10th U6+ Consortium of African Universities International Conference

The emergent nanoparticles (ZnO-NPs) have detrimental effect on aquatic organisms when indiscriminately discharged into water body. Accumulation of these nanoparticles in fish tissues could have potential adverse effects on vital organs in fish. The histopathological effect of ZnO-NPs on the endocrine glands and implication on hormonal levels and growth responses of juveniles of hybrid catfish, Heteroclarias were investigated in this study. The fish were assessed in static renewal bioassay for the period of 28 days under standard laboratory condition in four different concentrations (0.00 mg/l, 8.00 mg/l, 16.00 mg/l and 24.00 mg/l) of ZnO-NPs. At the end of the exposure period, both the control and the exposed fish were sacrificed after 28 days to remove the brain, ovary and the testis for histopathological assay, while the blood was collected for hormonal levels assay. Varying histopathological alterations such as enlarged pyramidal cells, neuronal cell degeneration, necrosis of brain cells, vacuolization with shedding of epithelial cells in the brain; loss of spermatogenic cells and atrophy in the seminiferous tubules, appearance of cell apoptosis and degeneration of tubular epithelium in the testis; degenerated vitellogenic oocytes and necrosis of oocytes in the ovary of ZnO-NPs exposed fish. There was decrease in growth and reproductive hormones with a significant reduction (P < 0.05) in the growth rate and specific growth rate. The results of this finding indicated that sub-lethal concentration of ZnO-NPs caused damage to endocrine glands that interrupted the functioning of the glands in the juveniles of Heteroclarias.