Metallothioneins, Oxidative Stress Responses and Histopathological Changes in the Earthworm (Aporrectodea Caliginosa) in Metal Contaminated Agricultural Soils of Sakarya River Basin (Turkey)

Abstract

Metal accumulation in agricultural soils threaten human and environmental health in the first place but also constitute a risk for animals living in their natural habitat. Chemical analysis alone does not provide adequate information concerning the biotoxicity of these metals. Hence, the present study assessed a suite of biomarkers in Aporrectodea caliginosa collected from ten sampling sites along Sakarya River Basin (Turkey) to better understand the early organismal responses of this worm against metal contamination in agricultural soils. Soil and earthworm concentration of metals (Cd, Cr, Cu, Ni, Pb and Zn) were determined. Significant accumulation of Cd, Cr, Cu and Ni were detected in soil samples. Metal binding protein, metallothionein (MT), increased in four sites with the highest body burden of Zn. Total glutathione (GSH) and glutathione peroxidase (GPx) activity elevated but catalase (CAT) was inhibited in animals from six sites with significant body burden of Cu. Glutathione S-transferase (GST) and superoxide dismutase (SOD) activities were induced in most sites along with peroxidation of tissue lipids. Necrosis was observed in alimentary canal of the worms. These results constitute useful endpoints for the evaluation of biotoxicity of metals in agricultural soils while emphasizing A. caliginosa as a sensitive indicator of metal contamination.