Histopathological Studies of Some Organs of Grass Carp (Ctenopharyngodon idella) Exposed to Sublethal Concentrations of Diazinon

Background and Diazinon is a widely used organophosphorus pesticide around the world especially in rice paddy fields. Some studies showed that such toxic chemicals can influence the health conditions of fish at various levels including fish immune system and increase the fish susceptibility to infectious diseases. In this study, histopathological effects of different sublethal concentrations of diazinon at 1, 2 and 4 mg/L were investigated on gills, liver, spleen, kidney and nostril of grass carp (Ctenopharyngodon idella). One hundred and twenty grass carps weighing 850±155 g were studied at 1, 7, 15, 30 and 45 days post-exposure to the toxicant for 12 hours at 18- 22ºC. Light microscopic examinations of tissues showed that toxicant concentrations caused severe damages to the cells and tissues structure such as congestion of blood vessels, haemorrhage, cellular infiltration, pyknosis of cells nuclei, vacuolar degeneration and general necrosis in the tissues of kidney, spleen and liver. There were degenerative changes of interstitial tissue and detachment of tubular basement membrane in kidney. We also observed hyperplasia and fusion of secondary lamellae, separation and sloughing of epithelium from the underlying basement membrane in gill sections and denudation of epithelial surface in nostril.