Sewage sludge contains Ag₂S-NPs causing NP exposure of soil fauna when sludge is applied as soil amendment. Earthworm bioturbation is an important process affecting many soil functions. Bioturbation may be affected by the presence of Ag₂S-NPs, but the earthworm activity itself may also influence the displacement of these NPs that otherwise show little transport in the soil. The aim of this study was to determine effects of Ag₂S-NPs on earthworm bioturbation and effect of this bioturbation on the vertical distribution of Ag₂S-NPs. Columns (12 cm) of a sandy loamy soil with and without Lumbricus rubellus were prepared with and without 10 mg Ag kg⁻¹, applied as Ag₂S-NPs in the top 2 cm of the soil, while artificial rainwater was applied at ∼1.2 mm day⁻¹. The soil columns were sampled at three depths weekly for 28 days and leachate collected from the bottom. Total Ag measurements showed more displacement of Ag to deeper soil layers in the columns with earthworms. The application of rain only did not significantly affect Ag transport in the soil. No Ag was detected in column leachates. X-ray tomography showed that changes in macro porosity and pore size distribution as a result of bioturbation were not different between columns with and without Ag₂S-NPs. Earthworm activity was therefore not affected by Ag₂S-NPs at the used exposure concentration. Ag concentrations along the columns and the earthworm density allowed the calculation of the bioturbation rate. The effect on the Ag transport in the soil shows that earthworm burrowing activity is a relevant process that must be taken into account when studying the fate of nanoparticles in soils.

The aim of this study was to estimate the bioavailability of essential (Zn, Cu) and non-essential metals (Cd, Pb) to the earthworm Lumbricus rubellus exposed to soils originating from a gradient of metal pollution in Southern Poland. Metal uptake and elimination kinetics were determined and related to soils properties. Experimental results were compared with tissue metal concentrations observed in earthworms from the studied transect. Cd and Pb were intensively accumulated by the earthworms, with very slow or no elimination. Their uptake rate constants, based on 0.01 M CaCl2-extractable concentrations in the soils, increased with soil pH. Internal concentrations of Cu and Zn were maintained by the earthworms at a stable level, suggesting efficient regulation of these metals by the animals. The estimated uptake and elimination kinetics parameters enabled fairly accurate prediction of metal concentrations reached within a life span of L. rubellus in nature.

The earthworm Lumbricus rubellus (Hoffmeister, 1843) is a terrestrial pollution sentinel. Enzyme activity and transcription of phase II detoxification superfamily glutathione transferases (GST) is known to respond in earthworms after soil toxin exposure, suggesting GST as a candidate molecular-based pollution biomarker. This study combined sub-proteomics, bioinformatics and biochemical assay to characterise the L. rubellus GST complement as pre-requisite to initialise assessment of the applicability of GST as a biomarker. L. rubellus possesses a range of GSTs related to known classes, with evidence of tissue-specific synthesis. Two affinity-purified GSTs dominating GST protein synthesis (Sigma and Pi class) were cloned, expressed and characterised for enzyme activity with various substrates. Electrospray ionisation mass spectrometry (ESI-MS) and tandem mass spectrometry (MS/MS) following SDS-PAGE were superior in retaining subunit stability relative to two-dimensional gel electrophoresis (2-DE). This study provides greater understanding of Phase II detoxification GST superfamily status of an important environmental pollution sentinel organism. This study currently provides the most comprehensive view of the Phase II detoxification enzyme superfamily of glutathione transferases within the important environmental pollution sentinel earthworm Lumbricus rubellus.

Massive use of pesticides in conventional agriculture leads to accumulation in soil of complex mixtures, triggering questions about their potential ecotoxicological risk. This study assessed cropland soils containing pesticide mixtures sampled from conventional and organic farming systems at La Cage and Mons, France. The conventional agricultural field soils contained more pesticide residues (11 and 17 versus 3 and 11, respectively) and at higher concentrations than soils from organic fields (mean 6.6 and 10.5 versus 0.2 and 0.6 μg kg⁻¹, respectively), including systemic insecticides belonging to neonicotinoids, carbamate herbicides and broad-spectrum fungicides mostly from the azole family. A risk quotient (RQᵢ) approach evaluated the toxicity of the pesticide mixtures in soil, assuming concentration addition. Based on measured concentrations, both conventional agricultural soils posed high risks to soil invertebrates, especially due to the presence of epoxiconazole and imidacloprid, whereas soils under organic farming showed negligible to medium risk. To confirm the outcome of the risk assessment, toxicity of the soils was determined in bioassays following standardized test guidelines with seven representative non-target invertebrates: earthworms (Eisenia andrei, Lumbricus rubellus, Aporrectodea caliginosa), enchytraeids (Enchytraeus crypticus), Collembola (Folsomia candida), oribatid mites (Oppia nitens), and snails (Cantareus aspersus). Collembola and enchytraeid survival and reproduction and land snail growth were significantly lower in soils from conventional compared to organic agriculture. The earthworms displayed different responses: L. rubellus showed higher mortality on soils from conventional agriculture and large body mass loss in all field soils, E. andrei showed considerable mass loss and strongly reduced reproduction, and A. caliginosa showed significantly reduced acetylcholinesterase activity in soils from conventional agriculture. The oribatid mites did not show consistent differences between organic and conventional farming soils. These results highlight that conventional agricultural practices pose a high risk for soil invertebrates and may threaten soil functionality, likely due to additive or synergistic “cocktail effects”.

Physicochemical properties of nanoparticles influence their environmental fate and toxicity, and studies investigating this are vital for a holistic approach towards a comprehensive and adequate environmental risk assessment. In this study, we investigated the effects of size, surface coating (charge) of silver nanoparticles (AgNPs) – a most commonly-used nanoparticle-type, on the bioaccumulation in, and toxicity (survival, growth, cocoon production) to the earthworm Lumbricus rubellus. AgNPs were synthesized in three sizes: 20, 35 and 50 nm. Surface-coating with bovine serum albumin (AgNP_BSA), chitosan (AgNP_Chit), or polyvinylpyrrolidone (AgNP_PVP) produced negative, positive and neutral particles respectively. In a 28-day sub-chronic reproduction toxicity test, earthworms were exposed to these AgNPs in soil (0–250 mg Ag/kg soil DW). Earthworms were also exposed to AgNO3 at concentrations below known EC50. Total Ag tissue concentration indicated uptake by earthworms was generally highest for the AgNP_BSA especially at the lower exposure concentration ranges, and seems to reach a plateau level between 50 and 100 mg Ag/kg soil DW. Reproduction was impaired at high concentrations of all AgNPs tested, with AgNP_BSA particles being the most toxic. The EC50 for the 20 nm AgNP_BSA was 66.8 mg Ag/kg soil, with exposure to <60 mg Ag/kg soil already showing a decrease in the cocoon production. Thus, based on reproductive toxicity, the particles ranked: AgNP_BSA (negative) > AgNP_PVP (neutral) > Chitosan (positive). Size had an influence on uptake and toxicity of the AgNP_PVP, but not for AgNP_BSA nor AgNP_Chit. This study provides essential information on the role of physicochemical properties of AgNPs in influencing uptake by a terrestrial organism L. rubellus under environmentally relevant conditions. It also provides evidence of the influence of surface coating (charge) and the limited effect of size in the range of 20–50 nm, in driving uptake and toxicity of the AgNPs tested.

Using synchrotron- and electron microscope-based X-ray microanalyses, the distribution and speciation of Zn and Pb were examined in situ in two earthworm species (Dendrodrilus rubidus and Lumbricus rubellus) living in heavily-polluted soils. Main findings: (i) Zn spectra in ingested soil and in tissues more closely resembled Zn3(PO4)2 than ZnS; (ii) Zn speciation in tissues gave a best fit for Zn to the inner shell of 4 oxygens at 1.94 Å (or nitrogens at 1.96 Å); (iii) the best fit for Pb in tissue was with a shell of oxygens at 2.18 Å and a shell of sulphurs at 2.67 Å; (iv) a component of the Zn and much of the Pb detectable in gut contents was co-distributed with S; (v) Zn and Pb display ‘soft’ acid affinities in soil, but ‘hard’ acid affinities in tissue. This is the first metal characterisation study conducted on an invertebrate quench-frozen in the field.

Effects of C₆₀ nanoparticles (nominal concentrations 0, 15.4 and 154mg/kg soil) on mortality, growth and reproduction of Lumbricus rubellus earthworms were assessed. C₆₀ exposure had a significant effect on cocoon production, juvenile growth rate and mortality. These endpoints were used to model effects on the population level. This demonstrated reduced population growth rate with increasing C₆₀ concentrations. Furthermore, a shift in stage structure was shown for C₆₀ exposed populations, i.e. a larger proportion of juveniles. This result implies that the lower juvenile growth rate due to exposure to C₆₀ resulted in a larger proportion of juveniles, despite increased mortality among juveniles. Overall, this study indicates that C₆₀ exposure may seriously affect earthworm populations. Furthermore, it was demonstrated that juveniles were more sensitive to C₆₀ exposure than adults.

The scale of variation in species sensitivity to toxicants has been theoretically linked to mode of action. Specifically, it has been proposed there will be greater variations for chemicals with a putative specific biological target than for toxicants with a non-specific narcotic mechanism. Here we test the hypothesis that mode of action is related to variation in sensitivity in a specifically designed experiment for species from a single ecologically important terrestrial taxa, namely earthworms. Earthworm toxicity tests were conducted with five species for four chemicals, providing a series of increasingly complex modes of action: a putative narcotic polycyclic aromatic hydrocarbon (fluoranthene), and three insecticides (chlorpyrifos, cypermethrin, imidacloprid) with known neuronal receptor targets. Across all the chemicals, the standard epigeic test species Eisenia fetida and Lumbricus rubellus, were generally among the two least sensitive, while the endogenic Aporrectodea caliginosa and Megascolecidae Amynthas gracilis were generally more sensitive (never being among the two least sensitive species). This indicates a potential for bias in the earthworm ecotoxicology literature, which is dominated by studies in epigeic Lumbricidae, but contains few endogeic or Megascolecidae data. Results confirmed the lowest range of variation in sensitivities for effects on reproduction was for fluoranthene (2.5 fold). All insecticides showed greater variation for species sensitivity (cypermethrin: 7.5 fold, chlorpyrifos: 10.3 fold, imidacloprid: 31.5 fold) consistent with the specific mechanisms of the pesticides. Difference in toxicodynamics, based on mode of action specificity and receptor complexity was reflected in the magnitude of sensitivity variation. However, measurements of tissue concentrations also indicated the potential importance of toxicokinetics in explaining species sensitivity variations for chlorpyrifos and cypermethrin.

Exposures of Lumbricus rubellus to a series of arsenic concentrations in soil were used to assess life-stage (juvenile, adult) and genotype specific sensitivities, to calculate population growth rate (λ) and to assess patterns of As accumulation. Significant mortality was seen in juveniles at 125 mg/kg As, while growth and maturation was affected from 36 mg/kg and above. In adults, cocoon production at the highest concentration (125 mg/kg) was significantly reduced. Phylogenetic analysis was performed by comparison of mitochondrial sequences to establish genotypic variation among juveniles. Three clades with more than 7.5% divergent were described, with 70% of earthworms belonging to a single clade. Date of and mass at maturation was significantly different between clades, but clades were not differentially As sensitive. Parameter λ was reduced at 36 mg/kg As and was negative at 125 mg/kg As, suggesting impacts and population stability and potential extinction at environmentally relevant concentrations.

A Pb-mine site situated on acidic soil, but comprising of Ca-enriched islands around derelict buildings was used to study the spatial pattern of genetic diversity in Lumbricus rubellus. Two distinct genetic lineages (‘A’ and ‘B’), differentiated at both the mitochondrial (mtDNA COII) and nuclear level (AFLPs) were revealed with a mean inter-lineage mtDNA sequence divergence of approximately 13%, indicative of a cryptic species complex. AFLP analysis indicates that lineage A individuals within one central ‘ecological island’ site are uniquely clustered, with little genetic overlap with lineage A individuals at the two peripheral sites. FTIR microspectroscopy of Pb-sequestering chloragocytes revealed different phosphate profiles in residents of adjacent acidic and calcareous islands. Bioinformatics found over-representation of Ca pathway genes in ESTPb libraries. Subsequent sequencing of a Ca-transport gene, SERCA, revealed mutations in the protein's cytosolic domain. We recommend the mandatory genotyping of all individuals prior to field-based ecotoxicological assays, particularly those using discriminating genomic technologies. Landscapes punctuated by Pb-polluted islands have engendered local genetic differentiation in resident earthworms.