Histochemical and histopathological study of the intestine of the earthworm (Pheretima elongata) exposed to a field dose of the herbicide glyphosate

Histopathological and histochemical variations in non-specific esterases of the intestinal epithelial lining of the earthworm (Pheretima elongata), exposed to a single field dose of the herbicide glyphosate, were studied on the first, second, third, and fourth week of exposure. A severe cell death was observed in the intestine during the first and second weeks of exposure and mortality exceeded 50 percent. In the third week of exposure, the cells of the intestinal lining of the worms which had survived started regenerating and in the fourth week of exposure the epithelial lining regained its original characteristics and architecture, suggesting the high regenerative power of earthworms. Non-specific esterases showed an intense activity in the first week of the exposure and then decreased in the second week to nearly a minimum, where the entire cell structure was lost. However, the activity of the enzyme remained low until the third week where there was a small rise in the activity, and was confined to certain places in the cytoplasm. In the fourth week, almost a complete regeneration of the epithelial lining as well as the non-specific esterases activity was observed and became quite similar to that of the control worms. These results suggest that glyphosate, even at the recommended field dose, could cause cell death and interfere with non-specific esterases activity of the epithelial lining of the intestine of P. elongata causing at least 50 percent mortality in the population of the worms.