عنوان مقاله [English]
In the past years due to increasing use of nanoparticles, concerns have been raised worldwide regarding their environmental impacts. In aquatic animals, the gill has an external position and a wide contact surface with water, it directly comes into contact with pollutants. Therefore, examining the changes occurring in the gill tissue is an appropriate indicator for assessing the effects of pollutants. For this research, the common carp fingerling fish with 15±3 g weight were divided into 9 treatments (with three replicates) with a density of ten fish per 300-liter tank. Based on lethal concentrations, the concentrations were considered as 0 (control treatment), 0.5, 1.5, and 2 ppm for ZnO nanoparticles, and 3, 6, and 9 ppm for TiO2 nanoparticles, as well as combined concentrations. The concentrations of zinc oxide and titanium dioxide nanoparticles were 0.5 and 3, 1.5 and 6, and 2 and 9 ppm, respectively. Gill tissue samples of the examined carp were separately and simultaneously exposed to zinc oxide and titanium dioxide nanoparticles after 14 days. Histological changes in the gill tissues were evident in samples exposed to ZnO and TiO2 nanoparticles separately, while no changes were observed in the control samples. The observed changes in samples exposed to ZnO nanoparticles included hyperplasia, fusion of gill filaments, bending of gill filaments, protrusion and twisting of the epithelial layer, disintegration of the epithelial layer, shortening of secondary gill filaments, and destruction of secondary gill filaments, which were more pronounced with increasing concentrations. Samples exposed to TiO2 nanoparticles showed hemorrhage, increased epithelial cells, and destruction of secondary gill filaments. Gill tissue exposed to ZnO nanoparticles showed more damage compared to titanium dioxide nanoparticles. Furthermore, samples simultaneously exposed to TiO2 and ZnO nanoparticles exhibited changes such as hemorrhage, hyperplasia, fusion of gill filaments, bending of gill filaments, protrusion of the epithelial layer, disintegration of the epithelial layer, shortening of secondary gill filaments, and increased epithelial cells. According to the results obtained, it was observed that ZnO nanoparticles had more harmful effects compared to TiO2 nanoparticles. Moreover, these damages to the gill tissue intensify and have mutual effects when simultaneously exposed to TiO2 and ZnO nanoparticles.