农药是用于控制的物质,预防,和驱除农业中的害虫。其中,新烟碱类由于其有效地针对害虫,已成为增长最快的杀虫剂类别。它们通过与昆虫中枢神经系统中的烟碱乙酰胆碱受体(nAChRs)强烈结合而起作用,导致受体阻塞,瘫痪和死亡。尽管它们对昆虫有选择性,这些物质可能对非目标生物有害,包括蚯蚓.尽管蚯蚓在北美等一些地区可能具有侵袭性,它们有助于土壤结构的发展,水管理,营养循环,污染修复,文化服务,积极影响环境,特别是在土壤生态系统中。因此,这项研究旨在开发一种新型的earth行为测定法,因为行为是毒性测定的敏感标记,并证明了其在评估各种新烟碱类的毒性中的应用。这里,我们将fetidaEisenia暴露于1和10ppb的八种新烟碱(啶虫脒,clothianidin,dinotfuran,吡虫啉,尼坦吡喃,噻虫啉,噻嗪,和sulfxaflor)3天,以观察其行为毒性。总的来说,所有的新烟碱都会降低他们的运动能力,表现为平均速度降低24.94-68.63%,冻结时间移动比增加1.51-4.25倍,改变了它们的运动方向和复杂性,用分形维数值下降24-70%来表示。此外,一些新烟碱,是啶虫脒,dinotfuran,吡虫啉,尼坦吡喃,和磺胺草剂,甚至可以改变他们的探索行为,这可以通过在中心区域值花费的时间增加6.94-12.99倍来显示。此外,基于PCA和热图聚类结果,噻虫嗪被发现是新烟碱,在测试的农药中具有最不明显的行为毒性作用,因为两种浓度的这些新烟碱处理组与对照组归为同一主要簇。最后,还进行了分子对接,以检查新烟碱与乙酰胆碱结合蛋白(AChBP)的可能结合机制,负责神经传递。分子对接结果证实,每种新烟碱都与AChBP具有相对较高的结合能,硫胺素具有最低的结合能,这与其相对较低的行为毒性一致。因此,这些分子对接结果可能暗示了观察到的行为改变背后的可能机制。总而言之,本研究表明,所有的新烟碱都改变了蚯蚓的行为,这可能是由于它们与一些特定的神经递质结合的能力,目前的发现提供了新烟碱对环境的毒性的见解,尤其是土壤生态系统中的动物.
Pesticides are substances used for controlling, preventing, and repelling pests in agriculture. Among them, neonicotinoids have become the fastest-growing class of insecticides because of their efficiency in targeting pests. They work by strongly binding to nicotinic acetylcholine receptors (nAChRs) in the central nervous system of insects, leading to receptor blockage, paralysis, and death. Despite their selectivity for insects, these substances may be hazardous to non-target creatures, including earthworms. Although earthworms may be invasive in some regions like north America, they contribute to the development of soil structure, water management, nutrient cycling, pollution remediation, and cultural services, positively impacting the environment, particularly in the soil ecosystem. Thus, this study aimed to develop a novel earthworm behavior assay since behavior is a sensitive marker for toxicity assay, and demonstrated its application in evaluating the toxicity of various neonicotinoids. Here, we exposed Eisenia fetida to 1 and 10 ppb of eight neonicotinoids (acetamiprid, clothianidin, dinotefuran, imidacloprid, nitenpyram pestanal, thiacloprid, thiametoxam, and sulfoxaflor) for 3 days to observe their behavior toxicities. Overall, all of the neonicotinoids decreased their locomotion, showed by a reduction of average speed by 24.94-68.63% and increment in freezing time movement ratio by 1.51-4.25 times, and altered their movement orientation and complexity, indicated by the decrement in the fractal dimension value by 24-70%. Moreover, some of the neonicotinoids, which were acetamiprid, dinotefuran, imidacloprid, nitenpyram, and sulfoxaflor, could even alter their exploratory behaviors, which was shown by the increment in the time spent in the center area value by 6.94-12.99 times. Furthermore, based on the PCA and heatmap clustering results, thiametoxam was found as the
neonicotinoid that possessed the least pronounced behavior toxicity effects among the tested pesticides since these
neonicotinoid-treated groups in both concentrations were grouped in the same major cluster with the control group. Finally, molecular docking was also conducted to examine neonicotinoids\' possible binding mechanism to Acetylcholine Binding Protein (AChBP), which is responsible for neurotransmission. The molecular docking result confirmed that each of the neonicotinoids has a relatively high binding energy with AChBP, with the lowest binding energy was possessed by thiametoxam, which consistent with its relatively low behavior toxicities. Thus, these molecular docking results might hint at the possible mechanism behind the observed behavior alterations. To sum up, the present study demonstrated that all of the neonicotinoids altered the earthworm behaviors which might be due to their ability to bind with some specific neurotransmitters and the current findings give insights into the toxicities of neonicotinoids to the environment, especially animals in a soil ecosystem.