Histopathology alterations and lipid peroxidation as biomarkers of hydrocarbon-induced stress in earthworm, Eudrilus eugeniae Francis Joseph Eseigbe & Victoria Funmilayo Doherty & Temitope Olawunmi Sogbanmu & Adebayo Akeem Otitoloju Received: 23 August 2011 / Accepted: 28 May 2012 / Published online: 13 June 2012 # Springer Science+Business Media B.V. 2012 Abstract This study investigated the biomarker responses of the earthworm, Eudrilus eugeniae, exposed to sublethal concentrations of benzene, toluene and xy- lene (BTX) for a time span of 28 days. Lipid peroxidation (LPO) and histopathological alterations were examined. Toxicological evaluations of BTX were carried out against E. eugeniae. On the basis of the 96-h LC 50 value, xylene (1.212 mg/kg) was found to be the most toxic followed by toluene (1.335 mg/kg) and benzene (1.896 mg/kg) was the least toxic. The exposure of earth- worms to sublethal concentrations (1/10th and 1/100th of 96 h LC 50 ) of BTX premixed with the substrate (loamy and humus soil) induced pathological changes in the clitella such as severe lesion, necrosis and dark brown pigments. The result of the lipid peroxidation assay showed a significant increase in oxidative damage with LPO values ranging from 2.58–7.8 nM/g in exposed animals when compared to 0.07 nM/g in the control group. The findings from this study suggest the use of LPO and histopathology as useful biomarkers of expo- sure for early detection of petroleum related stress in terrestrial ecosystems Keywords Biomarkers . Earthworms . Histopathological alterations . Lipid peroxidation . Hydrocarbons Introduction Biomarkers can be sensitive indicators of sub-cellular stress in organisms exposed over short and longer periods to a range of pollutants (Adams et al. 2000). Earthworms are ideal as non-conventional organisms for assessing biological risks from hazardous and toxic wastes in ter- restrial environments (Callahan 1988). They can also be used as biomarkers and are often used extensively to document and qualify exposure to and effect of environ- mental pollutants. As monitors of exposure, they have the advantage of qualifying only biologically available pol- lutants, so these worms are seen as promoters of biore- mediation (Bouwman and Reineeke 1987). Tests on earthworms aim to evaluate their response at the individual or population level (community cen- sus analysis, nematode maturity index), assess the Environ Monit Assess (2013) 185:2189–2196 DOI 10.1007/s10661-012-2700-3 F. J. Eseigbe : T. O. Sogbanmu : A. A. Otitoloju Ecotoxicology Laboratory, Department of Zoology, University of Lagos, Akoka, Lagos, Nigeria F. J. Eseigbe e-mail: joseph2042003@yahoo.com T. O. Sogbanmu e-mail: topesho@gmail.com A. A. Otitoloju e-mail: aotitoloju@unilag.edu.ng V. F. Doherty (*) Department of Biological Sciences, Yaba College of Technology, Lagos, Nigeria e-mail: funmilayodoherty@yahoo.co.uk