Haemato-immunological studies in ZnO and TiO2 nanoparticles exposed euryhaline fish, Oreochromis mossambicus

•ZnO and TiO2 nanoparticles exposed groups showed decreased red blood cells in Oreochromis mossambicus.•Treated groups showed elevated white blood cells due to their enhanced immunological responses.•Leucocytes and lymphocytes showed increased phagocytic activities towards the nanoparticles. The present study was aimed to analyze the effect of ZnO and TiO2 nanoparticles (NPs) on Haemato-immunological parameters in adult Tilapia, Oreochromis mossambicus. The nanoparticles size found as 47 nm and 30 nm for ZnO and TiO2 respectively. The acute toxicity (96 h) of ZnO (LC50: 100–110 ppm) and TiO2 (LC50: 80–90 ppm) NPs were identified by using probit analysis. RBC, Hb and HCT levels decreased in nanoparticles exposed groups resulted in decreased oxygen carrying capacity of RBC and other erythrocyte indices (MCH, MCV, MCHC). Increased WBC, neutrophils & monocytes and decreased lymphocyte levels were observed as increased concentration of the nanoparticles. The results were found as statistically significant (p