Gill histophatological alternation reduction in parrot fish (Cichlasoma synspilum ♀ × Cichlasoma citrinellum ♂) after exposure to water-born silver nanoparticle by feeding on astaxanthin and bile salt

This study aimed to investigate the effects of water-born silver nanoparticles (AgNPs) on gill histopathological alternation of Parrot and the possible protective effects of diet enriched with astaxanthin alone or in combination with bile salt. 200 Parrot fishes (average weight 25.5±6.2) were randomly distributed in three different groups: control (basic diet), astaxanthin alone (4g/kg) or in combination with bile salt (1200 mg/kg). The fish were fed for 90 days and then subjected to AgNPs, 250 μg/L for 5 days. The silver bioaccumulation and gill histopathology analysis were done before and after exposure period. The results showed significant increase in silver concentration in the gill tissues of the control group after AgNPs exposure (P0.05). After exposure to AgNPs, different gill histopathological alterations such as hyperplasia, hypertrophy, looping, necrosis and fusion were observed in fish from all treated groups, although the intensity of them were significantly lower in the groups of fish fed on astaxanthin alone or in combination with bile salt, comparison to the control group. In general, it can be concluded that diet enriched with astaxanthin alone or in combination with bile salt as antioxidant supplement can reduce the harmful effects of AgNPs on the gills.