The present study has investigated the toxic effect of monocrotophos on the intestine of the earthworm L. mauritii in a laboratory experiment. A sub-lethal concentration of monocrotophos (1/3rd of 96 h LC 50 value - 0.311 ppm) was applied for 30 days. The changes such as vacuolization, degenerated nuclei, damaged epithelial lining of villi and congestion of blood sinuses were observed in the intestine of 1st and 5th day of monocrotophos exposure. In the 30th day of exposure, slight damages were observed. These results suggest that monocrotophos could severely affect the intestine of 1st and 5th day of L. mauritii’s when compared to 30th day. This study indicates the importance of histopathological bioassay as an indicator of environmental pollution.
