Yu_2026_Fish.Shellfish.Immunol_170_111139

Crucian carp (Carassius carassius) were exposed to polyethylene microplastics (PE-MPs) at concentrations of 0, 4, 8, 16, 32, and 64 mg/L for two weeks. The experimental fish had a mean weight of 23.2 +/- 3.1 g and a mean length of 12.1 +/- 0.9 cm. Exposure to <=32 mg/L PE-MPs caused significant increases in cortisol and HSP70 levels, indicating activation of endocrine and cellular stress responses. In contrast, immune parameters such as lysozyme activity and IgM concentrations were significantly reduced, demonstrating suppression of both innate and adaptive immune functions. Moreover, acetylcholinesterase (AChE) activity was significantly inhibited, reflecting impaired cholinergic neurotransmission and neurotoxicity. Integrated biomarker response (IBR) analysis revealed concentration-dependent alterations, while heatmap and principal component analyses (PCA) confirmed that PE-MPs predominantly induced stress-related physiological responses. Collectively, these findings demonstrate that exposure to <=32 mg/L PE-MPs poses significant physiological and neuro-immunotoxic risks to C. carassius.