Responses of the earthworm Eisenia andrei exposed to sublethal aluminium levels in an artificial soil substrate

Abstract

Industrial discharges of Al are increasingly common. In this study, the activities of three antioxidases, malondialdehyde (MDA) content and changes in coelomocytes were investigated in earthworms (Eisenia andrei) exposed to different concentrations of aluminium chloride (range 0–200 mg Al kg⁻¹ dry soil) in artificial soils for 32 days. Within the first 16 days of Al exposure, catalase activity was elevated in most treatments, while the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) were inhibited in all treatments. After 16 days exposure, SOD and GSH-Px activities returned to normal at lower Al concentrations, but were still inhibited at higher concentrations, hence the inhibition of SOD and GSH-Px showed some exposure-level dependence during the late exposure phase. MDA content was significantly elevated from 16 days after initial exposure. Neutral Red retention time of coelomocytes decreased at the highest exposure concentrations after 32 days, and an increased proportion of cells showing membrane damage was also observed at this time using flow cytometry. We conclude that excessive Al in soils can cause oxidative stress and cell damage in earthworms. Hence, Al accumulation in the environment may present an ecological hazard through suppression of the important functions of earthworms in soil ecosystems.

Keywords:

• aluminium
• earthworm
• antioxidase
• MDA
• Neutral Red retention time (NRRT)
• flow cytometry

Acknowledgements

This research was supported by National Natural Science Foundation of China (41071170, 31172360), CNRS-NSFC collaborative project (41111130195), and National Science and Technology Pillar Program during the 11th Five-year Plan of China (2009BAC62B0407). We thank Associate Professor Cory Matthew from Massey University and Dr Jo Cavanagh from Landcare Research of New Zealand for assistance with improving the English expression of the manuscript. Education New Zealand and Ministry of Education of China supported the academic exchange costs for the New Zealand researchers. Finally, we thank the reviewers for their constructive comments that also improved the manuscript.