This study evaluated the effects of varying concentrations of silver nanoparticles (Ag-NPs) on the histopathology and immune response of Labeo rohita. A total of 120 fish (average weight 30.00 ± 1.45 g) were divided into four treatment groups (N0 = 0 NPs, N1 = 5 mg/L NPs, N2 = 10 mg/L NPs, and N3 = 20 mg/L NPs), each with three replicates. Ag-NPs were synthesized from the guava plant (Psidium guajava) and confirmed using X-ray diffraction analysis. The fish were fed isonitrogenous (30.00%) diets for eight weeks, with Ag-NPs administered through the water. The results indicated that higher Ag-NP concentrations led to significant abnormalities in gill and muscle tissues. Haematological parameters were significantly lower (P<0.05) in nanoparticle-exposed groups, except for glucose, which increased. Enzymes such as superoxide dismutase and catalase were elevated in treated groups, while triglycerides, liver enzymes, and malondialdehyde levels were significantly higher (P<0.05). The study concluded that Labeo rohita is highly sensitive to Ag-NP toxicity, particularly at 20 mg/L, resulting in reduced erythrocytes, haematological abnormalities, leucocytosis, and stress, making it an effective model for evaluating nanoparticle-induced toxicity.

Keywords: Ag-NPs, Immune response, Psidium guajava, Growth rate, XRD