Impact of progressively cumulative exposure of AgNPs on earthworms (Eisenia fetida) and implication for eco-toxicological risk assessment

Novel Insights into Stereoselective Reproductive Toxicity Induced by Mefentrifluconazole in Earthworms (Eisenia fetida): First Report of Estrogenic Effects

Widespread use of the new chiral triazole fungicide mefentrifluconazole (MFZ) poses a threat to soil organisms. Although triazole fungicides have been reported to induce reproductive disorders in vertebrates, significant research gaps remain regarding their impact on the reproductive health of soil invertebrates. Here, reproduction-related toxicity end points were explored in earthworms (Eisenia fetida) after exposure for 28 d to soil containing 4 mg/kg racemic MFZ, R-(-)-MFZ, and S-(+)-MFZ. The S-(+)-MFZ treatment resulted in a more pronounced reduction in the number of cocoons and juveniles compared to R-(-)-MFZ treatment, and the expression of annetocin gene was significantly downregulated following exposure to both enantiomers. This reproductive toxicity has been attributed to the disruption of ovarian steroidogenesis at the transcriptional level. Further studies revealed that MFZ enantiomers were able to activate the estrogen receptor (ER). Indirect evidence for this estrogenic effect is provided by the introduction of 17β-estradiol, which also induces reproductive disorders through ER activation.

Toxicological analysis of Eisenia fetida in soil under the coexistence of rockwool substrate andtricyclazole

This study investigated the combined effects of rockwool, a novel seedling substrate, and tricyclazole (TCA) on the bioavailability of TCA to Eisenia fetida. The single addition of rockwool and TCA alone to the soil inhibited the growth of E. fetida. A high concentration (300 mg·L-1) of TCA significantly decreased the biomass of E. fetida. The addition of 20-mesh rockwool reduced this effect on earthworm biomass by decreasing the soil TCA through adsorption, effectively mitigating TCA bioaccumulation in earthworms. A mechanistic analysis showed that the Mg-O functional group on the rockwool surface combined with the CC functional group in TCA to generate Mg-O-C, and the adsorption process was dominated by chemisorption. Toxicology experiments demonstrated that malondialdehyde and cellulase could be used as biomarkers of inhibitory effects of combined rockwool and TCA in soil on E. fetida. Macrogenomic analyses revealed that small particle sizes and high concentrations of rockwool caused co-stress effects on earthworms when TCA was present. When the particle size of rockwool increased, the toxic effect of TCA on earthworms instead decreased at higher rockwool concentrations. Therefore, in practical agricultural production, the particle size of rockwool can be controlled to realize the adsorption of TCA and reduce the toxic effects of TCA and rockwool on earthworms.

Metabolomics and microbiomics revealed the combined effects of different-sized polystyrene microplastics and imidacloprid on earthworm intestinal health and function

The coexistence of pesticides and plastic film residues in agricultural soils poses a significant threat to soil organisms due to their potential long-term contamination and combined toxic effects. Specifically, earthworms are at risk of simultaneously ingesting residual pesticides and microplastics, yet the impact of this combined exposure on their intestinal health and function remains poorly understood. In this study, earthworm (Eisenia fetida) were single and combined exposed to three particle sizes (10 μm, 500 μm, and 2 mm) of polyethylene microplastics (PE MPs) and imidacloprid (IMI) for 28 days, respectively. Our findings underscore that compared to single exposures, the combined exposure inflicted more profound injuries on intestinal tissues and elicited a heightened activation of intestinal digestive enzymes. Furthermore, the combined exposure significantly perturbed the relative abundance of several pivotal metabolic-associated gut microbiota, fostering an enrichment of pathogenic species. Metabolomics analysis showed combined exposure increased differential metabolites, disrupting amino acid, fatty acid, and carbohydrate metabolism in earthworm intestines, potentially hindering nutrient absorption and causing toxic metabolite accumulation. An integrated omics analysis implies that combined exposures have the potential to disrupt the relative abundance of crucial gut microbiota in earthworms, thereby altering their intestinal metabolism and subsequently impacting intestinal health and functionality. Overall, the results reveal that combined exposure of IMI and PE MPs exacerbate the negative effects on earthworm gut health, and this study holds significant implications for the holistic understanding of the combined toxic effects of microplastics and pesticide on soil ecosystems.

Assessment of toxic effects of thallium on the earthworm Eisenia fetida using the biomarker response index

Thallium (Tl), though not essential for biological systems, is widely used in industrial activities, resulting in soil pollution and adverse effects on soil biota. Systematic toxicological studies on Tl, especially concerning soil organisms, are relatively rare. This research evaluates the toxic effects of Tl on earthworms by measuring oxidative stress biomarkers, such as superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), malondialdehyde (MDA), and 8-hydroxydeoxyguanosine (8-OHdG), and by assessing the expression of functional genes, such as heat shock protein 70 (Hsp70), metallothionein (MT), and annetocin (ANN). Additionally, this study employs the Biomarker Response Index (BRI) and two-way ANOVA to comprehensively assess the cumulative toxicity of Tl in earthworms. The findings indicate that Tl exposure significantly exacerbates oxidative stress and cellular damage in earthworms, particularly under conditions of high concentration and prolonged exposure. BRI results demonstrate a continuous decline in the physiological state of earthworms with increasing Tl concentration and exposure duration. Two-way ANOVA reveals significant dose-responsive increases in SOD and CAT activities, as well as in ANN gene expression. Apart from GST activity, other biomarkers significantly increased over time, and the changes in biomarkers such as SOD, CAT, MDA, and 8-OHdG were significantly influenced by dose and time. LSD post hoc tests show significant effects of dose, time, and their interactions on all biomarkers except for GST. These findings are valuable for gaining a deeper understanding of the ecological risks of Tl in soil environments and its potential threats to soil biota, aiding in the management of ecological risks associated with Tl-contaminated soils.

Multilevel investigation of the ecotoxicological effects of sewage sludge biochar on the earthworm Eisenia fetida

The ecological risks of sewage sludge biochar (SSB) after land use is still not truly reflected. Herein, the ecological risks of SSB prepared at different temperature were investigated using the earthworm E. fetida as a model organism from the perspectives of organismal, tissue, cellular, and molecular level. The findings revealed that the ecological risk associated with low-temperature SSB (SSB300) was more pronounced compared to medium- and high-temperature SSB (SSB500 and SSB700), and the ecological risk intensified with increasing SSB addition rates, as revealed by an increase in the integrated biomarker response v2 (IBRv2) value by 2.59-25.41 compared to those of SSB500 and SSB700. Among them, 10% SSB300 application caused significant oxidative stress and neurotoxicity in earthworms compared to CK (p < 0.001). The weight growth rate and cocoon production rate of earthworms were observed to decrease by 25.06% and 69.29%, respectively, while the mortality rate exhibited a significant increase of 33.34% following a 10% SSB300 application, as compared to the CK. Moreover, 10% SSB300 application also resulted in extensive stratum corneum injury and significant longitudinal muscle damage in earthworms, while also inducing severe collapse of intestinal epithelial cells and disruption of intestinal integrity. In addition, 10% SSB300 caused abnormal expression of earthworm detoxification and cocoon production genes (p < 0.001). These results may improve our understanding of the ecotoxicity of biochar, especially in the long term application, and contribute to providing the guidelines for applying biochar as a soil amendment.

Speciation, bioaccumulation, and toxicity of the newly deposited atmospheric heavy metals in soil-earthworm (Eisenia fetida) system near a large copper smelter

The speciation, bioaccumulation, and toxicity of the newly deposited atmospheric heavy metals in the soil-earthworm (Eisenia fetida) system were investigated by a fully factorial atmospheric exposure experiment using soils exposed to 0.8-year and 1.8-year atmospheric depositions. The results shown that the newly deposited metals (Cu, Cd, and Pb) primarily accumulated in the topsoil (0-6 cm) and were present as the highly bioavailable speciation. They can migrate further to increase the concentrations of Cu, Cd, and Pb in soil solution of the deeper layer (at 10 cm) by 12 %-436 %. Earthworms tended to preferentially accumulate the newly deposited metals, which contributed 10 %-61 % of Cu, Cd, and Pb in earthworms. Further, for the unpolluted and moderately polluted soils, the newly deposited metals induced the significant oxidative stress in earthworms, resulting in significant increases in antioxidant enzyme activities (SOD, CAT, and GSH-Px). No significant differences were observed in the levels of heavy metals in soil solutions, bioaccumulation, and enzyme activities in earthworms exposed to 0.8-year and 1.8-year depositions, indicating the bioavailability of atmospheric metals deposited into soils was rapidly decreased with time. This study highlights the high bioaccumulation and toxicity of heavy metals to earthworm from the new atmospheric deposition during the earthworm growing period.

Polyethylene mulch film-derived microplastics enhance the bioaccumulation of atrazine in two earthworm species (Eisenia fetida and Metaphire guillelmi) via carrier effects

Microplastics (MPs) may significantly affect the bioavailability of coexisting pollutants in soil by adsorption-desorption behavior. However, the mechanisms underlying these interaction remain unclear. Herein, the influence of unused polythylene mulch film-derived MPs (MFMPs) and farmland residual polyethylene mulch film-derived MPs (MFMPs-aged) on the adsorption-desorption behavior and bioavailability of atrazine (ATZ) in soil were investigated. The adsorption kinetics and the adsorption isotherms of ATZ on soil, MFMPs, and MFMPs-aged fitted well by the pseudo-second-order model and the Langmuir model, respectively. ATZ were easier to desorb from soil, MFMPs, and MFMPs-aged in the simulated earthworm digestive fluid than that in the CaCl₂ solution. The adsorption and desorption capacities of MFMPs and MFMPs-aged for ATZ were higher than those of soil, especially for MFMPs-aged. The existence of MPs in soil strengthened the adsorption and desorption capacities of ATZ, and the strengthened effects were promoted by the addition amount and aging process of MPs. Moreover, the occurrence of MPs significantly increased the bioaccumulation of ATZ in earthworms, especially for MFMPs-aged. This study deepens the knowledge of the interaction mechanisms of mulch film-derived MPs and pesticide pollution.