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Abstract
The acute toxicity level of Forcados light crude oil against earthworm Eudrilus eugeniae was 10.33ml/kg based on the 96hr LC50 value. The exposure of the earthworm to sublethal concentrations (1.032ml/kg and 0.103ml/kg) of crude oil resulted in the exhibition of coiling responses, weight loss and swollen clitellum region in exposed animals. Studies on the total haemocyte counts in blood of the earthworms also showed that there was a reduction in the total haemocyte counts in the exposed animals compared to the control organisms. The significance of these sublethal effects particularly its importance as useful stress indicators to identify and assess recovery of crude oil contaminated ecosystems were discussed.
Keywords: Earthworm, crude oil, stress indicators, sublethal effect, toxicity,