Abstract

Zinc is one of an environmental water pollutant, added to diet and water as a micronutrient for increase of plankton production and fish growth. Therefore, this research was carried out with the aims of studying on histopathology of Zn(NO₃)₂toxicity on gill and liver tissues of silver carp (Hypophthalmichthys molitrix) within the period of 96 h. Totally, 135 fishes with mean weight 50 ± 10 g were stocked in 12 aquariums with capacity of 200 L water and divided in to 3 trails including control, 5 ppm and 10 ppm of Zn with 3 replicates. Tissue samples were fixed by buin’s solution and sectioned in 7 µm based on histological regular method and stained with Hematoxilen and Eosin (H & E) method for microscopic study within the period of 96 h. Results showed some damaged such as hyperplasia, telangiectasis and edema, necrosis of second filaments, jerky movement, aneurism, hyperemia and fusion of second filaments in gills; and cell atrophy, necrosis, fatty degeneration, hyperemia and bile stagnation at different treatments in comparison with control. Gill and liver tissue damages were severed with the increase of Zn concentration and days. Therefore, Zn had acute toxicity effects on gill and liver tissues in Silver Carp at 5 and 10 ppm concentrations.

Key words: Silver carp, Zn, gill, liver and histopathology.