ultrastructural changes in the gills of a cyprinid fish, labeo rohita (hamilton, 1822) through scanning electron microscopy after exposure to lead nitrate (teleostei: cyprinidae)

labeo rohita fingerlings were reared in freshwater and exposed to different concentrations of lead nitrate. after the exposure, one fish was sacrificed from each dose and the gill arches were removed. the ultrastructural changes on the gills of this cyprinid fish were investigated through scanning electron microscope (sem). lead treated gill tissues showed certain marked changes such as uplifting, hyperplasia and fusion of the secondary lamellae, swollen and distorted pavement cells, broken and swollen microridges, broken tips and upliftment of gill rakers, cellular extrusions, heavy exudation of mucous, disorganisation of secondary lamellae, etc. the changes were more rapid and intensive at higher concentrations as compared to lower concentration revealing that the alterations caused in the tissues of gills are highly dose dependent.