Chapter 3. Aporrectodea longa (Annelida, Lumbricidae): A Suitable Earthworm Model for Genotoxicity Evaluation in the Environment

Abstract

There remains a need for systems that can accurately predict the genotoxicity potential of real-world environmental contexts accurately and in a high-throughput, low-cost fashion. Aporrectodea longa is an abundant species of earthworm that could be adapted as a sentinel organism to investigate spatial and temporal exposure effects. We amended soil samples with 12C-labelled compounds [benzo[a]pyrene (B[a]P) as positive control, cypermethrin, diazinon or isoproturon) at levels in line with real-world typical environmental levels. These were placed in glass jars, whereupon A. longa were exposed for 24 h. Soil samples amended with cypermethrin were variously aged up to 100 days. Post-exposure, coelomic fluid containing coelomyocytes were harvested and incorporated into the alkaline single cell-gel electrophoresis (‘comet’) assay. In isolated nuclei, DNA damage in the form of single-strand breaks (SSBs) was quantified as Comet tail length (CTL, μm). Significant (P <0.0001) Comet-forming activity was identified with all test agents; however, ageing appeared to reduce the potential for cypermethrin-induced comet formation. Amendment of soil samples with 14C-labelled compounds allowed organism uptake to be quantified. This showed that A. longa ingests or dermally absorbs such environmental contaminants in soil and can be employed as a sensitive indicator of environmental contaminants. Coelomyocytes are readily harvested from these earthworms in a non-sacrificial manner, can be incorporated into short-term genotocicity assays to detect DNA SSBs and can allow for spatial and/or temporal studies. This has great potential for identifying environmental contamination especially for use in monitoring of land remediation.