ABSTRACT
This study was carried out to investigate the toxicity of Roundup, aglyphosate-containing herbicide to the earthworm Nsukkadrilus mbae and the associated histological changes. One hundred and sixty five earthworms were randomly divided into five groups and exposed to different concentrations of glyphosate (0.0, 13.0, 52.0, 117.0 and 207 mg/Kg soil) for 96 h. The mortality was recorded every 24h and after 96 h, sections of the earthworm from each treatment group were prepared for microscopic examination. There was no mortality in the control group and the survivors in the treatment groups were weak. The percentage mortality was least after 24 h and highest after 96 h and the mortality was significantly different (P = 0.05) in the groups except after 24h. The survival rate was generally concentration and duration dependent. The 96 h LC50 value was 10.4 mg/Kg soil. The observed histopathological changes included rupture of the cuticullar wall, tissue necrosis and prominent vacuolations. The circular and longitudinal muscle layers had altered structural integrity. These histopathological end points could be useful biomonitors of glyphosate toxicities in ecotoxicological studies involving earthworms.