Mercury (Hg) contamination is a major environmental concern that continuously impacts marine organisms, including the mangrove horseshoe crab (Carcinoscorpius rotundicauda). As a vulnerable species, C. rotundicauda holds significant ecological and evolutionary value, making it particularly susceptible to Hg pollution and deserving of focused conservation efforts. This study presents the first comprehensive histopathological and histochemical analysis of mercury toxicity in the digestive tract of adult C. rotundicauda. Through both qualitative and quantitative analyses of histopathological and histochemical alterations, we evaluated the effects of acute Hg exposure (0.5 mg/L and 5 mg/L) on the esophagus, stomach, and intestines over time. The results revealed significant dose- and time-dependent tissue damage, with the stomach exhibiting the most pronounced alterations, including epithelial detachment, vacuolation caused by fibers degradation in the loose connective tissue, and muscle layer disruption, followed by the esophagus and intestines. Additionally, mucous cell density in the hindgut submucosa decreased by 30 % after 96 h of acute Hg exposure (0.5 and 5 mg/L HgCl2), indicating a weakened protective barrier. The tissue damage of the digestive tract may further have a negative impact on the health of the adult horseshoe crab, thus threatening the survival of C. rotundicauda population and reducing the biodiversity of the mangrove ecosystem. These findings underscore the critical threat posed by Hg pollution to the digestive system of C. rotundicauda and offer novel insights into the toxicological impact on marine invertebrates. Considering the tissue-damaging effects of Hg on adult horseshoe crabs, this study underscores the importance of regular monitoring of Hg contamination in natural habitats. The results offer valuable guidance for future habitat restoration and effective management of existing habitats.

中文翻译：

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汞胁迫下成鱼鲎消化道的组织病理学和组织化学分析


汞 （Hg） 污染是一个主要的环境问题，持续影响海洋生物，包括红树林马蹄蟹 （Carcinoscorpius rotundicauda）。作为一种脆弱的物种，C. rotundicauda 具有重要的生态和进化价值，使其特别容易受到汞污染，值得重点保护。本研究首次对成年 C. rotundicauda 消化道中的汞毒性进行了全面的组织病理学和组织化学分析。通过对组织病理学和组织化学改变的定性和定量分析，我们评估了急性汞暴露 （0.5 mg/L 和 5 mg/L） 对食管、胃和肠道随时间推移的影响。结果显示显着的剂量和时间依赖性组织损伤，胃表现出最明显的改变，包括上皮脱离、松散结缔组织中纤维降解引起的空泡化和肌肉层破坏，其次是食道和肠道。此外，急性汞暴露 96 小时后，后肠粘膜下层粘膜中的粘液细胞密度下降了 30%（0.5 和 5 mg/L HgCl2），表明保护屏障减弱。消化道的组织损伤可能进一步对成年马蹄蟹的健康产生负面影响，从而威胁到马蹄蟹种群的生存，并减少红树林生态系统的生物多样性。这些发现强调了汞污染对 C. rotundicauda 消化系统构成的严重威胁，并为对 C. rotundicauda 的毒理学影响提供了新的见解。 考虑到汞对成年马蹄蟹的组织破坏作用，本研究强调了在自然栖息地定期监测汞污染的重要性。研究结果为未来的栖息地恢复和现有栖息地的有效管理提供了有价值的指导。