LAUSR

Different types of metal oxide nanoparticles (NPs) have been suggested for various applications such as water treatment and construction of agricultural pesticides; however, there are concerns about the potential toxicity of these compounds for the nontarget organism especially aquatic organisms. The aims of this study were assessing toxicity and histopathological effects of copper oxide NPs (NPs‐CuO) on common carp (Cyprinus carpio) as a model organism. For this purpose 150 common carp with an average weight 7 ± 1 g were exposed to 0, 10, 20, 30, 40, 60, 80, 100, 150, and 200 mg/l of CuO‐NPs (10 treatment with three replicates) for 96 hrs. After 24, 48, 72, and 96 hrs exposures, mortality rates recorded and gill samples were collected. Statistical analysis showed significant differences in carp survival between control and treatment groups (p < 0.05); regression between fish mortality rate and NPs‐CuO concentration was also revealed (p < 0.01). The LC50 96h of NPs‐CuO for common carp was estimated as 124.9 mg/l in this study. Various tissue damages were observed in gill of treatments; such as, hypertrophy, hyperplasia, lamellar fusions, erythrocyte infiltration, epithelial lifting; also, there was significant correlation between intensity of tissue lesions and concentration of NPs‐CuO (p < 0.01). The findings of the present study demonstrate that sublethal concentration of NPs‐CuO can lead to serious tissue lesions. Whats more, concentrations above 30 ml/l of NPs‐CuO can lead to some clinical signs; such as skin darkening and death with open mouth as well as definite fish death.