Synergistic impact of heavy metals (Ni and Hg) and histopathological alterations in the organ (gill) of the fish, Lates calcarifer (Bloch, 1790)

The specimens were exposed to sublethal concentration of individual and mixed metals viz., Nickel (4.0 ppm), mercury (3.5 ppm) and nickel plus mercury (3.0 ppm) for a period of 35 days. The gill samples were collected at 7 day interval for assessment of gill damage in the exposed fish. When the fish were exposure to above metal concentrations, several gill alteration were observed. The alteration was less in nickel concentration compared to mercury and nickel plus mercury concentration respectively. The fish exposed to nickel concentration, hypertrophy, necrosis and swollen tips of the primary lamellae and in mercury concentration hyperplasia and degenerative changes lamellae fusion were observed. In mixed metals concentration desquamated epithelium, necrosis and blousing at the tips of the secondary lamellae were exposed. The main histopathological changes observed in the gill were edema and lifting up of the epithelium, swelling, hyperplasia and hypertrophy but in mercury treatment, lamellar fusions, fusions, fused secondary lamella and necrosis were observed. This investigation presents a reliable indicator of the aquatic ecosystem contamination and the possible negative impact of the surrounding environment