Spinosad application in an apple orchard affects both the abundance of the spider Araneus diadematus and its web construction behaviour.

The principles of organic production are based on the respect of ecological processes including the promotion of natural enemies to control pests. However, as a last resort, some natural pesticides can be applied such as the pesticide spinosad. This neurotoxic insecticide is now widely used even in non-organic production systems. As generalist predators, spiders, and especially orb web spiders, which prey on flying pests, are thought to be useful for biocontrol. To study the effects of spinosad on orb web spiders, we applied spinosad (Success4®) at the normal application rate (96 g ha-1) in an orchard covered by nets where Araneus diadematus was very abundant. Its abundance (number of webs), location when present on the web and web characteristics were determined one day before (D - 1) and 1, 3, 6, 10 and 14 days after the application (D + 1, D + 3, D + 6, D + 10 and D + 14). After spinosad application, at D + 1 and D + 14, the number of A. diadematus webs decreased by 28% and 47%, respectively, compared to D - 1 where we observed on average 0.2 webs m-2. This decrease is likely due to a combination of direct pesticide effects, reduced prey availability and mechanical effects of the air blast sprayer. The short-term toxicity of spinosad was assessed using behavioural markers: (i) the percentage of abnormally located spiders (i.e. neither in the centre of the web nor hidden under the apple leaves) for 30 and 50% of the webs at D + 1 and D + 3 respectively, (ii) the percentage of incomplete webs (made only of the non-sticky spiral) in 35 and 75% of the cases at D + 1 and D + 3 respectively and (iii) one web characteristic, the mean parallelism between spirals, that was significantly reduced at D + 1 compared to D - 1. The study of the other web characteristics indicated that spiders did not modify the capture area but rather significantly decreased their investment in silk at D + 6 and D + 10 by reducing the number of radii and spiral turns. Overall, the application of spinosad (Success4®), representing a triple disturbance (mechanical, toxicological and alimentary), has a negative impact on the orb web spider A. diadematus and should thus be used with caution if growers want to promote the contribution of these spiders to natural biocontrol in their fields.

The impact of management strategies in apple orchards on the structural and functional diversity of epigeal spiders.

Apple orchards are agro-ecosystems managed with high levels of inputs and especially pesticides. Epigeal spider communities were sampled in three seasons using pitfall traps in 19 apple orchards with four different management strategies (abandoned, under organic, Integrated Pest Management or conventional protection) and thus significantly different pesticide usage. The abundance and diversity of the spider communities was the highest in abandoned orchards. Higher diversity and evenness values were the only difference in spider communities from the organic orchards compared to the other commercial orchards. The analysis of five ecological traits (proportion of aeronauts, type of diet, overwintering stages, body size and maternal care), however, clearly showed differences in the spiders from the organic orchards. The spider species in the other commercial orchards were smaller and have higher dispersal abilities. Seven bioindicator species were identified in abandoned orchards, two species in organic ones (only Lycosidae) and one species in conventional orchards (Linyphiidae).

A shift towards softer pest management differently benefits earwig and spider communities in a multiyear experiment in apple orchards.

BACKGROUND: Environmentally-friendly crop protection practices are needed to enhance the sustainability of current agricultural systems. This is crucial in orchards which are extensively treated to impair various pests, at the expense of natural enemies. However, the effect of a shift towards softer pest management on the beneficial arthropod community is poorly documented. Earwigs (Dermaptera: Forficulidae) and spiders (Araneae) are relevant groups to assess such effects because they are highly sensitive to agricultural practices. They were monitored for 6 and 4 years, respectively, in apple orchards under three pest management regimes: Organic, Low-input and Conventional, with pest management being switched during the survey from a broad-spectrum insecticide schedule to mating disruption in the latter one, and more selective compounds in all orchards. RESULTS: The survey displayed that earwig abundance (mainly Forficula auricularia) that was initially very low in the Conventional orchard (annual mean 0.5-1.7 earwigs per shelter in the 2010-2012 period) increased to the same level as that of Low-input and Organic orchards (over 10 earwigs per shelter) in the same year that changes in pest management occurred. The epigeal and arboreal spider communities were not responsive, and no recovering was observed 4 years after change in practices. CONCLUSION: Predatory arthropod communities are differently affected over time by changes in pest management, most probably due to their biology (dispersion, reproduction rate, susceptibility to pesticides etc.). This outlines the importance of documenting the time required to recover after perturbations and build a natural enemy community to enhance pest control in a win-win perspective. © 2024 Society of Chemical Industry.

Earthworms and plants can decrease soil greenhouse gas emissions by modulating soil moisture fluctuations and soil macroporosity in a mesocosm experiment.

Earthworms can stimulate microbial activity and hence greenhouse gas (GHG) emissions from soils. However, the extent of this effect in the presence of plants and soil moisture fluctuations, which are influenced by earthworm burrowing activity, remains uncertain. Here, we report the effects of earthworms (without, anecic, endogeic, both) and plants (with, without) on GHG (CO2, N2O) emissions in a 3-month greenhouse mesocosm experiment simulating a simplified agricultural context. The mesocosms allowed for water drainage at the bottom to account for the earthworm engineering effect on water flow during two drying-wetting cycles. N2O cumulative emissions were 34.6% and 44.8% lower when both earthworm species and only endogeic species were present, respectively, and 19.8% lower in the presence of plants. The presence of the endogeic species alone or in combination with the anecic species slightly reduced CO2 emissions by 5.9% and 11.4%, respectively, and the presence of plants increased emissions by 6%. Earthworms, plants and soil water content interactively affected weekly N2O emissions, an effect controlled by increased soil dryness due to drainage via earthworm burrows and mesocosm evapotranspiration. Soil macroporosity (measured by X-ray tomography) was affected by earthworm species-specific burrowing activity. Both GHG emissions decreased with topsoil macropore volume, presumably due to reduced moisture and microbial activity. N2O emissions decreased with macropore volume in the deepest layer, likely due to the presence of fewer anaerobic microsites. Our results indicate that, under experimental conditions allowing for plant and earthworm engineering effects on soil moisture, earthworms do not increase GHG emissions, and endogeic earthworms may even reduce N2O emissions.

Community-specific impacts of exotic earthworm invasions on soil carbon dynamics in a sandy temperate forest.

Exotic earthworm introductions can alter above- and belowground properties of temperate forests, but the net impacts on forest soil carbon (C) dynamics are poorly understood. We used a mesocosm experiment to examine the impacts of earthworm species belonging to three different ecological groups (Lumbricus terrestris [anecic], Aporrectodea trapezoides [endogeic], and Eisenia fetida [epigeic]) on C distributions and storage in reconstructed soil profiles from a sandy temperate forest soil by measuring CO2 and dissolved organic carbon (DOC) losses, litter C incorporation into soil, and soil C storage with monospecific and species combinations as treatments. Soil CO2 loss was 30% greater from the Endogeic x Epigeic treatment than from controls (no earthworms) over the first 45 days; CO2 losses from monospecific treatments did not differ from controls. DOC losses were three orders of magnitude lower than CO2 losses, and were similar across earthworm community treatments. Communities with the anecic species accelerated litter C mass loss by 31-39% with differential mass loss of litter types (Acer rubrum > Populus grandidentata > Fagus grandifolia > Quercus rubra > or = Pinus strobus) indicative of leaf litter preference. Burrow system volume, continuity, and size distribution differed across earthworm treatments but did not affect cumulative CO2 or DOC losses. However, burrow system structure controlled vertical C redistribution by mediating the contributions of leaf litter to A-horizon C and N pools, as indicated by strong correlations between (1) subsurface vertical burrows made by anecic species, and accelerated leaf litter mass losses (with the exception of P. strobus); and (2) dense burrow networks in the A-horizon and the C and N properties of these pools. Final soil C storage was slightly lower in earthworm treatments, indicating that increased leaf litter C inputs into soil were more than offset by losses as CO2 and DOC across earthworm community treatments.

Earthworms do not increase greenhouse gas emissions (CO2 and N2O) in an ecotron experiment simulating a three-crop rotation system.

Earthworms are known to stimulate soil greenhouse gas (GHG) emissions, but the majority of previous studies have used simplified model systems or lacked continuous high-frequency measurements. To address this, we conducted a 2-year study using large lysimeters (5 m2 area and 1.5 m soil depth) in an ecotron facility, continuously measuring ecosystem-level CO2, N2O, and H2O fluxes. We investigated the impact of endogeic and anecic earthworms on GHG emissions and ecosystem water use efficiency (WUE) in a simulated agricultural setting. Although we observed transient stimulations of carbon fluxes in the presence of earthworms, cumulative fluxes over the study indicated no significant increase in CO2 emissions. Endogeic earthworms reduced N2O emissions during the wheat culture (- 44.6%), but this effect was not sustained throughout the experiment. No consistent effects on ecosystem evapotranspiration or WUE were found. Our study suggests that earthworms do not significantly contribute to GHG emissions over a two-year period in experimental conditions that mimic an agricultural setting. These findings highlight the need for realistic experiments and continuous GHG measurements.

Integrating earthworm movement and life history through dynamic energy budgets.

Earthworms are considered ecosystem engineers and, as such, they are an integral part of the soil ecosystem. The movement of earthworms is significantly influenced by environmental factors such as temperature and soil properties. As movement may directly be linked to food ingestion, especially of endogeic species like Aporrectodea caliginosa, changes in those environmental factors also affect life history traits such as growth and reproduction. In our laboratory studies, earthworms showed a decrease in burrowing activity with decreasing moisture levels and, to some extent, the organic matter content. The burrowing activity of earthworms was also affected by temperature, for which the casts produced per earthworm was used as a proxy in laboratory experiments. We integrated changes in earthworm movement and life histories in response to temperature, soil organic matter content and the moisture level, as observed in our experiment and reported in the literature, through dynamic energy budget (DEB) modelling. The joint parametrization of a DEB model for A. caliginosa based on movement and life history data revealed that food ingestion via movement is an integral part of the earthworms' energy budgets. Our findings highlight the importance of soil properties to be considered in the model development for earthworms. Furthermore, by understanding and incorporating the effect of environmental factors on the physiology, this mechanistic approach can help assess the impact of environmental changes such as temperature rise or drought.

Making Waves: Modeling bioturbation in soils - are we burrowing in the right direction?

The burrowing, feeding and foraging activities of terrestrial and benthic organisms induce displacements of soil and sediment materials, leading to a profound mixing of these media. Such particle movements, called "sediment reworking" in aquatic environments and "bioturbation" in soils, have been thoroughly studied and modeled in sediments, where they affect organic matter mineralization and contaminant fluxes. In comparison, studies characterizing the translocation, by soil burrowers, of mineral particles, organic matter and adsorbed contaminants are paradoxically fewer. Nevertheless, models borrowed from aquatic ecology are used to predict the impact of bioturbation on organic matter turnover and contaminant transport in the soil. However, these models are based on hypotheses that have not been tested with adequate observations in soils, and may not necessarily reflect the actual impact of soil burrowers on particle translocation. This paper aims to (i) highlight the possible shortcomings linked to the current use of sediment reworking models for soils, (ii) identify how recent progresses in aquatic ecology could help to circumvent these limitations, and (iii) propose key steps to ensure that soil bioturbation models are built on solid foundations: more accurate models of organic matter turnover, soil evolution and contaminant transport in the soil are at stake.

How lasting are the effects of pesticides on earwigs? A study based on energy metabolism, body weight and morphometry in two generations of Forficula auricularia from apple orchards.

Widespread use of pesticides to control pests is the dominant system in conventional apple orchards. To avoid adverse side effects, there is a growing interest in promoting alternative methods including biological control based on the use of natural enemies. The European earwig Forficula auricularia L. (Dermaptera: Forficuidae) is an effective predator in apple orchards. Pesticide pressure has been shown to divert energy resources which could have a negative impact on life history traits. In this study we assessed (i) whether variations in pesticide exposure could differentially impact energy reserves, body weight and morphometric parameters of F. auricularia, and (ii) whether these effects persist into the next generation reared under optimal conditions. Individuals from the first generation were collected in late October from organic, IPM and conventional orchards. The next generation was obtained under a rearing program, in the absence of pesticide exposure. Earwigs collected from conventional orchards exhibited lower values for all morphometric parameters compared to those collected in organic orchards. However, a relaxed period without pesticide exposure (in autumn) appears to have allowed the females to recover their energy reserves to ensure reproduction and maternal care. Glycogen contents were the reserves that were more easily restored. However, probably due to the rearing conditions (food ad libitum), all the earwigs from the second generation exhibited higher body weights and energy reserves than their parents.

Elucidating pesticide sensitivity of two endogeic earthworm species through the interplay between esterases and glutathione S-transferases.

Earthworms are common organisms in soil toxicity-testing framework, and endogeic species are currently recommended due to their ecological role in agroecosystem. However, little is known on their pesticide metabolic capacities. We firstly compared the baseline activity of B-esterases and glutathione-S-transferase in Allolobophora chlorotica and Aporrectodea caliginosa. Secondly, vulnerability of these species to pesticide exposure was assessed by in vitro trials using the organophosphate (OP) chlorpyrifos-ethyl-oxon (CPOx) and ethyl-paraoxon (POx), and by short-term (7 days) in vivo metabolic responses in soil contaminated with pesticides. Among B-esterases, acetylcholinesterase (AChE) activity was abundant in the microsomal fraction (80% and 70% of total activity for A. caliginosa and A. chlorotica, respectively). Carboxylesterase (CbE) activities were measured using three substrates to examine species differences in isoenzyme and sensitivity to both in vitro and in vivo exposure. CbEs were mainly found in the cytosolic fraction (80% and 60% for A. caliginosa and A. chlorotica respectively). GST was exclusively found in the soluble fraction for both species. Both OPs inhibited B-esterases in a concentration-dependent manner. In vitro trials revealed a pesticide-specific response, being A. chlorotica AChE more sensitive to CPOx compared to POx. CbE activity was inhibited at the same extent in both species. The 7-d exposure showed A. chlorotica less sensitive to both OPs, which contrasted with outcomes from in vitro experiments. This non-related functional between both approaches for assessing pesticide toxicity suggests that other mechanisms linked with in vivo OP bioactivation and excretion could have a significant role in the OP toxicity in endogeic earthworms.

Experimental simulation of environmental warming selects against pigmented morphs of land snails.

In terrestrial snails, thermal selection acts on shell coloration. However, the biological relevance of small differences in the intensity of shell pigmentation and the associated thermodynamic, physiological, and evolutionary consequences for snail diversity within the course of environmental warming are still insufficiently understood. To relate temperature-driven internal heating, protein and membrane integrity impairment, escape behavior, place of residence selection, water loss, and mortality, we used experimentally warmed open-top chambers and field observations with a total of >11,000 naturally or experimentally colored individuals of the highly polymorphic species Theba pisana (O.F. MÜller, 1774). We show that solar radiation in their natural Mediterranean habitat in Southern France poses intensifying thermal stress on increasingly pigmented snails that cannot be compensated for by behavioral responses. Individuals of all morphs acted neither jointly nor actively competed in climbing behavior, but acted similarly regardless of neighbor pigmentation intensity. Consequently, dark morphs progressively suffered from high internal temperatures, oxidative stress, and a breakdown of the chaperone system. Concomitant with increasing water loss, mortality increased with more intense pigmentation under simulated global warming conditions. In parallel with an increase in mean ambient temperature of 1.34°C over the past 30 years, the mortality rate of pigmented individuals in the field is, currently, about 50% higher than that of white morphs. A further increase of 1.12°C, as experimentally simulated in our study, would elevate this rate by another 26%. For 34 T. pisana populations from locations that are up to 2.7°C warmer than our experimental site, we show that both the frequency of pigmented morphs and overall pigmentation intensity decrease with an increase in average summer temperatures. We therefore predict a continuing strong decline in the frequency of pigmented morphs and a decrease in overall pigmentation intensity with ongoing global change in areas with strong solar radiation.

Mechanistic Effect Modeling of Earthworms in the Context of Pesticide Risk Assessment: Synthesis of the FORESEE Workshop.

Earthworms are important ecosystem engineers, and assessment of the risk of plant protection products toward them is part of the European environmental risk assessment (ERA). In the current ERA scheme, exposure and effects are represented simplistically and are not well integrated, resulting in uncertainty when the results are applied to ecosystems. Modeling offers a powerful tool to integrate the effects observed in lower tier laboratory studies with the environmental conditions under which exposure is expected in the field. This paper provides a summary of the (In)Field Organism Risk modEling by coupling Soil Exposure and Effect (FORESEE) Workshop held 28-30 January 2020 in Düsseldorf, Germany. This workshop focused on toxicokinetic-toxicodynamic (TKTD) and population modeling of earthworms in the context of ERA. The goal was to bring together scientists from different stakeholder groups to discuss the current state of soil invertebrate modeling and to explore how earthworm modeling could be applied to risk assessments, in particular how the different model outputs can be used in the tiered ERA approach. In support of these goals, the workshop aimed at addressing the requirements and concerns of the different stakeholder groups to support further model development. The modeling approach included 4 submodules to cover the most relevant processes for earthworm risk assessment: environment, behavior (feeding, vertical movement), TKTD, and population. Four workgroups examined different aspects of the model with relevance for risk assessment, earthworm ecology, uptake routes, and cross-species extrapolation and model testing. Here, we present the perspectives of each workgroup and highlight how the collaborative effort of participants from multidisciplinary backgrounds helped to establish common ground. In addition, we provide a list of recommendations for how earthworm TKTD modeling could address some of the uncertainties in current risk assessments for plant protection products. Integr Environ Assess Manag 2021;17:352-363. © 2020 SETAC.

Global data on earthworm abundance, biomass, diversity and corresponding environmental properties.

Earthworms are an important soil taxon as ecosystem engineers, providing a variety of crucial ecosystem functions and services. Little is known about their diversity and distribution at large spatial scales, despite the availability of considerable amounts of local-scale data. Earthworm diversity data, obtained from the primary literature or provided directly by authors, were collated with information on site locations, including coordinates, habitat cover, and soil properties. Datasets were required, at a minimum, to include abundance or biomass of earthworms at a site. Where possible, site-level species lists were included, as well as the abundance and biomass of individual species and ecological groups. This global dataset contains 10,840 sites, with 184 species, from 60 countries and all continents except Antarctica. The data were obtained from 182 published articles, published between 1973 and 2017, and 17 unpublished datasets. Amalgamating data into a single global database will assist researchers in investigating and answering a wide variety of pressing questions, for example, jointly assessing aboveground and belowground biodiversity distributions and drivers of biodiversity change.

Physiological and behavioural effects of imidacloprid on two ecologically relevant earthworm species (Lumbricus terrestris and Aporrectodea caliginosa).

Earthworms play key roles in soils and sub-lethal effects of environmental toxicants on these organisms should be taken seriously, since they might have detrimental effects on higher ecological levels. In laboratory experiments we have assessed sub-lethal effects (body mass change and cast production) of imidacloprid on two earthworm species commonly found in different agricultural soils (Lumbricus terrestris and Aporrectodea caliginosa). After 7 days of exposure in contaminated soil, a significant loss of body mass was found in both species exposed to imidacloprid concentrations as low as 0.66 mg kg(-1) dry soil. These losses ranged from 18.3 to 39% for A. caliginosa and from 7.4 to 32.4% for L. terrestris, respectively. Changes in cast production, a new biomarker previously validated using L. terrestris, was assessed by soil sieving using the recommended mesh size (5.6 mm) for L. terrestris and three different mesh sizes for A. caliginosa (5.6, 4 and 3.15 mm). The 4 mm mesh size proved to be the most suitable sieve size for A. caliginosa. Cast production increased by 26.2% in A. caliginosa and by 28.1% in L. terrestris at the lowest imidacloprid concentration tested (0.2 mg kg(-1) dry soil), but significantly decreased at higher concentrations (equal to and above 0.66 mg kg(-1) dry soil) in both earthworm species after the 7 days exposure experiment. These decreases in cast production ranged from 44.5 to 96.9% in A. caliginosa and from 42.4 to 95.7% in L. terrestris. The EC(50) for cast production were 0.84 (L. terrestris) and 0.76 mg kg(-1) dry soil (A. caliginosa), respectively. The detected sub-lethal effects were found close to the predicted environmental concentration (PEC) of imidacloprid, which is in the range of 0.33-0.66 mg kg(-1) dry soil. The biomarkers used in the present study, body mass change and changes in cast production, may be of ecological relevance and have shown high sensitivity for imidacloprid exposure of earthworms. The measurement of changes in cast production should be considered for inclusion in current standard tests.

Towards a spatiotemporally explicit toxicokinetic-toxicodynamic model for earthworm toxicity.

The aim of the environmental risk assessment of chemicals is the prevention of unacceptable adverse effects on the environment. Therefore, the risk assessment for in-soil organisms, such as earthworms, is based on two key elements: the exposure assessment and the effect assessment. In the current risk assessment scheme, these two elements are not linked. While for the exposure assessment, advanced exposure models can take the spatial and temporal scale of substances into account, the effect assessment in the lower tiers considers only a limited temporal and spatial variability. However, for soil organisms, such as earthworms, those scales play a significant role as species move through the soil in response to environmental factors. To overcome this gap, we propose a conceptual integration of pesticide exposure, ecology, and toxicological effects on earthworms using a modular modeling approach. An essential part of this modular approach is the environment module, which utilizes exposure models to provide spatially and temporally explicit information on environmental variables (e.g., temperature, moisture, organic matter content) and chemical concentrations. The behavior module uses this information and simulates the feeding and movement of different earthworm species using a trait-based approach. The resulting exposure can be processed by a toxicokinetic-toxicodynamic (TKTD) module. TKTD models are particularly suitable to make effect predictions for time-variable exposure situations as they include the processes of uptake, elimination, internal distribution, and biotransformation of chemicals and link the internal concentration to an effect at the organism level. The population module incorporates existing population models of different earthworm species. The modular approach is illustrated using a case study with an insecticide. Our results emphasize that using a modular model approach will facilitate the integration of exposure and effects and thus enhance the risk assessment of soil organisms.

Snail phenotypic variation and stress proteins: do different heat response strategies contribute to Waddington's widget in field populations?

On the basis of studies with laboratory strains of Drosophila and Arabidopsis, it has been hypothesized that potential buffers to the expression of phenotypic morphological variation, such as Hsp90 and possibly Hsp70, represent important components of Waddington's widget, which may confer capacitive evolution. As studies on field populations of living organisms to test this hypothesis are lacking, we tested whether a heat response strategy involving high stress protein levels is associated with low morphological variation and vice versa, using four natural populations of Mediterranean pulmonate snails. In response to 8 hr of elevated temperatures, a population of Xeropicta derbentina with uniform shell pigmentation pattern showed remarkably high Hsp70 but low Hsp90 levels. In contrast, a highly variable population of Cernuella virgata kept both Hsp90 and Hsp70 levels low when held at diverse though environmentally relevant temperatures. Two other populations (Theba pisana and another X. derbentina population) with intermediate variation in shell pigmentation pattern were also intermediate in inducing Hsp70, though Hsp90 was maintained at a low level. The observed correlation of stress protein levels and coloration pattern variation provide the first indirect evidence for an association of stress proteins with Waddington's widget under natural conditions.

Metabolic mechanisms and acetylcholinesterase sensitivity involved in tolerance to chlorpyrifos-ethyl in the earwig Forficula auricularia.

Apple orchards are highly treated crops, in which organophosphorus (OP) are among the most heavily sprayed insecticides. These pesticides are toxic to non-target arthropods and their repeated use increases the risk of resistance. We studied mechanisms involved in tolerance and resistance to OP insecticides in the earwig Forficula auricularia, an effective generalist predator in pomefruit orchards. Adult earwigs were sampled in three apple orchards managed under contrasting strategies: conventional, Integrated Pest Management, and organic. The threshold activities of enzyme families involved in pesticides tolerance: Glutathione-S-transferases (GSTs) and Carboxylesterases (CbEs) were measured in earwig extracts. Acetylcholinesterase (AChE) was monitored as a toxicological endpoint. Variations in these activities were assessed prior to and after exposure to chlorpyrifos-ethyl at the normal application rate. We observed that the mortality of earwigs exposed to chlorpyrifos-ethyl depended on the management strategy of orchards. Significantly lower mortality was seen in individuals sampled from conventional orchard. The basal activities of CbEs and GSTs of collected organisms were higher in conventional orchard. After in vivo exposure, AChE activity appeared to be inhibited in surviving males with no difference between orchards. However an in vitro inhibition trial with chlorpyrifos-oxon showed that AChE from earwigs collected in organic and IPM orchards were more sensitive than from conventional ones. These observations support the hypothesis of a molecular target modification in AChE and highlight the possible role of CbEs in effective protection of AChE. Our findings suggest that the earwigs with a high historic level of insecticide exposure could acquire resistance to chlorpyrifos-ethyl.

Influence of earthworm bioturbation on metals phytoavailability and human gastric bioaccessibility.

At the global scale, urban agriculture is increasingly developing in cities due to demographic growth and sustainable food concerns. But, urban soils are frequently polluted with metals. In urban gardens, organic matter is also commonly added both to valorize organic household waste and to promote biophysicochemical fertility. As earthworms promote the decomposition and the recycling of soil organic matter, they can also influence the biogeochemical cycle of metals in urban polluted soils. In order to produce safe vegetables in urban areas, it is crucial to highlight the mechanisms involved in complex soil-earthworm-plant ecosystems. An experiment was set up to examine these relationships using lettuce cultivated in controlled conditions with RHIZOtest® devices. Thanks to the RHIZOtest® devices, metal transfer and bioaccessibility were for the first time compared for urban polluted soil without (1-urban soil polluted with Pb, Cd, Cu, and Zn: essential or toxic metals currently found in environment, SNB) and with bioturbation (2-this metal-polluted soil subjected to earthworm bioturbation, SB) and earthworm casts (3-earthworm casts produced in this polluted soil and naturally enriched in organic matter and microorganisms, T). Metal concentration, phytoavailability, and human gastric bioaccessibility were determined in the different samples. Results showed that earthworm bioturbation increased the phytoavailability of all the metals. For the experimental condition SB, the phytoavailability of metals was increased up to 75% compared to SNB. In addition, surprisingly, metal phytoavailability was always superior in SB compared to earthworm casts (T). Moreover, earthworms led to an increase in Zn gastric bioaccessibility up to 10% in the soils in the same way as for phytoavailability, meaning Zn bioaccessibility in SB > T > SNB, whereas it remained unchanged in the lettuces. These data are important to promote sustainable agriculture activities in urban areas; actually, databases concerning different experimental conditions are needed to develop decision support tools.

Global distribution of earthworm diversity.

Soil organisms, including earthworms, are a key component of terrestrial ecosystems. However, little is known about their diversity, their distribution, and the threats affecting them. We compiled a global dataset of sampled earthworm communities from 6928 sites in 57 countries as a basis for predicting patterns in earthworm diversity, abundance, and biomass. We found that local species richness and abundance typically peaked at higher latitudes, displaying patterns opposite to those observed in aboveground organisms. However, high species dissimilarity across tropical locations may cause diversity across the entirety of the tropics to be higher than elsewhere. Climate variables were found to be more important in shaping earthworm communities than soil properties or habitat cover. These findings suggest that climate change may have serious implications for earthworm communities and for the functions they provide.

Nerve conduction velocity as a non-destructive biomarker in the earthworm Aporrectodea caliginosa exposed to insecticides.

Earthworms are important and useful soil organisms, but in agricultural soils, they are potentially exposed to a wide variety of pesticides. Insecticides represent the highest threat to earthworms and many are neurotoxic. There is a need for a reliable, relevant, simple biomarker to assess the sub-lethal effects of neurotoxic insecticides on earthworms under laboratory or field conditions. The Aporrectodea caliginosa earthworms were exposed to 0 (control), 0.5×, 1× (normal field application rate), and 5× concentrations of a carbamate (Pirimor®) and an organophosphate (Lorsban®) insecticides. The nerve conduction velocity (NCV) of the medial giant fibers of A. caliginosa earthworm was recorded on days 0, 1, 2, 3, 4, and 7 to quantify sub-lethal neurotoxic effects. Acetylcholinesterase (AChE) enzyme activity of A. caliginosa homogenates was measured at the conclusion of the experiment. Pirimor® but not Lorsban® induced a significant decrease in NCV on days 3, 4, and 7 at 1× and 5× doses. A significant dose-dependent decrease was observed on AChE activity to Pirimor® at the doses used but not Lorsban®. A clear relationship is observed between AChE activity and NCV in the case of Pirimor®. This study showed that NCV is a sensitive biomarker that correlates well with classical biomarker measurements such as AChE enzyme activity. This technique could be used to study the impact of insecticides on earthworms and also their recovery.