Todays, with the industrialization of human societies, pollution of aquatic ecosystems with plastics derivatives are a serious concern, affecting the life of their organisms. The present study was conducted to investigate the size effects of micro-plastic, polystyrene on some physiological lesions of the goldfish, Carassius auratus. Fish were exposed to two sizes (0.25 and 8 μm) polystyrene at different environmentally relevant concentrations. The exposure trial was done in two steps. First, fish exposed to a stable concentration of 300 μg/L polystyrene for 168 h. Gill, intestine, and liver tissues were sampled every 24 h to investigate the accumulation of polystyrene. Then, fish were exposed in three replicates to 0 (control), 0.05, 0.5, and 5 mg/L polystyrene in two sizes of 0.25 and 8 μm for 28 days. After the exposure period, gill, liver, and intestine tissues were sampled for histological study, also, serum samples were collected for biochemical assays. Fluorescent microscope observations confirmed the accumulation of polystyrene in tissue samples with time. In addition, histological lesions were found in the liver, intestine, and gill of the exposed fish. The severity of lesions showed a size and dose-dependent pattern. Polystyrene induced the antioxidant system of exposed fish through elevating the levels of SOD and CAT activity and significant difference in expression of antioxidant related genes (CAT, SOD and HSP70). In conclusion, the results of the present study confirmed the toxic effects of microplastic, polystyrene on goldfish.

当今，随着人类社会的工业化，塑料衍生物对水生生态系统的污染已成为一个严重问题，影响了其生物的生命。本研究是为了研究微塑料，聚苯乙烯上的金鱼的一些生理病变的大小的影响，鲫鱼。鱼在不同的环境相关浓度下暴露于两种尺寸（0.25和8μm）的聚苯乙烯中。暴露试验分两个步骤进行。首先，将鱼暴露于稳定浓度为300μg/ L的聚苯乙烯168小时。每24小时取样，肠和肝组织，以调查聚苯乙烯的积累。然后，将鱼一式三份暴露于0（对照），0.05、0.5和5 mg / L两种尺寸为0.25和8μm的聚苯乙烯中28天。在暴露期之后，对腮，肝和肠组织进行采样以进行组织学研究，并且还收集血清样品以进行生化测定。荧光显微镜观察证实了组织样品中聚苯乙烯随时间的积累。此外，在裸露的鱼的肝脏，肠和g中发现了组织学损伤。病变的严重程度显示出大小和剂量依赖性模式。聚苯乙烯通过提高SOD和CAT活性水平以及抗氧化剂相关基因（CAT，SOD和HSP70）表达的显着差异来诱导裸露鱼类的抗氧化系统。总之，本研究的结果证实了微塑料，聚苯乙烯对金鱼的毒性作用。