Although iron oxide nanoparticles (IONPs) have been widely used in nanomedicine and nanoremediation, their ecotoxicological effects on aquatic organisms remain unclear. In this study, the melanomacrophage center (MMC) response and hepatic histopathologic biomarkers were investigated in female guppies, Poecilia reticulata, exposed to citrate-functionalized IONPs (γ-Fe₂O₃) at an environmentally relevant iron concentration (0.3 mg L⁻¹) over 21 days. The animals were collected at the beginning of the experiment and after 3, 7, 14, and 21 days of exposure. Guppies exposed to IONPs showed increases in the number, area, and perimeter of MMC when compared with the unexposed ones, especially after 7 days of exposure. The results showed an increase in the frequency of histopathologic changes in fish after 7 days of exposure to IONPs, such micro- and macro-vesicular steatosis, melanomacrophage aggregates, exudate, and hemorrhagic foci. The acute (3 and 7 days) and long-term (14 and 21 days) exposure of P. reticulata to IONPs induced high histopathologic indexes associated with circulatory disorders and inflammatory responses. Results showed that the MMC response and histopathologic index are important biomarkers to indicate the environmental impact of IONPs, confirming that the guppy P. reticulata is a target of ecotoxicity of IONPs.

尽管氧化铁纳米颗粒（IONPs）已被广泛用于纳米药物和纳米修复，但是它们对水生生物的生态毒理作用仍不清楚。在这项研究中，melanomacrophage中心（MMC）响应和肝组织病理学的生物标记物在雌性孔雀鱼，进行了调查孔雀鱼，暴露于柠檬酸官能化的IONPs（γ-的Fe ₂ ö ₃在一个环境相关的铁浓度（0.3毫克L）^-1）超过21天。在实验开始时以及暴露后3、7、14和21天后收集动物。与未暴露的孔雀鱼相比，暴露于IONP的孔雀鱼的MMC数量，面积和周长有所增加，尤其是在暴露7天后。结果显示，暴露于IONP 7天后，鱼类的组织病理学改变的频率增加，例如微泡和大泡脂肪变性，黑色素巨噬细胞聚集体，渗出液和出血灶。网纹假单胞菌的急性暴露（3天和7天）和长期暴露（14天和21天）IONPs引起的高组织病理学指标与循环系统疾病和炎症反应有关。结果表明，MMC反应和组织病理学指标是表明IONPs对环境的影响的重要生物标志物，证实了孔雀鱼P. reticulata是IONPs生态毒性的目标。