EFFECTS OF WATER-POLLUTION ON THE GILL APPARATUS OF FISH

The study was designed to investigate the influence of water pollution on gill apparatus. Specimens of Nile tilapia were collected from a po lluted site in the Sao Paulo metropolitan area (Billings reservoir) an d from a ''clean'' area. Fish from the polluted site showed a chronic inflammatory process in the distal region of the gill filaments, with epithelial hyperplasia. The raker length was increased and hypersecret ion occurred, with a considerable volume of alcian blue-positive mucin on the epithelium of the rakers and a smaller volume of periodic acid -Schiff-positive mucin on the epithelial surface of the filaments. The rigidity of mucus in fish from the polluted site was increased, but n o abnormalities in the viscosity to elasticity ratio or in mucus ''wet tability'' were observed. (C) 1996 W.B. Saunders Company Limited