The cytotoxic effect of the water-soluble fractions of crude oil in gills of Gafrarium divariratunl was studied histopathologically. The study, provides an insight into the extent of damage caused to the gill exposed for a period of 7, 14, 21 and 28 days to Various dilution concentrations of 10% stock water-soluble fractions (WSFs) of Bombay High (BH) crude oil. The gill exposed to low sublethal concentrations of 5 and 10 percent did not show much morphological alteration during 7 day exposure. Howeyer, after 21 days, fusion of adjacent lamellae was prominent in same concentrations due to advanced stage of hyperplasia. In 25% dilution concentration gills showed widening of water tubes, vacuolisation, clumping and bending of lamellae, etc. after 7days of exposure. In higher concentrations of WSF (50%. 75% and undiluted WSF) sloughing of lateral cells from the chitinous rods of gill filaments, desquamation in lamellae, and haemocytic infiltration were observed within 7days. Various groups of ciliary arrangements in the gills were uprooted; only the  chitinous supporting rods remained on 14^th day in 75% WSF dilution concentration.

Water-soluble fractions, crude oil, histopathological changes in gill, Gafrarium