Histopathological and Biochemical Changes in the Gills of Anabas testudineus on Exposure to Polycyclic Aromatic Hydrocarbon Naphthalene.

Naphthalene, a polycyclic aromatic hydrocarbon, is generated by various distillation, petroleum, and coal-tar production units and is used worldwide as mothballs, soil fumigants, and toilet deodorants. Considering the susceptibility of aquatic animals to different types of stressors in several water bodies, this study was carried out to evaluate the impact of naphthalene on the architecture of gill tissue including response of various enzymes like cholinesterase (ChE) activity, lactate dehydrogenase (LDH) activity, and lipid peroxidation (LPX) level of the freshwater fish Anabas testudineus. Activities of antioxidants like catalase (CAT), glutathione peroxidase (GPx), and glutathione (GSH) were also evaluated. Constant loss of gill structure and secondary lamellar fusion was observed in fishes exposed to various concentrations of naphthalene. ChE, LDH, LPx, CAT, Gpx and GSH activities indicated significant variation (p < 0.05) between the control and experimental groups. ChE activity was lowered in experimental fishes; however, LDH activity, LPx levels, and CAT activity were elevated in response to various concentrations of naphthalene as compared to control group. Both GPx and GSH activities decreased in the gill tissue of the experimental fishes. Thus, a conclusion was drawn that naphthalene is a potent toxicant capable of inflicting tissue damage leading to physiological changes in the exposed fishes.

Role of Integrated Biomarker Response Tool for Assessment of Naphthalene Toxicity in Anabas testudineus.

Polyaromatic hydrocarbons are highly stable and can easily permeate through biological membranes due to their lipophilic nature. They are characterized by their ability to act at the site of application and even at sites distant to the zone of application. Any contamination associated with aquatic bodies due to the presence of PAHs can be assessed by investigating biochemical changes. The most common polycyclic aromatic hydrocarbon (PAH) pollutant naphthalene was selected for the bioassay experiment using Indian climbing perch Anabas testudineus. The biochemical response in the muscle tissue was investigated after exposure to varying concentrations of naphthalene by estimating protein, glycogen, Alanine Aminotransaminase, and Aspartate Aminotransaminase. The results showed inhibition of protein and glycogen levels due to naphthalene stress. Similarly, a decrease in the activity of transaminase in muscle tissues was noticed. The results have been computed using star plots for interpretation of integrated biomarker response (IBR). The results clearly support the role of biochemical parameters in assessing the impact of naphthalene stress on fish health. IBR index can be developed as a useful tool in monitoring quantitative as well as the qualitative effect of naphthalene toxicity in fishes and other aquatic animals.