Thimerosal (THI) has become a significant source of organic mercury pollutants in aquatic ecosystems, but there is limited information regarding its adverse effects on fish. In this study, zebrafish embryos were exposed to THI at 0 (control), 5.0, and 50 ng/L from 0–5 days post fertilization (dpf), and variations in their survival, development, behavior, free amino acid contents, and the biochemical responses involved in monoaminergic systems were examined. Although THI exposure did not significantly affect the survival, heart rate, or hatching time of zebrafish embryos, it substantially increased swimming velocity (136–154 % of the control) and reduced exploratory behavior (141–142 % of the control) in zebrafish larvae at 5 dpf. Exposure also significantly altered the amino acid contents (51–209 % of the control) and monoamine levels (70–154 % of the control) in zebrafish larvae, some of which displayed significant correlations with behavioral traits. THI significantly elevated dopamine receptor gene expression and monoamine oxidase activity in zebrafish larvae. Adding extra phenylalanine or tryptophan to the E3 medium facilitates the recovery of zebrafish larvae from the abnormal behaviors induced by THI. These findings reveal for the first time that THI exposure at the level of ng/L is sufficient to induce neurobehavioral toxic effects in the early life stages of zebrafish, and disrupting amino acid homeostasis is a critical underlying mechanism. This study provides valuable insights into the toxicity of THI to fish and highlights the importance of assessing its potential risks to aquatic ecosystems.

中文翻译：

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暴露于硫柳汞通过改变氨基酸稳态而导致斑马鱼生命早期阶段的行为异常


硫柳汞 (THI) 已成为水生生态系统中有机汞污染物的重要来源，但有关其对鱼类不利影响的信息有限。在这项研究中，斑马鱼胚胎在受精后 0-5 天 (dpf) 期间暴露于 0（对照）、5.0 和 50 ng/L 的 THI，观察其存活、发育、行为、游离氨基酸含量和检查了单胺能系统中涉及的生化反应。虽然 THI 暴露并没有显着影响斑马鱼胚胎的存活率、心率或孵化时间，但它显着增加了斑马鱼幼虫的游泳速度（对照的 136-154%）并减少了探索行为（对照的 141-142%） 5 dpf。暴露还显着改变了斑马鱼幼虫的氨基酸含量（对照的 51-209%）和单胺水平（对照的 70-154%），其中一些与行为特征显着相关。 THI 显着提高了斑马鱼幼虫的多巴胺受体基因表达和单胺氧化酶活性。在 E3 培养基中添加额外的苯丙氨酸或色氨酸有助于斑马鱼幼虫从 THI 诱导的异常行为中恢复。这些发现首次揭示，ng/L水平的THI暴露足以在斑马鱼生命早期阶段诱发神经行为毒性作用，而破坏氨基酸稳态是一个关键的潜在机制。这项研究提供了有关 THI 对鱼类毒性的宝贵见解，并强调了评估其对水生生态系统潜在风险的重要性。