass（x）and NAGase activity（y）had significant correlation（y=0.000 603x＋0.004 33,r=0.687 and P=0.00）,suggesting the feasibility of using free-living NAGase activity to predict the biomass of the exposed arthropod populations.In viro studies with 10 pesticides,i.e.lufenuron,diafenthiuron,and etoxazole,butachlor,trazodone,chlorpyrifos,fenvalerate,imidacloprid,pymetrozine,and chlorantraniliprole,showed that their minimal concentrations at which the activity of free-living NAGase was directly affected were much higher than the highest concentrations found in water bodies.These results suggest that the biomass could be predicted without underestimation by NAGase activity.