Abstract: To study the damage of Cu²⁺ to acclimated earthworms, Eisenia fetida was acclimated under the exposure to a nonlethal concentration of copper (100 mg Cu²⁺·kg^-1) for two weeks, with the un-acclimated E. fetida as the control. The acute toxicity of Cu²⁺ to the acclimated and un-acclimated E. fetida was determined, and the DNA damage of acclimated E. fetida under Cu²⁺ stress (400 mg·kg^-1) was detected by comet assay. On day 14, the 50% lethal concentration (LC₅₀) of Cu²⁺ for acclimated and un-acclimated E. fetida was 321.83-542.45 and 230.83-342.91mg·kg^-1, respectively, and the survival rate of acclimated E. fetida increased significantly. The comet assay showed that the tail length, tail DNA content, and tail moment of the earthworms were in non-normal distribution. On day 11 and day 14, the damaged level of DNA in acclimated E. fetida was much lower than that in unacclimated E. fetida. The results indicated that comet assay was an effective way to detect the gene damage of living E. fetida under copper stress, and the DNA damage of E. fetida could be used as a biomarker to indicate the impacts of heavy metals pollutants.

Key words: macrobenthos, community characteristics, biodiversity, ABC curves, ANOSIM analysis.