Using the Nematode Caenorhabditis elegans daf-16 Mutant to Assess the Lifespan Toxicity of Prolonged Exposure to Ecotoxic Agents

Nematodes are highly abundant organisms found in soil or sedimentary habitats. The free-living nematode Caenorhabditis elegans (C. elegans) has been used as an excellent model for monitoring ecotoxicity in soil. We have previously demonstrated that the lifespan of C. elegans can be used as an endpoint for detecting the ecotoxicity of heavy metals and detergents, and have developed a novel ecotoxicity assay based on their shortened lifespan. Herein we used a daf-16(mu86) mutant CF1038 strain, which has a deficient transcription factor DAF-16 regulating a variety of genes involved in longevity and stress response, for ecotoxicity assays. We carefully examined the effects on reproduction, larval growth, and lifespan in the short-lived CF1038 strain and wild-type N2 strain in the presence of a perfluoro organic compound (pentadecafluorooctanoic acid) and an organophosphate insecticide (dichlorvos) in addition to heavy metals (CuSO4 and CdCl2) and detergents (sodium dodecyl sulfate and a commercially available household detergent). Unexpectedly, both strains exhibited comparable reductions in these endpoints including lifespan by exposure to these ecotoxicants, indicating that DAF-16 does not largely contribute to tolerance to these agents. By virtue of a shorter assay period, the lifespan-based assay using the daf-16 mutant can be useful for assessing the ecotoxicity of a variety of ecotoxic chemicals.