Assessment of cytotoxicity in gills of fish Labeo rohita reared in untreated and treated sewage water.

Abstract

The unregulated discharge of untreated municipal sewage water to the natural water bodies is a major threat to the aquatic ecosystems. In the present study, the fingerlings of Labeo rohita were exposed to treated sewage water and 1/10th of LC50 and 1/20th of LC50 of untreated sewage water (UT) obtained from sewage water treatment plant, Ludhiana, India. After determining 96-h LC50 value of UT, fingerlings were divided into four groups: control, treated, 1/10th of LC50 UT and 1/20th of LC50 UT and exposed for a period of 2months. Our study revealed that 1/10th LC50 UT and 1/20th LC50 UT groups had significant reduction in body weight, total body length, standard body length and gills somatic index in comparison with the control and treated groups. Histopathological alterations in cellular structure of gills such as ruptured primary lamellae, broken secondary lamellae, distorted chloride cells and goblet cells, missing lamellae and disintegrated lamellar epithelium were also observed in 1/10th LC50 UT and 1/20th LC50 UT groups. A significantly high frequency of micronucleated (MN) cells was observed in 1/10th LC50 UT and 1/20th LC50 UT groups along with the presence of binucleated cells (BN), elongated nuclei (EN) and nuclear buds in gill cells. Genotoxic nature of UT was further confirmed from significantly high values of genetic damage index (GDI) and percentage (%) DNA damage in gill cells of fingerlings exposed to sub-lethal concentrations of UT. The study concluded that untreated sewage water has potential to induce anatomical and physiological defects in gills cells and the severity of toxicity increases with the increase in duration of exposure.