J.C. KALITA, B.K. BARUAH*, R. AHMED*, S.K. CHOUDHURY* AND M. DAS**
Abstract
City sewage consists of all types of waste water including domestic, municipal and industrial waste and is highly polluted in terms of physical, chemical and biological characteristics. In the present investigation, aquatic typical fish Heteropneustes fossilis was treated in the sewage of Guwahati city for a period of 180 days and the histology of gill was studied after every 30 days interval. The gill showed remarkable changes in its histology showing vacuolation, hemorrhage and rupture of gill lamellae thereby impairing gaseous exchange mechanism in the fish.