UK Centre for Ecology & Hydrology, Maclean Building, Crowmarsh Gifford, Wallingford, Oxfordshire, OX10 8BB, UK.
Cardiff School of Biosciences, BIOSI 1, University of Cardiff, P.O. Box 915, Cardiff, CF10 3TL, UK.
Environ Pollut. 2021 Mar 1;272:115914. doi: 10.1016/j.envpol.2020.115914. Epub 2020 Nov 3.
The scale of variation in species sensitivity to toxicants has been theoretically linked to mode of action. Specifically, it has been proposed there will be greater variations for chemicals with a putative specific biological target than for toxicants with a non-specific narcotic mechanism. Here we test the hypothesis that mode of action is related to variation in sensitivity in a specifically designed experiment for species from a single ecologically important terrestrial taxa, namely earthworms. Earthworm toxicity tests were conducted with five species for four chemicals, providing a series of increasingly complex modes of action: a putative narcotic polycyclic aromatic hydrocarbon (fluoranthene), and three insecticides (chlorpyrifos, cypermethrin, imidacloprid) with known neuronal receptor targets. Across all the chemicals, the standard epigeic test species Eisenia fetida and Lumbricus rubellus, were generally among the two least sensitive, while the endogenic Aporrectodea caliginosa and Megascolecidae Amynthas gracilis were generally more sensitive (never being among the two least sensitive species). This indicates a potential for bias in the earthworm ecotoxicology literature, which is dominated by studies in epigeic Lumbricidae, but contains few endogeic or Megascolecidae data. Results confirmed the lowest range of variation in sensitivities for effects on reproduction was for fluoranthene (2.5 fold). All insecticides showed greater variation for species sensitivity (cypermethrin: 7.5 fold, chlorpyrifos: 10.3 fold, imidacloprid: 31.5 fold) consistent with the specific mechanisms of the pesticides. Difference in toxicodynamics, based on mode of action specificity and receptor complexity was reflected in the magnitude of sensitivity variation. However, measurements of tissue concentrations also indicated the potential importance of toxicokinetics in explaining species sensitivity variations for chlorpyrifos and cypermethrin.
物种对毒物敏感性的变化幅度在理论上与作用模式有关。具体来说，有人提出，对于具有假定特定生物靶标的化学物质，其变化幅度将大于具有非特异性麻醉作用机制的毒物。在这里，我们通过专门设计的实验来检验作用模式与敏感性变化之间存在关联的假设，该实验针对的是来自单一生态重要陆地分类群的单一物种，即蚯蚓。我们对 5 种物种进行了 4 种化学物质的毒性测试，提供了一系列越来越复杂的作用模式：一种假定的麻醉多环芳烃（荧蒽），以及 3 种具有已知神经元受体靶标的杀虫剂（毒死蜱、氯菊酯、吡虫啉）。在所有这些化学物质中，标准表生测试物种赤子爱胜蚓和环毛蚓通常是最不敏感的两种，而内生的巨蚓属和颤蚓科通常更敏感（从未是最不敏感的两种物种之一）。这表明蚯蚓生态毒理学文献中可能存在偏见，该文献主要以表生的巨蚓科研究为主，但内生或颤蚓科的数据很少。结果证实，对繁殖产生影响的氟蒽的敏感性变化范围最小（2.5 倍）。所有杀虫剂对物种敏感性的变化幅度都更大（氯菊酯：7.5 倍，毒死蜱：10.3 倍，吡虫啉：31.5 倍），这与农药的特定作用机制一致。基于作用模式特异性和受体复杂性的毒代动力学差异反映在敏感性变化的幅度上。然而，组织浓度的测量也表明，在解释毒死蜱和氯菊酯的物种敏感性变化时，毒动学可能具有重要意义。
