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Earthworm burrow systems are generally described based on postulated behaviours associated with the three ecological types. In this study, we used X-ray tomography to obtain 3D information on the burrowing behaviour of six very common anecic ( Aporrectodea nocturna and Lumbricus terrestris ) and endogeic ( Aporrectodea rosea , Allolobophora chlorotica , Aporrectodea caliginosa , Aporrectodea icterica ) earthworm species, introduced into repacked soil cores for 6 weeks. A simple water infiltration test, the Beerkan method, was also used to assess some functional properties of these burrow systems. Endogeic worms make larger burrow systems, which are more highly branched, less continuous and of smaller diameter, than those of anecic worms. Among the anecic species, L. terrestris burrow systems are shorter (9.2 vs 21.2 m) with a higher number (14.5 vs 23.5) of less branched burrows (12.2 vs 20.2 branches m −1 ), which are also wider (7.78 vs 5.16 mm) than those of A. nocturna . In comparison, the burrow systems made by endogeic species appeared similar to each other. However, A. rosea burrows were short and narrow, whereas A. icterica had a longer burrow system (15.7 m), more intense bioturbation intensity (refilled macropores or soil lateral compaction around them) and thus a greater number of burrows. Regarding water infiltration, anecic burrow systems were far more efficient due to open burrows linking the top and bottom of the cores. For endogeic species, we observed a linear relationship between burrow length and the water infiltration rate ( R 2  = 0.49, p  < 0.01). Overall, the three main characteristics significantly influencing water infiltration were burrow length, burrow number and bioturbation volume. This last characteristic highlighted the effect of burrow refilling by casts.

Earthworms feed on organic matter present at the soil surface or within the soil. Thus, its distribution in the soil profile is likely to greatly influence earthworm behavior and, in turn, their burrow system. To test this idea, two anecic and two endogeic earthworm species were introduced into repacked soil cores (depth = 30 cm) upper half filled with a top soil containing 4% organic matter (0–15 cm) and lower half filled with a deep soil at 2% organic matter (15–30 cm). Earthworm behavior was studied using X-ray tomography combined with luminophores (colored particulate tracers of 63–125 μm size) placed at 0, 3, and 12 cm depth, a method widely used in sediment ecology. We observed that anecic and endogeic earthworms had contrasting reactions to the conditions with only endogeic species burrowing more intensively in the upper part. From a quantitative point of view, only a few percent of luminophores were displaced. However, luminophore displacements also provided qualitative information to complement the tomography: (i) endogeic species and especially Aporrectodea caliginosa bioturbated the most soil close to the surface (3 cm depth) and (ii) the two anecic species influenced the luminophore distribution differentially with Lumbricus terrestris displacing significantly more luminophores, whatever their initial depth, than Aporrectodea nocturna due to intense surface cast activity. Beyond methodological developments, our study found that endogeic earthworms burrow more in zones with higher organic matter contents and this explains why they are mainly found close to the soil surface in non-tilled soils.

Ecotoxicological tests with earthworms are widely used and are mandatory for the risk assessment of pesticides prior to registration and commercial use. The current model species for standardized tests is Eisenia fetida or Eisenia andrei. However, these species are absent from agricultural soils and often less sensitive to pesticides than other earthworm species found in mineral soils. To move towards a better assessment of pesticide effects on non-target organisms, there is a need to perform a posteriori tests using relevant species. The endogeic species Aporrectodea caliginosa (Savigny, 1826) is representative of cultivated fields in temperate regions and is suggested as a relevant model test species. After providing information on its taxonomy, biology, and ecology, we reviewed current knowledge concerning its sensitivity towards pesticides. Moreover, we highlighted research gaps and promising perspectives. Finally, advice and recommendations are given for the establishment of laboratory cultures and experiments using this soil-dwelling earthworm species.

Earthworms are an important prey for the endangered meadow birds of northwest Europe. Although intensive grassland management with high manure inputs generally promotes earthworm abundance, it may reduce the effective food availability for meadow birds through desiccation of the topsoil, which causes earthworms to remain deeper in the soil. We studied the response of Red Worm Lumbricus rubellus, a detritivore, and Grey Worm Aporrectodea caliginosa, a geophage, to soil moisture profiles in the field and under experimental conditions. Surfacing earthworms were counted weekly in eight intensively managed grasslands (treated with high inputs of slurry by slit injection) with variable groundwater tables in the Netherlands. At each count, soil penetration resistance, soil moisture tension and groundwater level were measured, while air temperature and humidity were obtained from a nearby weather station. The response to variation in the vertical distribution of soil moisture was also experimentally studied in the two earthworm species. In the field, earthworms’ surfacing activity at night was negatively associated with soil moisture tension and positively by relative air humidity. Surprisingly, there was no effect of groundwater level; an important management variable in meadow bird conservation. Under experimental conditions, both L. rubellus and A. caliginosa moved to deeper soil layers (>20 cm) in drier soil moisture treatments, avoiding the upper layer when moisture levels dropped below 30%. Synthesis and applications. We propose that in intensively managed grasslands with slurry application, topsoil desiccation reduces earthworm availability for meadow birds. This can be counteracted by keeping soil moisture tensions of the top soil above −15 kPa. We suggest that the late raising of groundwater tables in spring and the disturbance of the soil by slit injection of slurry increase topsoil desiccation. This decreases earthworm availability when it matters most for breeding meadow birds. Meadow bird conservation will benefit from revised manure application strategies that promote earthworm activity near or at the soil surface. Foreign Language Samenvatting Regenwormen zijn een belangrijke prooi voor weidevogels in Noordwest‐Europa. Hoewel intensief landgebruik met een hoge mestgift over het algemeen resulteert in hoge dichtheden aan regenwormen, zou het wellicht de beschikbaarheid voor weidevogels kunnen verlagen doordat de toplaag van de bodem sneller uitdroogt waardoor regenwormen dieper in de grond blijven. We onderzochten de response van de Rode Worm Lumbricus rubellus, een detritus‐eter, en van de Grijze Worm Aporrectodea caliginosa, een bodem‐eter, op verschillende bodemvochtcondities in het veld in graslanden die gebruikt worden in de melkveehouderij en in het lab onder gecontroleerde omstandigheden. In Zuidwest‐Friesland werden in het voorjaar van 2015 op acht graslanden met hetzelfde intensieve beheer (bemesting d.m.v. drijfmestinjectie) en bodemtype, maar met verschillende grondwaterpeilen, wekelijks oppervlakte‐actieve regenwormen geteld. Bij elke telling werd ook bodemdoordringbaarheid, bodemvochtspanning en grondwaterpeil gemeten. Meteorologische data werd verzameld bij een weerstation in de buurt. In het lab werd gekeken naar de verticale distributie van de twee soorten regenwormen bij verschillende bodemvocht omstandigheden. De oppervlakte‐activiteit van regenwormen wordt bepaald door hoge luchtvochtigheid en lage bodemvochtspanning. Verrassend genoeg vonden we geen effect van grondwaterpeil op regenwormen activiteit. Beide soorten regenwormen gaan dieper de bodem in wanneer het bodemvochtgehalte in te toplaag onder de 30% zakt. Synthese en toepassingen. In intensief beheerd grasland dat bemest wordt door middel van drijfmestinjectie, neemt de beschikbaarheid van regenwormen voor weidevogels af door uitdroging van de toplaag van de bodem. Dit kan worden voorkomen door de toplaag vochtig te houden met een vochtspanning hoger dan ‐15kPa. Omdat we geen effect van grondwaterpeil vonden, denken we dat in deze graslanden het te laat omhoog brengen van het grondwaterpeil in het voorjaar en het gebruik van mestinjectie het uitdrogen van de bodemtoplaag heeft versterkt. Weidevogelbeheer zou dus gebaat zijn bij een andere vorm bemesting dat regenwormen activiteit aan of vlakbij het bodemoppervlak promoot. We propose that in intensively managed grasslands with slurry application, topsoil desiccation reduces earthworm availability for meadow birds. This can be counteracted by keeping soil moisture tensions of the top soil above −15 kPa. We suggest that the late raising of groundwater tables in spring and the disturbance of the soil by slit injection of slurry increase topsoil desiccation. This decreases earthworm availability when it matters most for breeding meadow birds. Meadow bird conservation will benefit from revised manure application strategies that promote earthworm activity near or at the soil surface.

We present for the first time the complete mitochondrial genomes (mt genomes) of the earthworms Aporrectodea caliginosa and Ap. trapezoides (Clitellata, Megadrili) collected in Hungary and Korea, respectively. The complete mt genome of Ap. trapezoides comprised 15,014 base pairs. Lengths of the three complete Ap. caliginosa mt genomes varied between 15,090 and 15,123 bp. All four mt genomes contained 13 protein-coding genes (PCGs), two rRNA genes, 22 tRNA genes, and one major non-coding control region. These mt genome arrangements are identical to those observed in the mt genomes of most earthworms, and all the 37 genes are transcribed from the same directional strand. All 13 PCGs had the same ATG start codon. Most of the PCGs end with TAA or TAG, whereas the remaining end with an incomplete stop codon, T. Stop codons were consistent in the PCGs throughout the mt genomes, except Ap. caliginosa 5, which contains a TAG stop codon in ND5 instead of the TAA found in the other samples. Both species’ genomes showed biased base composition, with 63.5% AT and 36.4% GC content in Ap. trapezoides and 62.8% and 37.2% in Ap. caliginosa . Phylogenetic analysis of the mt genomes corroborated the monophyly of the family Lumbricidae and the close relationship between Ap. trapezoides and Ap. caliginosa species pairs. The available Ap. tuberculata sequences were embedded between the Ap. caliginosa samples, thereby supporting the synonymy of the two names.

Soil and earthworms are threatened by anthropogenic contamination resulting from olive mill waste dumping on the soil due to their pollutant properties. While several studies have explored the effects of olive mill waste on soil properties and the accumulation of heavy metals in soil, there is currently a gap in the literature regarding the potential bioaccumulation of heavy metals from olive mill waste in earthworms. In this study, soil with earthworms from two ecological categories (endogeic: Aporrectodea trapezoides and epigeic: Eisenia fetida ) was treated with increasing doses of olive mill wastewater (OMWW) and olive mill pomace (OMP), applied individually or combined, in an indoor experiment in plastic containers, under laboratory conditions. The results revealed the presence of significant concentrations of heavy metals in the two types of wastes ranging as follows: Fe˃ Zn˃ Cu˃ Cd˃ Cr for OMWW, and Fe˃ Zn˃ Cu˃ Cr for OMP (with Cd below the detection limit). The study demonstrated distinct effects of OMWW and OMP, both individually and in combination, on soil heavy metal content, ranging as follows: soil OMWW > soil Combination > soil OMP for Cd; soil Combination > soil OMWW > soil OMP for Cr and Fe; and soil Combination > soil OMP > soil OMWW for Cu and Zn. Additionally, our investigation showed that both earthworm species exhibited significant uptake of these metals into their tissues, particularly the endogeic species. Interestingly, the most significant difference between species was in the accumulation of Cu, with the epigeic species accumulating significantly lower amounts. Graphical Abstract

Invasive plants often modify soil biotic communities through changes in soil physicochemical characteristics or the amount and/or quality of litter inputs. We assessed the impacts of Gunnera tinctoria invasions on soil and the earthworm community, on Achill Island, Co. Mayo, Ireland. We compared replicated (n = 5) areas invaded by G. tinctoria with uninvaded semi-natural grasslands, as well as with areas subjected to mechanical removal or herbicide treatment. Modifications in physiochemical properties included lower soil temperatures and higher soil pH during the summer in invaded areas, yet little effect on C and N stocks, or soil moisture. Marked differences in litter were observed, however, with invaded areas having c. 20-fold higher (above-ground) litter input than uninvaded ones, as well as lower C:N ratio (17 vs. 29). This was associated with a significantly higher overall abundance and biomass of earthworms in invaded plots (375 individuals m–2, 115 g biomass m–2), compared to the uninvaded control (130 individuals m–2, 45 g biomass m–2), with removal treatments having intermediate values. Earthworm communities comprised 10 species, typical for Irish grasslands, dominated by the common endogeic species Allolobophora chlorotica, Aporrectodea caliginosa and Aporrectodea rosea. Both earthworm species richness and Shannon diversity were significantly higher in invaded areas, but only in spring samples. Based on this new information, plant invaders may increase the abundance and diversity of earthworms, mainly due to much larger litter inputs, increased soil pH and possibly lower soil temperatures in the summer.

Effects of mowing on vegetation parameters have been well studied. However, less is known about mowing effects on soil fauna and if soil properties alter this. We investigated earthworm communities in a long-term experiment 14 years after its establishment in 5 dry, fresh and moist grassland plots located in the Natura 2000 site Lainzer Tiergarten near Vienna, Austria (238–402 m a.s.l., 48°10′ N, 16°12′ E). The grasslands were either mowed once a year or every second year, or not mowed since being established. Earthworms were assessed using the non-destructive octet electro-shocking method. Additionally, vegetation composition, soil conductivity, temperature and moisture were assessed. We found 13 earthworm species across all treatments, although their abundance was generally low with 6.1 ± 4.7 worms m−2. The total earthworm abundance and species diversity was higher in dry compared to fresh and moist grasslands but was not affected by mowing frequency. Endogeic earthworms (Aporrectodea caliginosa, Aporrectodea rosea) and epigeics (Lumbricus rubellus) were more tolerant to mowing than anecics (Lumbricus terrestris, Allolobophora longa). Since plant species richness was highest in annually mown grasslands and earthworm species richness was positively related to plant species numbers, we recommend regular, low-input management to promote above- and belowground biodiversity in these grasslands.

Verminephrobacter, the most common specific symbionts in the nephridia (excretory organs) of lumbricid earthworms, have been shown to improve reproduction of the garden earthworm Aporrectodea tuberculata under nutrient limitation. It is unknown how general this beneficial trait is in the Verminephrobacter-earthworm symbiosis, whether other nephridial symbionts also affect host fitness and what the mechanism of the fitness increase is. Here we report beneficial effects of Verminephrobacter and Candidatus Nephrothrix on life history traits of the compost worm Eisenia andrei, which in addition to these two symbionts also hosts Agromyces-like bacteria in its mixed nephridial community: while growth was identical between control, Verminephrobacter-free and aposymbiotic worms, control worms produced significantly more cocoons and offspring than both Verminephrobacter-free and aposymbiotic worms, confirming the reproductive benefit of Verminephrobacter in a second host with different ecology and feeding behavior. Furthermore, worms with Verminephrobacter and Ca. Nephrothrix, or with only Ca. Nephrothrix present, reached sexual maturity significantly earlier than aposymbiotic worms; this is the first evidence for a beneficial role of Ca. Nephrothrix in earthworms. Riboflavin content in cocoons and whole earthworms was unaffected by the presence or absence of nephridial symbionts, suggesting that nutritional supplementation with this vitamin does not play a major role in this symbiosis.

Alternative storm water management focuses on channeling rainwater to underground reservoirs, decreasing the surface flow, and reducing the load of wastewater treatment systems in urban planning. However, soil permeability is a major hindrance to alternative management techniques. Increasing soil permeability is necessary to manage rainwater harvesting and increase groundwater recharge. Additionally, earthworm density directly affects soil properties. In this study, we investigated the effects of earthworm density and species on the permeability of clay loam soil by a gravity-driven film flow. We conducted indoor and outdoor experiments by installing boxes/tanks with layers of materials (gravel, textile, clay loam soil, and organic matter). In the indoor experiments (IE), these materials were used to feed individuals of Lumbricus terrestris with an initial density of 25/m², 50/m², 100/m² while the outdoor experiments (OE) had the initial density of 108/m². All experiments were conducted in triplicate. The permeability velocity was measured using the gravity-driven film flow method with a flow rate of 1 cm/unit time. The coefficient of determination R² of 0.86, 0.93, 0.93 between infiltration velocity and time variable was determined using the data on the initial earthworm density in the IE in one year. Moreover, the growth percentage of L100 was the highest value at 1347% in 391st days. Meanwhile, in the OE, compared to the OE with two earthworms ( Lumbricus terrestris and Aporrectodea caliginosa ), the infiltration velocity of contained tanks by A. caliginosa were significantly greater than the ones by L. terrestris at 289% and 155%, respectively. The coefficient of determination R² of 0.89, 0.89, 0.98 between infiltration velocity and time variable was collected by the initial presence of two earthworm species for one year. The results of the experiment showed that burrowing earthworms can significantly facilitate the infiltration velocity of clay loam soil, and the density of earthworms was found to affect the capacity of permeability, based on the gravity-driven film flow methodology. This also illustrates that the two functional groups have different interactions with the infiltration velocity. Data provided in this study could be used to apply the functional earthworms in ameliorating the alternative techniques in stormwater management systems.