Effects of iron and silver nanoparticles on Ctenopharyngodon idella's swimming performance, their bioaccumulation,...

Nanoparticles (NPs) are small-sized particles that have various applications; however, these metallic particles are found to be toxic against aquatic organisms. Therefore, the current study observed the toxicity of silver nanoparticles (AgNPs) and iron oxide nanoparticles (IONPs) using Ctenopharyngodon idella by swimming behavior, bioaccumulation, histopathological alterations, and oxidative stress. Fish were exposed to AgNPs and IONPs (5.16 mg/L) for 10 days to assess their possible effects on behavioral and physiological changes. Results showed that both NPs significantly decreased the critical swimming speed (U_crit), and found a significant correlation between body size and swimming speed. The NPs were significantly accumulated in the intestine, followed by muscles, gills, liver, and brain (p < 0.05), which resulted in histological alterations, i.e., necrosis in gill lamella and grey matter disruption in brain. In addition, the NPs resulted in oxidative stress, i.e., the superoxide dismutase enzyme in the gill was significantly increased (291.66 ± 4.04) in the IONPs group. The possible mechanisms include NP-induced gill damage and altered gill morphology, which may impair respiratory efficiency, ROS, and osmoregulation, leading to reduced swimming performance.