Toxicity assessment of naphthalene on Anabas testudineus

Naphthalene is a Polycyclic Aromatic Hydrocarbon (PAH) commonly used to make mothballs, insecticides, cleaning solutions and is an important component of petroleum and its by-products. PAHs enter the aquatic ecosystem through various routes and exert its effects on aquatic biota. In the present study naphthalene doses of varying concentration was tested for a period of 72 hours on Anabas testudineus and its toxicity was examined through biochemical and histological investigations. LC 50 was calculated to be 5.4mgl -1 using probit and graphical method. Experimental fishes were exposed to naphthalene dose concentration of 4.4 mgl -1 , 4.6 mgl -1 , 4.8 mgl -1 and 5 mgl -1 for a period of 72 hours and a parallel control set was maintained. Liver tissue was used to observe the changes incorporated as a result of naphthalene exposure. The glycogen content in muscle tissue of Anabas testudineus decreased with increase in the toxicant dose concentration in comparison to the control set. Decrease in the glycogen content is indicative of more carbohydrate utilization as a result of stress induced by the toxicant. Similar results were obtained for acid and alkaline phosphatases in experimental fishes. Reduction in ACP and ALP enzyme concentration in experimental fishes might be due to endoplasmic reticulum damage as a result of exposure to naphthalene. Different histopathological changes like vacuolization, necrosis, formation of intercellular spaces, swelling of hepatocytes and shifting of the nucleus towards periphery has been noticed in the liver tissue of experimental fishes. Change in the structural configuration of liver confirms and supports decrease in the concentration of glycogen and other marker enzymes like Acid phosphatase (ACP) and Alkaline phosphatase (ALP) on exposure to naphthalene.