Department of Renewable Resources, University of Alberta, Edmonton, AB, Canada.
Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada.
Environ Sci Pollut Res Int. 2022 Nov;29(54):81740-81748. doi: 10.1007/s11356-022-21571-6. Epub 2022 Jun 23.
Thallium (Tl) is a trace metal enriched in wastewaters associated with mining and smelting of base metals. The toxicity of Tl to aquatic biota is poorly understood, particularly with respect to its sublethal effects. In this study, phototactic behavioural responses of naïve (i.e. no previous exposure to Tl) Daphnia magna, a key regulatory freshwater crustacean species, were examined in waters containing Tl. Fed and fasted neonate daphnids (< 24 h old) and fed adults (10-15 days old) showed no significant response at any tested water Tl concentration. However, in fasted adults, an increase in the positive phototactic response (measured as a greater number of daphnids closer to the light source after a 5-min exposure) was seen at Tl concentrations of 917 and 2099 µg L, values representative of extreme environmental Tl concentrations. The presence of Tl also decreased the swimming speed of adult Daphnia towards a light source. In the presence of cimetidine, a histamine receptor blocker, the increase in positive phototaxis induced by Tl disappeared, suggesting that Tl acts to perturb the phototaxis response through sensory inhibition. Conversely, although there was a trend towards enhanced activity, Tl had no significant effect on acetylcholinesterase, a marker of locomotor capacity.
铊（Tl）是一种痕量金属，在与贱金属开采和冶炼有关的废水中含量丰富。铊对水生生物的毒性知之甚少，特别是其亚致死效应。在这项研究中，研究了未接触过铊（即没有以前接触过铊）的大型溞（Daphnia magna）的趋光行为反应，大型溞是一种关键的淡水甲壳类调节物种，在含有铊的水中进行了检测。喂养和禁食的幼体大型溞（<24 小时龄）和喂养的成体（10-15 天龄）在任何测试的水中铊浓度下均没有表现出明显的反应。然而，在禁食的成体中，在铊浓度为 917 和 2099 µg L 时，观察到正向趋光反应（表现为在 5 分钟暴露后更靠近光源的大型溞数量增加）增加，这些浓度值代表了极端环境中的铊浓度。铊的存在也降低了成年大型溞向光源的游动速度。在西咪替丁（一种组胺受体阻滞剂）存在的情况下，铊诱导的正向趋光性增加消失，这表明铊通过感觉抑制来干扰趋光反应。相反，尽管活动有增强的趋势，但铊对乙酰胆碱酯酶（运动能力的标志物）没有显著影响。
