Exploiting the unique phenotypes of the earthworm Eudrilus eugeniae to evaluate the toxicity of chemical substances.

Both the evaluation and the determination of toxicity of chemical substances present in the environment have implications in human health. In this present study, the natural phenomenon named autotomy, a self-defense mechanism employed by several animals against the toxic chemical contaminants, was considered to assess the toxicity of different chemical substances. We investigated the effects of glucose, sodium chloride, kanamycin, mercuric chloride, arsenic trioxide, and lead oxide on the phenotypes of earthworm Eudrilus eugeniae. Depending on the concentration of different chemicals, worms exhibit unique phenotypes. These phenotypes can be used to identify the toxicity as well as the toxic concentration of the chemicals. Upon exposure to toxic chemicals, worms use different mechanical forces at the site of cleavage furrow to detach its segments. During the detachment, there is no apparent blood loss at both the ends of the worm. Our results show that the mercuric chloride is toxic at the concentration above 5 μg when compared to other chemicals. Based on our findings, the toxic effects of a chemical and the toxic concentration of a chemical can be evaluated in both cost and time-efficient manner; in addition, these chemicals can be classified into the following categories: (1) mercuric chloride is extreme-toxic, (2) arsenic trioxide and lead oxide is toxic, (3) kanamycin and sodium chloride is low-toxic, and (4) glucose is non-toxic.