Biomarker Responses of Zinc on Orange Chromidae (Etroplus Maculatus, Bloch, 1795)

The contamination of the aquatic systems with heavy metals from natural and anthropogenic sources has become a global problem which poses serious threats to ecosystems and natural communities. Acute and chronic toxicities of zinc on teleost fish, Etroplus maculatus and its histopathological impacts on gill and liver tissue were evaluated. The median lethal concentration (96 h, LC50) of zinc was calculated as 12.4mg/l by static renewal test method. The fish were exposed to two sub-lethal concentrations of zinc (0.826 mg/l and 2.48mg/l) and gill and liver samples were collected after 14 and 28days of exposure. The structural deformities observed in gills were characterized by epithelial lifting and oedema, lamellar fusion, desquamation and necrosis, whereas, the liver tissue showed swelling of hepatocytes, vacuolar degeneration, focal necrosis, nuclear hypertrophy and cirrhosis with acute hemorrhage. The histopathological change indicates the possibility of bioaccumulation of zinc in the trophic levels of the ecosystem.