Multi-generation toxicity of zinc, cadmium, copper and lead to the potworm Enchytraeus albidus

Multigenerational and transgenerational effects of azoxystrobin on Folsomia candida

Soil organisms are exposed to various pollutants during several generations. However standard toxicity tests are often based on exposure in only one generation. Research of multigenerational (MG) and transgenerational (TG) effects are still quite scarce, however evidence accumulates that effects observed in one generation can be significantly different in some of the following generations, with different effects observed. Some studies suggest adaptation to pollutants, while others report severe effects in following generations. Azoxystrobin is commonly used in the prevention and treatment of fungal diseases in a wide range of economically important crops. The main aim of this study was to assess the toxic effects of azoxystrobin (AZO) on F. candida over 3 generations through the application of biochemical and population level biomarkers. Results of reproduction tests showed a significant decrease in estimated EC50 values, with EC50 for F0 being estimated at 104.44 mga.i./kgD.W.soil and only 15.4 mga.i./kgD.W.soil for F1. In F1 a significant reduction in the number of juveniles was observed, and at AZO concentration of 50 mga.i./kgD.W and higher, F1 did not reproduce. Significant oxidative stress was observed in all generations, with increased SOD and lipid damage that slowly decreased in subsequent generations. Transgenerational effects were also observed, with a significantly reduced number of juveniles in F1 and significant oxidative stress and lipid damage in all generations. IBRv2 showed that F1 was most affected, followed by F0, and least affected was F3. When considering the whole body energy budget, F1 to F3 had significantly higher WBEB compared to F0, and a shift in proportion of energy reserves occurred in F1, where the proportion of lipids increased while protein decreased. Results of this research show that considering standard toxicity tests, risks for populations of soil organisms are possibly severely underestimated. Therefore, standard toxicity guidelines should be supplemented by multigenerational tests, when possible.

On the importance of longer-term exposure to stressors - A critical review and proposal for multigenerational testing in standard soil invertebrates

Standard laboratory tests to describe the impact of stressors (most notably: chemicals) on organisms offer a good compromise between feasibility and outcome, i.e., they should be reproducible and provide robust results. However, these tests may underestimate the potential effects of prolonged exposures, particularly for persistent contaminants. Within the last years, we have observed an increase in studies aiming to target prolonged exposure, e.g., via an extended test duration or by multigenerational (MG) exposure. Seemingly, both reduced and increased impacts have been observed in these studies, but it is also clear that no unique test setup was used, and test designs vary widely among studies. To better describe long term effects, MG is a highly relevant aspect which deserves more consideration at various testing and assessment levels. Therefore, we conducted a literature review focusing on available studies performed with soil invertebrates, exposed to stressors for periods longer than in standard laboratory tests, i.e., full life cycle tests, as well as extensions to standard and MG tests. So far, it has been recommended that such studies should cover more than one generation, but this statement is probably too vague. In this contribution, we summarize and critically discuss the information provided in the literature, and we provide suggestions for future research. The currently available test results from long-term studies have produced clear evidence to recommend the implementation of long-term tests in existing regulatory testing requirements (e.g., for pesticides), in particular for persistent substances and also for delayed effects. Consequently, we recommend the inclusion of such longer exposure test designs (e.g., as annexes) in current OECD and ISO guidelines. However, when doing so, the long-term test designs proposed so far have to be critically adapted for a selected set of representative soil invertebrate test species.

Response addition is more protective of biogeochemical cycles of carbon and phosphorus compared to concentration addition

In soils, enzymes are crucial to catalyzing reactions and cycling elements such as carbon (C), nitrogen (N), and phosphorus (P). Although these soil enzymes are sensitive to metals, they are often disregarded in risk assessments, and regulatory laws governing their existence are unclear. Nevertheless, there is a need to develop regulatory standards for metal mixtures that protect biogeochemical cycles because soil serve as a sink for metals and exposures occur as mixtures. Using a fixed ratio ray design, we investigated the effects of 5 single metals and 10 quinary mixtures of Zn, Cu, Ni, Pb, and Co metal oxides on two soil enzymes (i.e., acid phosphatases [ACP] and beta glucosidases [BGD]) in two acidic Canadian soils (S1: acid sandy forest soil, and S2: acid sandy arable soil), closely matched to EU REACH standard soils. Compared to BGD, ACP was generally the more sensitive enzyme to both the single metals and the metal mixtures. The effective concentration inhibiting 50% enzyme activity (EC₅₀) estimates for single Cu (2.1-160.7 mmol kg^-1) and Ni (12-272 mmol kg^-1) showed that those were the most toxic to both enzymes in both soils. For metal mixtures, response addition (RA) was more conservative in predicting metal effects compared to concentration addition (CA). For both additivity models, antagonism was observed except at lower concentrations (≤10,000 mg/kg) where synergism was observed. At higher concentrations (>10,000 mg/kg), free and CaCl₂ extractable Cu protected both enzymes against the toxicity of other metals in the mixture. The results suggest that assuming CA at concentrations less than EC₅₀ does not protect biogeochemical cycling of C and P. And Cu in soil may protect soil enzymes from other toxic metals and thus may have an overall positive role.

Evidence for the metal resistance of earthworm Eisenia fetida across generations (F1 and F2) under laboratory metal exposure

Environmental stressors are persistent but most toxicological studies always evaluate the risk via short-term acute toxicity, while continuous toxicity and biological resistance across generations are relatively unknown. Here, earthworm Eisenia fetida was laboratory-reared and exposed to historically contaminated soils with an increasing metal gradient (CK, LM and HM), to investigate cross-generation toxicity and resistance of F1 and F2 worms. The results elucidated that biomass and juvenile hatching rate of F2 E. fetida showed maximum decreases of 20.8% and 38.5% than those of F1, which indicated severer toxicity of earthworm offspring. However, metal bioaccumulation in F2 E. fetida showed maximum increases of 150%, 49.2%, 19.7% and 25.5% than F1 for Cd, Cu, Zn and Pb, respectively. F2 E. fetida suffered less oxidative stress because the activities of superoxide dismutase (SOD), peroxidase (POD), glutathione (GSH), and malondialdehyde (MDA) contents were basically lower than that of F1. Meanwhile, the detoxification genes of metallothionein and heat shock protein 70 in F2 E. fetida showed maximum of 296% and 78.9% up-regulations, respectively, which suggested greater metal resistance of F2 E. fetida. This study confirmed the cross-generation toxicity and resistance of earthworms, which provides novel insights to reveal specific contaminant risks from longer lifecycles. CAPSULE: Earthworms under cross-generation exposure can develop metal resistance despite suffering worse toxicity effects.

Predicting the thresholds of metals with limited toxicity data with invertebrates in standard soils using quantitative ion character-activity relationships (QICAR)

Terrestrial invertebrates are often used as indicator organisms in ecological risk assessments. However, determining the risk of metals to invertebrates is laborious and time-consuming due to the lengthy testing and ethical approval procedures. In this study, a review of the literature was conducted to provide toxicity data for two standard soils (OECD and LUFA 2.2). An attempt was made to establish models for predicting the toxicity of elements to invertebrates using quantitative ion character-activity relationships (QICARs). In OECD soil, the element toxicity of four groups (Enchytraeus albidus mortality and reproduction, Folsomia candida and Eisenia fetida reproduction) showed significant correlations with atomic number, atomic mass and atomic ionization potential (0.852 ≤ R² ≤ 0.989, P < 0.05). For LUFA 2.2 soil, polarization force parameters and boiling point were most significant parameters for toxicity values of F. candida and Enchytraeus crypticus, respectively (0.866 ≤ R² ≤ 0.962, P < 0.05). Finally, QICAR models were established, and LC₅₀ or EC₅₀ of elements were predicted. Then, models were verified using standard and natural soils, and showed that errors between observed and predicted logLC₅₀/EC₅₀ were mostly < 0.5 orders of magnitude. Thus, the developed QICAR models have potential for predicting the toxicity of elements for soils.

Applicability of Enchytraeus bulbosus as a model species in ecotoxicology and risk assessment

Enchytraeus bulbosus is listed in the ISO and OECD standard guidelines as a possible test species of enchytraeid. However, in contrast to other listed species, its applicability in ecotoxicological studies as well as its sensitivity is widely unknown. Therefore, copper, pentachlorophenol(PCP), carbendazim, and chloroacetamide have been investigated by performing two-generation studies with multiple endpoints. Comparable toxicity trends to the existing studies were shown for copper and PCP in the two-generation studies of E. bulbosus. Dose-related abnormal swelling of clitella were found for the first time with PCP and chloroacetamide treatments. Sensitivity comparisons of E. bulbosus to other terrestrial test species were also conducted. E. bulbosus showed high sensitivity, it has comparable sensitivity as other sensitive species of genus Enchytraeus ( E. albidus or E. luxuriosus)to different chemicals, and was more sensitive than E. crypticus and earthworm species ( Eisenia fetida or Eisenia andrei). Combined with the phylogenetic and biological characterization, the results lead to the conclusion that E.bulbosus is a suitable model species in ecotoxicology and the chemical risk assessment (especially in multi-generation) because it has a short generation time, comparatively moderate fecundity, ideal and reasonable sensitivity.

Lead acetate ecotoxicity in tropical soils

Lead acetate (AcPb) is an important raw material used in chemical industries worldwide. The potential toxicity of AcPb is generally attributed to the presence of Pb. However, the effect of AcPb on the environment as a whole is still poorly known. This study aimed to evaluate AcPb toxicity on three standard species of soil invertebrates and two plant species using ecotoxicology tests. Three tropical soils (Oxisol, Inceptisol, and Tropical Artificial Soil (TAS)) were contaminated with different concentrations of AcPb and one dose of K-acetate (positive control). These soils were used in tests with Eisenia andrei (earthworm), Folsomia candida (springtail), Enchytraeus crypticus (enchytraeid), Zea mays (maize), and Phaseolus vulgaris (common bean). Dose-response curves obtained in the laboratory tests were used to estimate the EC₅₀ values for each species. Among invertebrates, the highest sensitivity to AcPb was observed for E. crypticus in the TAS (EC₅₀ = 29.8 mg AcPb kg^-1), whereas for E. andrei and F. candida the highest sensitivity was observed in the Oxisol (EC₅₀ = 141.9 and 1835 mg AcPb kg^-1, respectively). Folsomia candida was the least sensitive invertebrate species to AcPb in all soils. Among plant species, Z. mays was less sensitive (EC₅₀ = 1527.5 mg AcPb kg^-1) than P. vulgaris (EC₅₀ = 560.5 mg AcPb kg^-1) in the Oxisol. The present study evidenced that the toxicity of AcPb should not be attributed uniquely to the presence of Pb, as the treatment containing uniquely Ac provoked the same toxicity as the highest dose of AcPb.

Toxicity assessment of metal mixtures to soil enzymes is influenced by metal dosing method

Metals are present as mixtures in the environment, yet testing such complex mixture poses design and technical challenges. One possible solution is the use of fixed ratios, i.e. rays of increasing metal concentrations. But fixed ratios rays are compromised when soils dosed with metal salts are leached due to metal-soil selectivity rules. Two alternative metal forms, metal oxides and spinel minerals of quinary metal mixtures (Pb, Cu, Co, Ni, Zn), were evaluated for their toxicity to soil microorganisms measured by the activity of ammonia monooxygenases and acid-phosphatases in three soils. Leaching, a required step for salts, had a larger effect on ammonia monooxygenases than metals. Generally, metal salts were the most toxic form, while the spinel minerals were the least toxic form. Two extractants, CaCl2 and DTPA, were evaluated for their ability to link toxicity to metals across all three metal forms. Salt toxicity was closely linked to CaCl2 extractable concentrations but DTPA was the most appropriate for oxides. We strongly recommend combining fixed ratio rays with metal oxides for metal mixture studies, since soil ratios created using oxides were more precise and required less experimental effort compared to salts and spinel minerals. Furthermore, because DTPA and CaCl2 closely tracked the toxicity of more realistic metal forms (i.e. oxides), we recommend that field studies investigating metal mixtures use both DTPA and CaCl2.

The toxicity of different lead salts to Enchytraeus crypticus in relation to bioavailability in soil

The present study aimed to assess the bioavailability and toxicity of lead nitrate and lead chloride to Enchytraeus crypticus in a natural standard soil. Worms were exposed to Pb-spiked soil for 21 d, and survival and reproduction were related to total, 0.01 M CaCl₂ -extractable, and porewater Pb concentrations in the soil and internal concentrations in the surviving animals. The Pb availability for Pb(NO₃ )₂ and PbCl₂ was similar, as confirmed by Langmuir and Freundlich isotherms. The Pb concentrations in surviving worms increased with increasing Pb concentrations in the soil and did not differ for the 2 Pb salts. Lead was toxic to E. crypticus at median lethal concentrations (LC50s) of 543 and 779 mg Pb/kg dry soil and median effect concentrations (EC50s) of 189 and 134 mg Pb/kg dry soil, for Pb(NO₃ )₂ and PbCl₂ , respectively. Mortality of E. crypticus was related to internal Pb concentrations in the worms rather than to total or available Pb concentrations in the soil, whereas reproduction toxicity was better explained from Pb concentrations in 0.01 M CaCl₂ extracts or porewater of the test soil than from total Pb concentrations in the soil or Pb concentrations in the worms. Overall, the bioavailability and toxicity of Pb(NO₃ )₂ and PbCl₂ to E. crypticus in LUFA 2.2 soil did not differ. Environ Toxicol Chem 2017;36:2083-2091. © 2017 SETAC.

Organic wastes as soil amendments - Effects assessment towards soil invertebrates

Using organic wastes, as soil amendments, is an important alternative to landfilling with benefits to soil structure, water retention, soil nutrient and organic matter concentrations. However, this practice should be monitored for its environmental risk due to the frequent presence, of noxious substances to soil organisms. To evaluate the potential of eight organic wastes with different origins, as soil amendments, reproduction tests with four soil invertebrate species (Folsomia candida, Enchytraeus crypticus, Hypoaspis aculeifer, Eisenia fetida) were performed using gradients of soil-waste mixtures. Results obtained demonstrated that contaminant concentrations required by current legislation might not be a protective measure for the soil ecosystem, as they do not properly translate the potential toxicity of wastes to soil invertebrates. Some wastes with contaminant loadings below thresholds showed higher toxicity than wastes with contaminants concentrations above legal limits. Also, test organism reproduction was differently sensitive to the selected wastes, which highlights the need to account for different organism sensitivities and routes of exposure when evaluating the toxicity of such complex mixtures. Finally this study shows that when combining chemical and ecotoxicological data, it is possible to postulate on potential sources of toxicity, contributing to better waste management practices and safer soil organic amendment products.

Influence of climate change on the multi-generation toxicity to Enchytraeus crypticus of soils polluted by metal/metalloid mining wastes

This study aimed at assessing the effects of increased air temperature and reduced soil moisture content on the multi-generation toxicity of a soil polluted by metal/metalloid mining wastes. Enchytraeus crypticus was exposed to dilution series of the polluted soil in Lufa 2.2 soil under different combinations of air temperature (20 °C and 25 °C) and soil moisture content (50% and 30% of the soil water holding capacity, WHC) over three generations standardized on physiological time. Generation time was shorter with increasing air temperature and/or soil moisture content. Adult survival was only affected at 30% WHC (∼30% reduction at the highest percentages of polluted soil). Reproduction decreased with increasing percentage of polluted soil in a dose-related manner and over generations. Toxicity increased at 30% WHC (>50% reduction in EC₅₀ in F0 and F1 generations) and over generations in the treatments at 20 °C (40-60% reduction in EC₅₀ in F2 generation). At 25 °C, toxicity did not change when combined with 30% WHC and only slightly increased with 50% WHC. So, higher air temperature and/or reduced soil moisture content does affect the toxicity of soils polluted by metal/metalloid mining wastes to E. crypticus and this effect may exacerbate over generations.

Does long term low impact stress cause population extinction?

This study assessed and monitored 40 consecutive reproduction tests - multigenerational (MG) - of continuous exposure to Cd (at 2 reproduction Effect Concentrations (EC): EC10 and EC50) using the standard soil invertebrate Folsomia candida, in total 3.5 years of data were collected. Endpoints included survival, reproduction, size and metallothionein (MTc) gene expression. Further, to investigate adaptation to the toxicant, additional standard toxicity experiments were performed with the MG organisms of F₆, F₁₀, F₂₆, F₃₄ and F₄₀ generations of exposure. Exposure to Cd EC10 caused population extinction after one year, whereas populations survived exposure to Cd EC50. Cd induced the up-regulation of the MTc gene, this being higher for the higher Cd concentration, which may have promoted the increased tolerance at the EC50. Moreover, EC10 induced a shift towards organisms of smaller size (positive skew), whereas EC50 induced a shift towards larger size (negative skew). Size distribution shifts could be an effect predictor. Sensitivity increased up to F₁₀, but this was reverted to values similar to F₀ in the next generations. The maximum Cd tolerance limits of F. candida increased for Cd EC50 MG. The consequences for risk assessment are discussed.

Ecotoxicity of arsenic contaminated sludge after mixing with soils and addition into composting and vermicomposting processes

Sludge coming from remediation of groundwater contaminated by industry is usually managed as hazardous waste despite it might be considered for further processing as a source of nutrients. The ecotoxicity of phosphorus rich sludge contaminated with arsenic was evaluated after mixing with soil and cultivation with Sinapis alba, and supplementation into composting and vermicomposting processes. The Enchytraeus crypticus and Folsomia candida reproduction tests and the Lactuca sativa root growth test were used. Invertebrate bioassays reacted sensitively to arsenic presence in soil-sludge mixtures. The root elongation of L. sativa was not sensitive and showed variable results. In general, the relationship between invertebrate tests results and arsenic mobile concentration was indicated in majority endpoints. Nevertheless, significant portion of the results still cannot be satisfactorily explained by As chemistry data. Composted and vermicomposted sludge mixtures showed surprisingly high toxicity on all three tested organisms despite the decrease in arsenic mobility, probably due to toxic metabolites of bacteria and earthworms produced during these processes. The results from the study indicated the inability of chemical methods to predict the effects of complex mixtures on living organisms with respect to ecotoxicity bioassays.

Low temperatures enhance the toxicity of copper and cadmium to Enchytraeus crypticus through different mechanisms

Knowledge about how toxicity changes with temperature is important for determining the extent of safety factors required when extrapolating from standard laboratory conditions to variable field scenarios. In the present study, the authors evaluated the toxicity of Cu and Cd to the potworm Enchytraeus crypticus at 6 temperatures in the range of 11 °C to 25 °C. For both metals, reproductive toxicity decreased approximately 2.5-fold with increasing temperature. This is contrary to what most other studies have found. Measurements of the bioavailable fraction of the metals in the soils and the internal metal concentrations in the worms over time showed that the major cause of change in toxicity with temperature for Cu was the worms' ability to regulate internal concentration at high temperatures. Uptake of Cd increased with time at all temperatures and with higher rates at high temperatures. Hence, the lower toxicity of Cd at high temperatures is proposed to be due to the E. crypticus being more efficient at immobilizing Cd and/or repairing damages at high compared to low temperatures. The present study concludes that no consistent relationship between metal toxicity and temperature across species can be made. The metabolic dependence of the species in terms of regulating metal uptake, excretion, immobilization, damage, and repair processes, will be crucial factors in determining species susceptibility to metals at varying temperatures.

Toxicity of quantum dots and cadmium salt to Caenorhabditis elegans after multigenerational exposure

To fully understand the biological and environmental impacts of nanomaterials requires studies that address both sublethal end points and multigenerational effects. Here, we use a nematode to examine these issues as they relate to exposure to two different types of quantum dots, core (CdSe) and core-shell (CdSe/ZnS), and to compare the effect to those observed after cadmium salt exposures. The strong fluorescence of the core-shell QDs allowed for the direct visualization of the materials in the digestive track within a few hours of exposure. Multiple end points, including both developmental and locomotive, were examined at QD exposures of low (10 mg/L Cd), medium (50 mg/L Cd), and high concentrations (100 mg/L Cd). While the core-shell QDs showed no effect on fitness (lifespan, fertility, growth, and three parameters of motility behavior), the core QDs caused acute effects similar to those found for cadmium salts, suggesting that biological effects may be attributed to cadmium leaching from the more soluble QDs. Over multiple generations, we commonly found that for lower life-cycle exposures to core QDs the parents response was generally a poor predictor of the effects on progeny. At the highest concentrations, however, biological effects found for the first generation were commonly similar in magnitude to those found in future generations.

Direct and indirect effects of metal contamination on soil biota in a Zn-Pb post-mining and smelting area (S Poland)

Effects of metal contamination on soil biota activity were investigated at 43 sites in 5 different habitats (defined by substratum and vegetation type) in a post-mining area. Sites were characterised in terms of soil pH and texture, nutrient status, total and exchangeable metal concentrations, as well as plant species richness and cover, abundances of enchytraeids, nematodes and tardigrades, and microbial respiration and biomass. The concentrations of total trace metals were highest in soils developed on mining waste (metal-rich dolomite), but these habitats were more attractive than sandy sites for plants and soil biota because of their higher content of organic matter, clay and nutrients. Soil mesofauna and microbes were strongly dependent on natural habitat properties. Pollution (exchangeable Zn and Cd) negatively affected only enchytraeid density; due to a positive relationship between enchytraeids and microbes it indirectly reduced microbial activity.

Assessing joint toxicity of chemicals in Enchytraeus albidus (Enchytraeidae) and Porcellionides pruinosus (Isopoda) using avoidance behaviour as an endpoint

Contamination problems are often characterized by complex mixtures of chemicals. There are two conceptual models usually used to evaluate patterns of mixture toxicity: Concentration Addition (CA) and Independent Action (IA). Deviations from these models as synergism, antagonism and dose dependency also occur. In the present study, single and mixture toxicity of atrazine, dimethoate, lindane, zinc and cadmium were tested in Porcellionides pruinosus and Enchytraeus albidus, using avoidance as test parameter. For both species patterns of antagonism were found when exposed to dimethoate and atrazine, synergism for lindane and dimethoate exposures (with the exception of lower doses in the isopod case study) and concentration addition for cadmium and zinc occurred, while the exposure to cadmium and dimethoate showed dissimilar patterns. This study highlights the importance of dose dependencies when testing chemical mixtures and that avoidance tests can also be used to asses the effects of mixture toxicity.

Assessment of structure and function in metal polluted grasslands using Terrestrial Model Ecosystems

Ecosystem effects of metal pollution in field situations are hard to predict, since metals occur often in mixtures and links between structural (organisms) and functional endpoints (ecosystem processes) are not always that clear. In grasslands, both structure and functioning was suspected to be affected by a mixture of copper, lead, and zinc. Therefore, the structural and functional variables were studied simultaneously using Terrestrial Model Ecosystems (TMEs). Comparing averages of low- and high-polluted soil, based on total metal concentrations, did not show differences in structural and functional variables. However, nematode community structure (Maturity Index) negatively correlated with metal concentrations. Next to that, multivariate statistics showed that enchytraeid, earthworm and, to lesser extent, nematode diversity decreased with increasing metal concentrations and a lower pH in the soil. Bacterial CFU and nematode biomass were positively related with decomposer activity and nitrate concentrations. Nitrate concentrations were negatively related to ammonium concentrations. Earthworm biomass, CO(2) production and plant yield were not related to metal concentrations. The most metal-sensitive endpoint was enchytraeid biomass. In all analyses, soil pH was a significant factor, indicating direct effects on organisms, or indicating indirect effects by influencing metal availability. In general, structural diversity seemed more positively related to functional endpoints than structural biomass. TMEs proved valuable tools to assess the structure and function in metal polluted field situations. The outcome feeds modeling effort and direct future research.

Toxicity of selenate and selenite to the potworm Enchytraeus albidus (Annelida: Enchytraeidae): a laboratory test

Little information is available about the toxicity of inorganic selenium forms in soil animals. Therefore, the effects of selenate and selenite on the mortality and reproduction of Enchytraeus albidus were examined in standard laboratory tests with chronic exposure. Total and available amount of selenate and selenite were tested in a calcareous loamy chernozem soil. The LC(50) of selenate was 5.69 (2.7-8.12) mg kg(-1) dry wt. for total Se and 4.74 (2.14-6.98) mg kg(-1) dry wt. for available Se. Selenite LC(50) was as high as 22.5 (19.6-25.7) mg kg(-1) dry wt. for total Se and 8.10 (6.8-9.6) mg kg(-1) dry wt. for available Se. The EC(50) of selenate was 0.41 (0.35-0.48) mg kg(-1) dry wt. for total Se and 0.28 (0.24-0.34) mg kg(-1) dry wt. for available Se. Selenite EC(50) was as high as 7.3 (6.2-8.5) mg kg(-1) dry wt. for total Se and 2.46 (2.05-2.91) mg kg(-1) dry wt. for available Se. The response in reproduction was more sensitive to Se toxicity than the response in mortality. Selenate proved to be more toxic than selenite. Available data show that E. albidus may function as a biological indicator for some inorganic selenium forms in the soil.

Has long-term metal exposure induced changes in life history traits and genetic diversity of the enchytraeid worm Cognettia sphagnetorum (Vejd.)?

We studied whether long-term metal exposure has affected life history traits, population growth patterns and genetic diversity of the asexual enchytraeid worm Cognettia sphagnetorum (Vejd.). Enchytraeids from metal contaminated and uncontaminated forest soil were compared by growing them individually in the laboratory and by following their population development in patchily Cu contaminated microcosms. Genetic differences between the two native populations were studied using allozyme electrophoresis. Individuals from the contaminated site had slower growth rate and they produced fewer fragments of larger size when compared to individuals from the uncontaminated site. In patchily Cu contaminated microcosms, C. sphagnetorum from the contaminated site had a slower population growth rate. Most alleles were shared by the two native populations, but there was greater diversity and more unique genotypes in the population living in the uncontaminated site. Overall, long-term exposure to metals has induced only slight changes in life history properties and clonal diversity of C. sphagnetorum.