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Defense responses in earthworms (Eisenia fetida) exposed to low-density polyethylene microplastics in soils
Summary
Researchers exposed earthworms to low-density polyethylene microplastics in soil at various concentrations for 28 days. They found that the earthworms ingested microplastics in a dose-dependent manner and actually broke some particles into smaller pieces during digestion, with about 30% more particles under 100 micrometers found in their excrement compared to the original soil. At higher concentrations, the microplastics triggered oxidative stress and neurotoxic responses, suggesting potential ecological risks to soil organisms.
The potential threats of microplastics to global health are a new problem. However, little is known about the influence of microplastics on soil organisms. Here, we investigated the effects of low-density polyethylene (LDPE, < 400 μm) on earthworms (Eisenia fetida) under different concentrations (0.1, 0.25, 0.5, 1.0, 1.5 g/kg dry) with three replicates in artificial soil. Results showed that surface damage of earthworms was observed at the concentration of 1.5 g/kg LDPE after exposure 28 days. The microplastics were ingested in a dose-response manner. Smaller sizes of LDPE microplastics were found in the casts of E. fetida, and approximately 30% of the microplastics egested (size < 100 μm) were increased compared with initial microplastics in the soil. The catalase activity and malondialdehyde content increased significantly at the concentration of 1.0 g/kg LDPE after exposure 28 days, and acetylcholine esterase was significantly stimulated at concentrations of 1.5 and 1.0 g/kg LDPE on days 21 and 28, respectively. The results of this study demonstrate the potential risk of LDPE microplastics to E. fetida and may provide a reference for the impact of microplastics on terrestrial creatures.