Biochemical and histopathological effects in muscular tissue of carp fish (Labeo rohita, Hamilton 1822) following exposure to untreated and treated sewage water.

Present work describes a laboratory study aiming at assessing the impact of sewage treatment plant (STP) effluents on fish health by means of biochemical and histopathological biomarkers in muscular tissue of fish. Labeo rohita (7.62 ±0.25 cm, 8.25±0.32 g) was exposed to sub-lethal concentrations of untreated (UT) and treated (T) sewage water obtained from STP, Ludhiana, India. Following the determination of the 96h lethal concentration (LC), the fish were exposed to control (de-chlorinated tap water), treated sewage water, 1/10 of LC UT and 1/20 of LC UT sewage water. The experiment was conducted for the period of 60 days. Experimental results depicted significant reduction (p<0.05) in muscle-somatic index of 1/10 LC UT and 1/20 LC UT groups compared to control and treated groups. Fish toxicity induced by untreated sewage water was evident from the significant decrease (p<0.05) in the levels of proteins and significant increase (p<0.05) in content of total lipids in muscular tissue of exposed group fingerlings. Drastic changes in the fatty acids profile and severe histological abnormalities viz. shortening of muscle bundles, edema, hyper-vacuolization, elongation of muscle bundles, gap formation in myofibrils, degenerated myotomes, hemorrhage, inter-myofibrillar space, necrosis, were also recorded in muscular tissue of exposed fingerlings. The intensity of muscular damage in L.rohita was found to increase with increase in duration of exposure. Results demonstrated that untreated sewage water could potentially induce physiological stress and somatic cell toxicity in fish L.rohita. Genotoxicity studies on germ cells of L.rohita fingerlings are further suggested to examine the genotoxic potential of untreated sewage water at high concentrations; this is especially of interest given that many effluents are genotoxic to fish.