Effects of Zn (NO3)2 on Liver tissue of Silver carp, (Hypophthalmichthys molitrix)

Zinc heavy metal was added as a micronutrient to water in order to increase of phytoplankton production and fish growth. By respect to feeding of silver carp from phytoplankton, the aim of this study is histopatological investigation of silver carp liver tissue that exposed to Zn (NO3)2 in farmed conditions. A totally of 135 fish with mean weight 50 ± 10 gr were stocked in 12 aquariums (with 200 liter capacity) and divided into 3 treatments such as 0, 0.5 and 10 mg/lit of Zn(NO3)2 concentration with 3 replicates in each trail including 15 fish in each aquarium. Sampling of livers was carried out at 12, 24, 48, and 72 and 96 hours after next to Zinc. After fixing of samples in Bruin's solution, they sectioned with 7 micrometer and stained with Haematoxilen and Eozin (H & E) method. Microscopically results showed cell atrophy and necrosis, hyperemia, fatty degeneration and bile stagnation disorders in 5 and 10 mg/lit treatments as comparison to control. Results showed that with increase of Zn (NO3)2 concentrations and duration next to Zn up to 96 hours, histopathological damages of liver was increased, so that damages severity was more at concentration 10 mg/l in 72 and 96 hours than other times and treatments