Pyrethroids are among the most widely applied insecticides worldwide and cypermethrin is the pyrethroid most used in Argentina. Pesticides used in crops can reach adjacent watercourses through runoff and may lead to non-target fauna receiving toxic pulse exposures. The aim of this study was to determine the effects of cypermethrin pulse exposures on the widely distributed crustacean Simocephalus vetulus. The 48h-LC50 of cypermethrin for S. vetulus was determined at 0.18 ± 0.09 μg/L. To assess the effects of cypermethrin under environmentally realistic exposures, two experiments were performed. In the first one, specimens were exposed for 90 min to cypermethrin at 0.02 (T1), 0.2 (T2) and 1 μg/L (T3), transferred to clean water and monitored for 24 h as regards survival and feeding rates; specimens exposed to T2 and T3 concentrations showed significant lower feeding rates than those in the control group. In the second experiment, specimens were exposed for 90 min every 7 days and monitored over 25 days; S. vetulus showed lower cumulative fecundity and reproduction rates at all concentrations tested, and lower population growth at the highest concentration. All exposure concentrations lay within reported environmental concentrations and risk assessment indicated risk (RQ > 1), suggesting that sensitive species would be affected by such pulse exposures of cypermethrin. The present study thus suggests that ongoing agricultural practices affect the non-target invertebrates in streams adjacent to crops.

拟除虫菊酯是全世界使用最广泛的杀虫剂，而氯氰菊酯是阿根廷最常用的拟除虫菊酯。农作物中使用的农药可通过径流到达邻近的河道，并可能导致非目标动物受到毒性脉冲暴露。本研究的目的是确定氯氰菊酯脉冲暴露对广泛分布的甲壳纲Simocephalus vetulus的影响。氯氰菊酯对维氏链球菌48h-LC50的影响测定值为0.18±0.09μg/ L。为了评估氯氰菊酯在环境实际暴露下的作用，进行了两个实验。在第一个样品中，将标本分别以0.02（T1），0.2（T2）和1μg/ L（T3）的氯氰菊酯暴露90分钟，转移到纯净水中并监测24小时的存活率和摄食率；暴露于T2和T3浓度的标本显示进食速率明显低于对照组。在第二个实验中，每7天将标本暴露90分钟，并在25天内进行监测；维氏葡萄球菌在所有测试浓度下均显示出较低的累积繁殖力和繁殖率，而在最高浓度下则显示较低的种群生长。所有暴露浓度均在报告的环境浓度之内，并且风险评估表明存在风险（RQ> 1），这表明敏感物种将受到此类氯氰菊酯的脉冲暴露影响。因此，本研究表明，正在进行的农业实践影响着邻近作物的河流中的非目标无脊椎动物。