Histopathological alterations in the cichlid fish Tilapia Zillii exposed chronically to the organophosphorus insecticide chlorpyrifos

ABSTRACT

The histopathological changes in gills and liver of the cichlid Fish Tilapia zillii were studied after exposure to two sublethal concentrations of the organophosphate insecticide chlorpyrifos for 90 days. Gills exposed to 1.7 micro g chlorpyrifos/1 revealed dilation of the blood vessels, tilangectasia in the secondary lamellae with slight prolifertive changes of the epithelial covering. At 3.6 micro g chlorpyrifos/1 a marked proliferative changes were found in the epithelium covering secondary lamellae and sometimes appeared hypertrophied with a marked increase in the number of mucus glands. There were no significant alterations in liver at the early stages of exposure to the sublethal concentrations of chlorpyrifos. Liver at 1.7 micro g/l showed vacuolar degeneration of hepatocytes together with activation of pancreatic acini. The hepatocytes appeared vacuolated and some of them were necrotized at 3.6 micro g chlorpyrifos/1