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Transport by earthworms contributes to the secondary dispersal of seeds and influences patterns of plant community structure and function. To date, however, research on earthworm seed dispersal has focused primarily on vertical transport and the collection of seeds into middens at the soil surface, with no efforts to map horizontal distribution after burial. This study used an emergence depth assay and depth-stratified seedling emergence from soil microcosm cross-sections to map earthworm seed transport in three dimensions using commercial grass seed and the anecic earthworm Lumbricus terrestris L. While specific seed burial profiles should not be considered representative of burial under field conditions (due primarily to high earthworm densities under artificially limiting microcosm conditions), we created what we believe to be the first three-dimensional and most detailed map of earthworm seed burial, visualizing and quantifying the ability of L. terrestris to redistribute seed both vertically and horizontally throughout the soil profile. L. terrestris buried 6.5 to 17.4% of the total seeds and reduced aboveground grass biomass by 59–65 %. Vertically, L. terrestris buried seeds evenly across the 13 cm deep microcosms. Horizontally, L. terrestris aggregated seeds into small clusters aligned obliquely across soil depths, which suggest seeds being deposited in burrow walls (variance to mean ratio: 3.39 ± 2.49). Seeds were aggregated regardless of L. terrestris density but covered a greater cross-sectional area of the soil profile when more earthworms were present. Spatial patterning of shallow buried seed still capable of emergence is a newly described mechanism by which L. terrestris might influence the spatial structure of plant communities.

It is generally accepted that populations of most species experience some level of density dependence; however, this has rarely been shown for soil-dwelling invertebrate species, in particular for earthworms. Experimental data, mostly obtained at high laboratory densities, suggest intense intraspecific competition for resources and/or living space and density-dependent dynamics in earthworm populations, irrespective of their ecological group affiliation. In the present study performed in large field microcosms, I investigated whether density-dependent responses occur within the earthworm density gradients more realistic for the natural sites. Five lumbricid species from epigeic ( Dendrobaena octaedra , Lumbricus rubellus ), endogeic ( Allolobophora chlorotica , Aporrectodea caliginosa ) and anecic ( Lumbricus terrestris ) ecological groups were tested. Soil systems populated with earthworm monocultures in large (20-L) microcosms were exposed in a beech-oak forest for 4.5 months; each species was represented by two ( L. terrestris ) or three treatments forming gradients of increasing density. In two endogeic species, manifold and generally similar density-dependent responses (a retardation of growth, maturation and reproduction rates, but higher mortality rates with density increase) were revealed, likely explained by spatial competition rather than by direct food competition. In each of epigeic species density-dependent responses were less variable and more species-specific. In contrast to endogeics, direct food competition was presumably a more important cause of density-dependence. In L. terrestris no significant density-dependent responses in adult earthworms were revealed; however, they need to be further investigated in relation to the age and territorial behaviour of individual earthworms. Importantly, in any earthworm species the density variations in the reproducing generation had significant consequences for the advancing generation, affecting either the numbers or/and the size (individual weight) of the cocoons produced. It is suggested that an underestimation of density-dependent processes may cause inaccurate estimates of the activities of local lumbricid populations.

Summary Earthworm-seed interactions are increasingly recognized as ecologically important. Efforts to study these interactions make use of either no-choice or choice feeding trials due to logistical constraints or differing objectives, however, evidence is lacking regarding the consistency of feeding preferences by earthworms between these scenarios. We conducted a small-scale study in which we compared ingestion and egestion of eleven seed species by the anecic earthworm Lumbricus terrestris L. between no-choice and choice feeding dish trials. We found that seed ingestion and egestion differed between species and the seed ingestion preferences were relatively consistent (Pearson Correlation, r = 0.695) between the feeding trials. These results indicate that seeds preferred in isolation are similarly detectable and preferred alongside other options, aiding in the interpretation of results of other anecic earthworm-seed feeding experiments and suggesting that L. terrestris has a surprisingly strong ability to discriminate between and selectively consume specific seeds from a larger and diverse pool of species options.

The role earthworms play in the cycling of biochar in the soil column is poorly understood. While some studies show that earthworms favor a biochar-rich environment, they are ambiguous as to whether earthworms actively remove it and/or possibly consume it, or whether biochar indirectly provides a more favorable habitat. More importantly, associating the properties of different biochars to habitat preference by earthworms has received almost no attention. Courts were established with eight biochars from different feedstocks with varying in physicochemical properties. Circular piles (1.5 g) of biochar were applied to the surface of mesocosms containing field soil and 25 earthworms. Removal was quantified by digitally photographing the biochar samples and visually estimating disappearance over time. Most biochars were actively removed by the earthworms. The most preferred biochar was an aged biochar (>70 years) harvested from charcoal mounds, whereas the least preferred was a fast-pyrolysis biochar made from hardwood sawdust. There was an inverse relationship between the removal of biochar by earthworms and total carbon and a proportional increase with the contents of ash, Ca, Mn, and Si, although the correlations were not strong and may not explain earthworm preference. Other physicochemical properties of the biochars, such as the % volatile C, % H, porosity, and cumulative surface area, were associated with increased aerobic bacteria and fluorescent pseudomonads in soil, but not associated with biochar removal by earthworms. More research is needed to determine if tailoring specific biochars for surface removal by earthworms could be achieved by supplementing biochar with Ca, Mn, and Si and thus lead to a non-disruptive system for delivery of biochar into lower soil horizons of perennial crops. More importantly, this procedure may be useful in screening biochars for attractiveness to earthworms.

Functional relationships between belowground detritivores and/or symbionts and aboveground primary producers and their herbivores are not well studied. In a factorial greenhouse experiment we studied interactions between earthworms (addition/no addition of Lumbricus terrestris; Clitellata: Lumbricidae) and arbuscular-mycorrhizal fungi (AMF; with/without inoculation of Glomus mosseae; Glomerales: Glomeraceae) on the leguminous herb Trifolium repens (Fabales: Fabaceae) and associated plant aphids (Aphis gossypii, A. craccivora; Hemiptera: Aphidoidea). In order to be able to trace organismic interactions, earthworms were dual-labelled with stable isotopes (15N-ammonium nitrate and 13C-glucose). We specifically wanted to investigate whether (i) isotopic signals can be traced from the labelled earthworms via surface castings, plant roots and leaves to plant aphids and (ii) these compartments differ in their incorporation of stable isotopes. Our results show that the tested organismic compartments differed significantly in their 15N isotope enrichments measured seven days after the introduction of earthworms. 15N isotope incorporation was highest in casts followed by earthworm tissue, roots and leaves, with lowest 15N signature in aphids. The 13C signal in roots, leaves and aphids was similar across all treatments and is for this reason not recommendable for tracing short-term interactions over multitrophic levels. AMF symbiosis affected stable isotope incorporation differently in different subsystems: the 15N isotope signature was higher below ground (in roots) but lower above ground (leaves and aphids) in AMF-inoculated mesocosms compared to AMF-free mesocosms (significant subsystem × AMF interaction). Aphid infestation was unaffected by AMF and/or earthworms. Generally, these results demonstrate that plants utilize nutrients excreted by earthworms and incorporate these nutrients into their roots, leaf tissue and phloem sap from where aphids suck. Hence, these results show that earthworms and plant aphids are functionally interlinked. Further, 15N-labelling earthworms may represent a promising tool to investigate nutrient uptake by plants and consequences for belowground-aboveground multitrophic interactions.

Large sized biopores (diameter >2 mm) in the subsoil can be created by tap roots, which leave voids after their decay, or by the burrowing activity of anecic earthworms which may benefit from the temporary lack in tillage in perennial cropping systems. However, the interactions between root growth and earthworm activity in the process of biopore formation during perennial ley cropping are not well understood. The aim of this field study was to quantify the development of the abundance of the anecic earthworm Lumbricus terrestris and the biopore density during the cultivation of lucerne ( Medicago sativa L.), chicory ( Cichorium intybus L.) and tall fescue ( Festuca arundinacea Schreb.) grown for either one, two or three years. An increased abundance of L. terrestris was already recorded after two years of continuous ley when compared with one year cultivation. The ley crop species had only minor influence on the abundance of L. terrestris . Biopore densities of both diameter classes under study (2–5 mm and >5 mm) were not significantly affected by the duration of ley cropping. In contrast, biopore densities were influenced by ley crop species. More biopores of diameter class 2–5 mm were recorded after chicory than after fescue. Lucerne cropping resulted in intermediate biopore density. Additionally, in an incubation experiment under field conditions, we quantified whether L. terrestris preferentially created new biopores or colonized abandoned, previously existing ones. After three weeks of incubation, one third of the adult individuals incubated in the experimental area created new biopores at 0.4 m soil depth. A similar percentage of individuals colonized previously existing biopores, partially widening the lumen of smaller sized biopores. The remaining individuals remained in the topsoil. Sub-adult individuals rarely formed new pores. Half of the introduced sub-adults remained in the topsoil. We conclude that in crop rotations new biopores can be generated during perennial ley cropping by taproot systems of ley crops, but that a two to three- year period without tillage is not sufficient for populations of anecic earthworms to make a marked contribution to biopore density in the subsoil. The relevance of anecic earthworms for altering physical and chemical properties of biopores during ley cropping still needs further investigation.

Through their manipulation of soil physical and chemical properties, earthworms have the potential to increase nutrient mineralization and benefit crop production. However, this effect is dependent on numerous factors including earthworm densities and ecological strategies. In addition to impacting density, soil environmental conditions may limit earthworm activity to specific times during the growing season, moderating their effects on nutrient availability and crop growth. The purpose of this study was to determine the active period of earthworms to better assess their potential impact on crop productivity in dryland wheat production systems in the Palouse region of northern Idaho and eastern Washington, U.S.A. Earthworm community density, age structure, diversity, and soil moisture and soil temperature were monitored over a 14-month (April 2014–June 2015) period in six dryland wheat fields. All earthworms collected were exotic species, with the endogeic species, Aporrectodea trapezoides being predominant at all sites (87% of all adults identified). Allolobophora chlorotica, Lumbricus terrestris and Aporrectodea tuberculata were collected at lower frequencies (1.8–6.4% of adults). Mean densities ranged from 14 to 75 individuals m−2, and populations transitioned to aestivation beginning in mid-June of both years. All earthworms were active (no aestivating individuals) on 56.9% of the sampling dates in 2014 and 71% of the days in 2015. A short active period and average densities at most sites of less than 100 individuals per m2 suggest that the impact of earthworms on crop growth may be limited in conventional, dryland agricultural fields of this region.

A microcosm experiment was performed to investigate the effects of post-harvest potato tubers from transgenic cyanophycin-producing potatoes on Lumbricus terrestris (L.) activity and biomass, number of cocoons and their hatchability as well as the remaining cyanophycin content in soil and cast samples during a period of 80 days. Potato tubers from four transgenic potato events with different cyanophycin content in a range from 0.8 to 7.5% were compared to the near isogenic, non-transgenic control ( Solanum tuberosum L. cv. Albatros) and a comparative potato cultivar ( S. tuberosum L. cv. Desiree). One treatment with transgenic tuber residue but without earthworms was prepared as an additional control. Potato tuber loss from the surface of the microcosms was significantly higher in the treatments with transgenic potato tubers compared with non-transgenic treatments. It can be estimated that the earthworm contribution to potato tuber loss from the soil surface was approximately 61%. Mean number of cocoons in addition to the number of hatched cocoons varied from 2.6 to 6.2 and from 7 to 15 accounting for 45.2–83.35% hatchability, respectively, but no significant differences between the treatments were found. The same was true for the development of earthworm biomass in the various treatments. The cyanophycin content in soil samples was significantly higher when earthworms were present indicating that the cyanophycin content in the upper soil layer might have been enhanced through earthworm burrowing activity. Overall, it is concluded that tubers from transgenic cyanophycin potatoes are easily degradable and neither inhibit nor stimulate earthworm growth, reproduction, and activity.

Two laboratory experiments were carried out to determine the potential effects of lime application on the behavior of earthworms inoculated in an acidified forest soil from Vosges Mountains. Several field soils were studied: (i) a non-limed soil that had received decades of atmospheric acid depositions ( pH H 2 O = 3.9 ) , (ii) an in situ limed soil that had been limed 6 years before at 2.5 t ha −1 ( pH H 2 O = 4.2 ) and (iii) in vitro limed soils composed of non-limed soil mixed with several lime amounts in the laboratory corresponding to field rates of 1, 2.5, 5, 10 and 20 t ha −1 . Firstly, we adapted the earthworm avoidance test ( ISO, 2006 ) by using Eisenia fetida as the model organism and Lumbricus castaneus , a local species, to determine earthworm preference between non-limed and limed soils. Secondly, a cast production (CP) study was performed according to Capowiez et al. (2009) with Lumbricus terrestris , in seven different treatments (non-limed soil, in situ limed and five in vitro limed soils with pH from 5 to 6.3). Both species avoided the non-limed soil in favour of in situ and in vitro limed soils for both species. Results of the CP bioassay showed that the bioturbation behavior of L. terrestris significantly increased with the increase of soil pH, following a dose–response curve. However, in the long term (>6 years), the application of lime was insufficient to significantly improve soil conditions for enhancing earthworm activity. In conclusion, we may recommend this kind of earthworm laboratory tests with field soils to assess any changes in soil quality over time due to liming application.

Some of the widely used cover crops in temperate agroecosystems (including species of the Brassicaceae and Poaceae) have been shown to exhibit allelopathic effects. In particular, various Brassicaceae have been reported to act as biofumigants against a variety of soil-borne pests through the release of i.a. isothiocyanates (ITC) from glucosinolate precursors. Although these allelochemicals may potentially reduce the need for application of synthetic pesticides, their effects on beneficial soil ecosystem engineers such as earthworms (Lumbricidae) have not been assessed yet. Food choice chambers were used to assess short-term food preferences of Lumbricus terrestris L. for lacy phacelia ( Phacelia tanacetifolia BENTH.), the Poaceae Italian ryegrass ( Lolium multiflorum LAM.) and oats ( Avena sativa L.), and the Brassicaceae yellow mustard ( Sinapis alba L.) and rapeseed ( Brassica napus L.) while litter bags were used to study long-term litter preference under field conditions. Habitat preference of L. terrestris was determined through simple habitat preference units. Ryegrass residues were a preferred food resource, both in fresh and partly decomposed state, over mustard, phacelia or rapeseed residues, and these were in turn more fed on than oats. Litter disappeared at a fast and variable rate from litter bags under field conditions. No clear relationships with residue C:N ratio were observed. Habitats in which living oat plants were present were avoided in comparison to habitats with bare soil or yellow mustard plants. In conclusion, brassicaceous cover crops are not preferred nor avoided by L. terrestris compared to the other cover crops in this study. Decreased ITC release and earthworm exposure under field conditions may further lower the risk of harmful effects, but further research on the long-term impact is needed.

In Central Europe a rich endemic earthworm fauna exists. The ecology of most of these species has not been studied. In laboratory mesocosms we examined leaf litter acceptance and cast deposition of a total of 30 species, 21 of which were endemic. In both experiments earthworms, especially small species, exhibited a variety of behaviors. Hornbeam litter was consumed at higher C/N values by anecic species, but some epigeics still did not accept it. Surface cast deposition varied between 0 and 100% among small endogeics. Most anecic species deposited their casts belowground, but the model anecic species, Lumbricus terrestris was an exception: 79% of its total cast was deposited on the surface. Epigeics and endogeics did not clearly separate in these behavioral traits. Refinement of ecological categorization of Lumbricidae needs to include data on lesser known species.

To study the feasibility of earthworm introduction for increasing the macroporosity and permeability of arable heavy clay, deep-burrowing earthworms ( Lumbricus terrestris L.) were inoculated into a tile drained experimental field in Jokioinen, S-W Finland in autumn 1996. Inoculation with the Earthworm Inoculation Unit technique was at the up-slope end of the field, in the field margins under permanent grass, and inside the four 0.46 ha plots of the field. The experiment was monitored on three occasions. In 1998 the L. terrestris population had persisted in low numbers only in field and plot margins. By 2003, when the field had been under set-aside grass for three years, density had grown in the margins and L. terrestris were also found inside the field at a very low density. The third monitoring was in autumn 2009, after a further four years as set-aside and a subsequent division of the field into no-till and ploughing management, and looked at the effects of management (margins, no-till, ploughing), distance from the inoculation and sub-drainage on L. terrestris abundance. The abundance displayed a clear gradient over the field, declining from 14 ind. and 18 g m −2 at 5–9 m from inoculation, to 1 ind. and 2 g m −2 at 56–60 m distance. Margins had the highest abundances (16 ind. and 32 g m −2 ), followed by no-till (4 ind. and 4 g m −2 ) and ploughing (1 ind. and 1 g m −2 ). Abundances were significantly higher above the tiles than between them ( P

Research on earthworms in North America has focused on the effects of invasive earthworms, with few studies examining the ecology of native earthworm species. Deer have been shown to influence belowground processes through grazing, trampling, and fecal pellet deposition. We proposed that native earthworms in an oak-dominated forest in Virginia might benefit from increased organic matter provided by deer fecal material. We examined potential interactions between a common aboveground herbivore, the white-tailed deer (Odocoileus virginianus), and earthworms using laboratory and field experiments. In our laboratory experiment, we found that a native earthworm, Eisenoides carolinensis, and an invasive earthworm, Lumbricus terrestris both fared better in treatments with deer pellets compared with the treatment with leaf litter alone. In our field experiment, we used fences to exclude deer from six plots and left twelve plots unfenced to explore the effects of deer activity on earthworm biomass and density. We also examined the effects of deer on soil and vegetation characteristics. After three years, the amount of herbaceous cover was higher on fenced plots compared with unfenced plots. Although we found no other differences for vegetation and soil characteristics between fenced and unfenced plots, many of these variables were important as covariates in our models examining the effect of deer exclusion on earthworms, indicating plot-level (as opposed to treatment-level) variation in these variables. All identifiable earthworms were either E. carolinensis or Diplocardia spp. (both native species), with E. carolinensis making up 90% of the specimens. The total biomass of earthworms, as well as the biomass and density of adult and small juvenile earthworms, was greater on unfenced plots with deer activity compared with fenced plots. This study highlights the importance of above- and below-ground interactions in forest ecosystems by showing that E. carolinensis appears to benefit from the presence of deer and adds to our sparse knowledge of the ecology of this native earthworm.

Earthworms secrete granules of calcium carbonate. These are potentially important in soil biogeochemical cycles and are routinely recorded in archaeological studies of Quaternary soils. Production rates of calcium carbonate granules by the earthworm Lumbricus terrestris L. were determined over 27 days in a range of soils with differing chemical properties (pH, organic matter content, water holding capacity, bulk composition, cation exchange capacity and exchangeable cations). Production rate varied between soils, lay in the range 0 – 0.043 mmol CaCO 3 (0–4.3 mg) earthworm−1 d−1 with an average rate of 8 × 10 − 3 mmol CaCO 3 (0.8 mg) earthworm−1 d−1 and was significantly correlated (r = 0.68, P ≤ 0.01) with soil pH. In a second experiment lasting 315 days earthworms repeatedly (over periods of 39–57 days) produced comparable masses of granules. Converting individual earthworm granule production rates into fluxes expressed on a per hectare of land per year basis depends heavily on estimates of earthworm numbers. Using values of 10–20 L. terrestris m−2 suggests a rate of 18 – 3139 mol CaCO 3 ha − 1 yr − 1 . Data obtained from flow-through dissolution experiments suggest that at near neutral pH, granule geometric surface area-normalised dissolution rates are similar to those for other biogenic and inorganic calcites. Fits of the data to the dissolution relationship r = k(1 − Ω)n where r = dissolution rate, k = a rate constant, Ω = relative saturation and n = the reaction order gave values of k = 1.72 × 10−10 mol cm−2 s−1 and n = 1.8 for the geometric surface area-normalised rates and k = 3.51 × 10−13 mol cm−2 s−1 and n = 1.8 for the BET surface area-normalised rates. In 196 day leaching column experiments trends in granule dissolution rate referenced to soil chemistry corresponded to predictions made by the SLIM model for dissolution of limestone in soil. If soil solution approaches saturation with respect to calcium carbonate, granule dissolution will slow or even stop and granules be preserved indefinitely. Granules have the potential to be a small but significant component of the biogeochemical cycling of C and Ca in soil.

Earthworms were shown to significantly affect seeds and seedlings survival via their ingestion and digestion for nutritive purposes. Such selective feeding of earthworms on plant seeds is likely to favour certain plant species and to affect seed bank composition, plant recruitment and plant community structure. Relationships between earthworms and seeds, particularly seed traits that determine attractiveness of seeds for earthworms, are yet to be determined. In this study, the influence of six seed traits was tested on the ingestion, digestion and germination of seeds by two earthworm species ( Lumbricus terrestris , anecic and Satchellius mammalis , epigeic). The seed traits tested were their length, width, weight, shape, oil content and the presence of trichomes on their surface. Each earthworm species was introduced into a microcosm with eleven seed species from a chalk grassland that represented those different traits. Ingested, digested and germinated seeds were counted after voiding the guts of the earthworms. Univariate and multivariate analyses showed that seed length, width, weight and seed oil content could significantly affect the ingestion of seeds for both earthworm species. Seed width and seed oil content were the two traits that influenced the digestion of seeds the most, but only for L. terrestris . We also found that seed ingestion was earthworm species-specific but we found no correlation between earthworm traits and number of ingested or digested seeds. Few seeds germinated from L. terrestris casts and no seeds germinated from S. mammalis casts. Implications in terms of plant evolution strategies are further discussed.

We have shown previously that riboflavin is stored in chloragosomes of chloragocyte-derived earthworm eleocytes what may have an adaptive value for worms vulnerable to soil-derived pathogen invasion. Thus, it is important to determine whether riboflavin stores are also present in earthworm species with low eleocyte counts, especially in the chloragocytes of their chloragogen tissue that surrounds the coelomic site of the intestine, and find out its putative roles in earthworm immunity. Experiments were performed on adult worms from 6 species. Freely floating coelomocytes (consisting of amoebocytes plus species-specific numbers of eleocytes) were extruded by mild electric shock and then chloragocytes from the same anaesthetized worm were mechanically detached into buffer. Both cell suspensions were analyzed by spectrofluorometry for riboflavin content. It turned out that riboflavin is stored in species-specific quantities in all investigated species. Riboflavin storage predominates in free coelomocytes of eleocyte-rich species (Eisenia andrei, Dendrobaena veneta, Allolobophora chlorotica) while in chloragocytes of species with few eleocytes (Lumbricus terrestris, L. rubellus, and Aporrectodea caliginosa). Upon a massive microbial impact, the coelomocytes (both amoebocytes and eleocytes) are involved in the formation of multicellular bodies encapsulating soil-derived pathogens, what is connected with enhanced coelomocyte mobility. Thus the second aim of the present investigation was to check if riboflavin can participate in coelomocyte accumulations. Tests performed in a 48-well chemotaxis chamber revealed that riboflavin behave as chemoattractant for coelomocytes of all investigated earthworm species, which may be one of mechanisms underpinning its immunomodulatory functions.

The aim of this study was to test the impact of compost and biochar, with or without earthworms, on the mobility and availability of metals, and on the growth of grass to re-vegetate contaminated soil from the Parys Mountain mining site, Anglesey. We also determined if the addition of earthworms compromises remediation efforts. In a laboratory experiment, contaminated soil (1343 mg Cu kg −1 , 2511 mg Pb kg −1 and 262 mg Zn kg −1 ) was remediated with compost and/or biochar. After 77 days Lumbricus terrestris L. earthworms were added to the treatment remediated with both compost and biochar, and left for 28 days. L. terrestris was not able to survive in the biochar, compost or unamended treatments. A germination and growth bioassay, using Agrostis capillaris (Common Bent) was then run on all treatments for 28 days. The combination of biochar and compost decreased water soluble Cu (from 5.6 to 0.2 mg kg −1 ), Pb (from 0.17 to less than 0.007 mg kg −1 ) and Zn (from 3.3 to 0.05 mg kg −1 ) in the contaminated soil and increased the pH from 2.7 to 6.6. The addition of L. terrestris to this treatment had no effect on the concentration of the water soluble metals in the remediated soil. The compost was the only treatment that resulted in germination and growth of A. capillaris suitable for re-vegetation purposes. However, the combination of compost and biochar (with or without L. terrestris ) produced the lowest concentrations of Cu (8 mg kg −1 ) and Zn (36 mg kg −1 ) in the aboveground biomass, lower than the compost treatment (15 mg Cu kg −1 and 126 mg Zn kg −1 ). The addition of biochar and compost both separately and as co-amendments was effective in reducing the mobility and availability of metals. The addition of L. terrestris did not re-mobilise previously sequestered metals.

Earthworms have been shown to influence plant growth, survival and fecundity. They can therefore affect plant demography in plant communities changing their composition. A long term mesocosm experiment was set-up to test the effects of an endogeic (Aporrectodea caliginosa) and an anecic (Lumbricus terrestris) earthworm species on assemblages of four species of annuals: one grass (Poa annua), two forbs (Veronica persica and Cerastium glomeratum) and one legume (Trifolium dubium). The number of individuals and the biomass of each species were investigated. A. caliginosa and L. terrestris affected the density of T. dubium at each of the three monitored census dates. The other plant species responded to A. caliginosa and L. terrestris at the second and third generations. The presences of A. caliginosa and L. terrestris reduced the total number of plant individuals from the second to the third generation. At harvest (3rd generation), T. dubium and V. persica had more and larger individuals in the presence of A. caliginosa. When both earthworm species were present, T. dubium had few but larger individuals. Our study confirms that earthworms affect plant demography and plant community structure. Our results also show that accurate prediction of long-term effects of earthworms on plant communities cannot be achieved using results on their short-term effects on plant growth. This is due to the poor understanding of the effects of earthworms on plant resource allocation and demography, and also the possibility that earthworms may exert the opposite effect on the short and long-term availability of nutrients.

Currently, the driving factors of active earthworm dispersal across the soil surface are not sufficiently understood, and distances traversed by individual earthworms have rarely been quantified. Research progress has been hampered by the lack of adequate observation methods as well as fast, objective and quantitative measurements of nocturnal earthworm behaviour. In this work, we report on the potential of a new, automated method using infrared-sensitive webcams and computer image analysis. Nightly surface activities of Lumbricus terrestris L. were monitored quantitatively while manipulating levels of disturbance, burrow availability and congener presence in standard observation units. The automated observation system proved to be simple and inexpensive to build, provided reliable quantitative measures of locomotive behaviour without animal disturbance, and considerably reduced human workload and bias. Waterlogging of the burrow zone stimulated surface activities around and away from the home burrow as compared to habitat disturbance by pesticide application and vibration. However, dispersing earthworms never settled in prefabricated burrows. Surface activity of individuals subjected to waterlogged conditions was influenced by the availability of alternative habitat. Minimal habitat disturbance (vibration) and the presence of conspecific individuals resulted in an increased amount of burrow-anchored, possibly sexually oriented, behaviour, but reciprocal burrow visits and mating were not observed. Pesticide application did not result in dispersal, increased foraging activities or sexual attraction attempts during this short-term study. The presence, extent and mechanisms of the remote assessment of important cues in the surroundings of the home burrow by L. terrestris need further research. Infrared monitoring opens new research avenues of earthworm surface behaviour studies (e.g. density-dependent dispersal, habitat selection, (re)colonization, invasion).

Summary Earthworms play an important role in organic matter processing and nutrient cycling in temperate ecosystems. It is known that earthworms preferentially ingest sand grains mixed with organic material and it has been suggested that the mixture of sand and organic material during the gut passage may play an important role in litter degradation and nutrient release, which may accelerate assimilation of nutrients by earthworms and likely enhance plant growth. In a greenhouse experiment, we investigated the effect of the anecic earthworm species Lumbricus terrestris and the endogeic earthworm species Octolasion tyrtaeum separately and in combination on carbon and nitrogen mobilisation from surface applied rye litter labelled with 13 C and 15 N. By mixing arable soil with 25% sand, we investigated the effect of the availability of sand. To quantify the mobilisation of 15 N, three rye seedlings were planted in each microcosm and analysed for isotope signature after 3 months of incubation. Mobilisation of 13 C was quantified by analysing the incorporation of label into the soil and earthworm tissue. Irrespective of the addition of sand the biomass of L. terrestris decreased during the experiment, whereas that of O. tyrtaeum increased in single species treatment and slightly decreased in the combined treatment with L. terrestris . The concentration of 13 C decreased while that of 15 N increased in the tissue of both earthworm species, with the effect being more pronounced in L. terrestris for 13 C and in O. tyrtaeum for 15 N. Both earthworm species increased shoot biomass, with the effect of L. terrestris (+80%) exceeding that of O. tyrtaeum (+28%) and maximum plant biomass in the combined treatment (+92%). Earthworms did not affect the 15 N concentration of rye plants, but sand significantly increased 15 N concentration of plants, presumably due to improving soil structure. Overall, the incorporation of 13 C into the soil was low and was significantly increased in presence of sand, with the highest enrichment in treatments without earthworms. The results indicate that the availability of sand does not increase effects of earthworms on litter degradation, nutrient release and plant growth. Rather, independent of soil sand content earthworms increase plant growth, whereas the presence of sand itself enhances the uptake of nitrogen from plant litter and the incorporation of litter carbon into the soil.

Summary The soil seed bank functions to escape unfavourable environmental conditions and seed predation. Anecic earthworms are increasingly recognised as important dispersers and predators of plant seeds. In contrast, the role of the usually more abundant endogeic earthworms which live and feed in the soil on plant seeds is largely unknown. We tested whether (A) endogeic earthworms ( Aporrectodea rosea , Allolobophora chlorotica , Octolasion tyrtaeum , Aporrectodea caliginosa ) ingest and digest grassland plant seeds ( Phleum pratense , Bellis perennis , Trifolium repens , Poa trivialis , Plantago lanceolata , Medicago varia ), (B) the passage of seeds through the gut of endogeic earthworms modifies seed germination, and (C) excreta (mucus and casts) of endogeic earthworms modify seed germination. As a reference effects of the well-studied anecic species Lumbricus terrestris were determined. Endogeic earthworms ingested and digested all of the studied plant seeds; however, both ingestion and digestion were earthworm and plant species specific. Moreover, passage through the gut of endogeic earthworms and their excreta modified plant seed germination (gut passage: B. perennis ; excreta: Ph. pratense and Pl. lanceolata ). The results indicate that endogeic earthworms may strongly impact the composition of the soil seed bank and, consequently, plant community assembly via direct and indirect effects on plant seeds. Since post-dispersal seed predation is a key factor for the structure of plant communities, with the effect on seed survival potentially exceeding that of pre-dispersal predation, seed predation and changes in germination of seeds by endogeic earthworm species is likely to drive plant community composition.

Summary The basic ecology of well-researched earthworm species, such as Lumbricus terrestris, remains relatively unknown. In order to contribute to the limited body of knowledge, the present work aimed to investigate if specific behaviours could be detected between an adult and the cocoons it produced by comparison with a non-parental adult and cocoons. Modified Evans’ boxes (0.8×0.2×0.008 m) with recently mated adults allowed observation of their habits under what was essentially a 2-D system. Experimental manipulation (at 81 days) involved four treatments: (1) L. terrestris removal (LtRm); (2) L. terrestris replacement (LtRp), where individuals were replaced by others; (3) control, with no manipulation and (4) L. terrestris removal control (CLtRm) where individuals were removed and then reintroduced in the same box, to account for any effects of the removal method. Burrowing patterns of adults and later, hatchlings, were recorded throughout the duration of the experiment (191 days). Cocoon production across treatments did not differ significantly ( p >0.05) and averaged 26±6.4 cocoons worm −1 over a 26 week period. In the LtRm treatment mean cocoon production was 12.6±2.7 cocoons worm −1 over 11 weeks. Forty one percent of cocoons were deposited in the upper 0.05 m of the soil profile. Cocoons below that depth were found deposited in side burrows (1–4 cm in length) and were coated with earthworm casts. Hatchling number and survival rate did not differ significantly across treatments ( p >0.05) with means±s.d. of 2±2.2 and 62±29%, respectively. Hatchling mass in the LtRm treatment (0.4±0.38 g), was found to be significantly greater ( p

Summary Earthworm burrows contribute to soil macroporosity and support diverse microbial communities. It is not well known how fluctuations in soil temperature and moisture affect the burrowing activities of earthworms. The objective of this experiment was to evaluate the maximum depth and length of burrows created by the endogeic earthworm Aporrectodea caliginosa (Savigny) and the anecic earthworm Lumbricus terrestris L. for a range of temperatures (5–20 °C) and soil water potentials (−5 and −11 kPa). The laboratory microcosm was a plexiglass chamber (45 cm high, 45 cm wide) containing 0.14 m 2 of pre-moistened soil and litter, designed to house a single earthworm for 7 days. Earthworm mass, surface casting and burrowing activities were affected significantly by soil temperature, moisture and the temperature×moisture interaction. Burrow length and maximum burrow depth increased with increasing temperature, but there was less burrowing in wetter soil (−5 kPa) than drier soil (−11 kPa). Weight gain and surface casting, however, were greater in soil at −5 kPa than −11 kPa. Our results suggest more intensive feeding and limited burrowing in wetter soil than drier soil. Earthworms inhabiting the non-compacted, drier soil may have pushed aside particles without ingesting them to create burrows. The result was that earthworms explored a larger volume of soil, deeper in the chamber, when the soil was drier. How these burrowing activities may affect the community structure and activity of soil microorganisms and microfauna in the drilosphere remains to be determined.

Summary Earthworms are being used as bio-indicators to assess terrestrial pollution. However, it is often not known whether their populations possess a uniform genetic structure, which would allow comparison of residues or biological properties of earthworms from different sampling locations. In order to investigate this point, random amplified polymorphic DNA (RAPD) variation was surveyed in earthworms ( Lumbricus terrestris ) from five different sampling sites in Germany. Forty oligonucleotide RAPD primers (10 base pairs in length) were screened, three of which produced high polymorphic band patterns. A total of 61 DNA fragments were detected in 90 individuals of L. terrestris from five sampling sites with 49 (80.3%) RAPD markers being polymorphic. The genetic similarities within (band sharing rates between 0.756 and 0.795) and among the L. terrestris populations (0.635) were similar even at widely separate locations. Inter-population variation in the RAPD pattern for all five earthworm populations accounted for 37.9% of the total variation, while intra-population variation for three adjacent Saarland populations accounted for only 18.0% of the total variation. Principal component analysis (PCA) and the genetic distances of the populations confirm these results. Twenty-four percent of the genetic distance is caused by geographical isolation as shown by a test for isolation by distance. These results show that L. terrestris fulfils the genetic qualifications for a bio-indicator particularly at closely located sampling sites. However, the results also suggest that earthworm studies of widely separated locations should include genetic characterisation of the earthworm samples.

Summary Knowledge of the effects of species diversity within taxonomic groups on nutrient cycling is important for understanding the role of soil biota in sustainable agriculture. We hypothesized that earthworm species specifically affect nitrogen mineralization, characteristically for their ecological group classifications, and that earthworm species interactions would affect mineralization through competition and facilitation effects. A mesocosm experiment was conducted to investigate the effect of three earthworm species, representative of different ecological groups (epigeic: Lumbricus rubellus; endogeic: Aporrectodea caliginosa tuberculata; and anecic: Lumbricus terrestris), and their interactions on the bacterial community, and on nitrogen mineralization from 15N-labelled crop residue and from soil organic matter. Our results indicate that L. rubellus and L. terrestris enhanced mineralization of the applied crop residue whereas A. caliginosa had no effect. On the other hand, L. rubellus and A. caliginosa enhanced mineralization of the soil organic matter, whereas L. terrestris had no effect. The interactions between different earthworm species affected the bacterial community and the net mineralization of soil organic matter. The two-species interactions between L. rubellus and A. caliginosa, and L. rubellus and L. terrestris, resulted in reduced mineral N concentrations derived from soil organic matter, probably through increased immobilization in the bacterial biomass. In contrast, the interaction between A. caliginosa and L. terrestris resulted in increased bacterial growth rate and reduced total soil C. When all three species were combined, the interaction between A. caliginosa and L. terrestris was dominant. We conclude that the effects of earthworms on nitrogen mineralization depend on the ecological traits of the earthworm species present, and can be modified by species interactions. Knowledge of these effects can be made useful in the prevention of nutrient losses and increased soil fertility in agricultural systems, that typically have a low earthworm diversity.

Summary Developments in ecotoxicology and soil restoration have led to an increase in earthworm research over the past 20 years. Rearing of earthworms under laboratory conditions has therefore become desirable, but perceived difficulties have beset this practice. A review of recent research on the development of earthworm culture techniques for temperate, soil dwelling (anecic and endogeic) species is presented. Critical abiotic and biotic factors including soil moisture, organic matter, temperature, pH, earthworm density and species composition are considered, and optimal values provided for four species ( Allolobophora chlorotica, Aporrectodea caliginosa, Aporrectodea longa and Lumbricus terrestris ). Published figures relating to growth to maturity, cocoon production and cocoon viability, for these frequently studied species are collated and advice offered for culture of other soil dwelling species.

Earthworms dominate the animal biomass in moist floodplain soils. They are known to survive long periods in aerated water, but little is known about earthworm population dynamics in floodplain systems with changing inundation frequencies. This study determined earthworm population dynamics in a floodplain system, in relation to frequency and duration of flooding events. From October 2000 to May 2003 earthworms were hand sorted in the 'Afferdensche en Deestsche Waarden', a floodplain on the south bank of the river Rhine, near Druten, The Netherlands. Earthworm numbers and biomasses per age class (adult, subadult, juvenile) were recorded. Numbers and biomasses tend to decrease during flooding. Lumbricus terrestris was found in high numbers (>10/m2) only at the end of a flooding period. Allolobophora chlorotica was hardly affected by flooding; their biomass remained stable during the year. Aporrectodea caliginosa showed fluctuating numbers and biomasses during the sampling period that did not correlate with flooding frequency. Numbers and biomasses of Lumbricus rubellus were strongly reduced at the end of each flooding event, but their population densities fully recovered until next flooding event. Earthworm populations in floodplains fluctuate in time, depending on the season and on the time, duration and frequency of flooding. Different earthworm species react differently towards these flooding dynamics. © 2004 Elsevier GmbH. All rights reserved.

A laboratory experiment was carried out to test the hypothesis that the earthworms Lumbricus terrestris and Aporrectodea caliginosa are able to maintain their populations and reproduce in the acid forest soil of a deciduous forest where no lumbricids were found in the field. The experiment was conducted in 45-l containers in which layers of mineral subsoil, humus and organic topsoil collected from the site were established. Both species survived and at least L. terrestris reproduced during the 60 weeks’ incubation. Burrows and middens of L. terrestris were recorded and quantities of litter were consumed. The presence of lumbricids increased the organic matter content of humus, reduced the acidity of the topsoil and humus layers, and suppressed the population of the enchytraeid Cognettia sphagnetorum. A dense population of Enchytraeus albidus was found in L. terrestris middens. It is concluded that edaphic factors do not explain the absence of earthworms, but isolation from cultural landscapes and lack of opportunity to colonize the site from the surroundings is the decisive factor.

Summary We investigated whether exposure to UV-B results in biochemical changes in leaf litter, affecting growth rates of earthworms feeding on this litter and cast chemistry. Seedlings of Betula pubescens L. were grown under zero and ambient UV-B (at 52 °N) regimes under optimal conditions. Following three months exposure, plants were allowed to senesce and leaf litter was collected. Lumbricus terrestris and Lumbricus rubellus were offered three substrates – processed oat grain, zero UV-B leaf litter and ambient UV-B leaf litter. Fourier transform infrared spectroscopy (FT-IR) analyses indicated that these substrates differed markedly in their composition, showing separation according to UV-B treatment and oat grain. There were no significant effects of UV-B treatment on the mass of earthworms feeding on litter, although trends suggested that L. rubellus benefited from the UV-B treated litter whilst L. terrestris showed the converse response. FT-IR analyses of L. terrestris casts showed more consistent differences in their biochemistry than was the case for litter. UV-B induced changes in living leaf material introduced to soil, even after earthworm processing, may have implications for cast microbial communities and nutrient cycling.

Summary The morphology of Lumbricus terrestris L. burrows was investigated in relation to subsurface tile drain position. The aim was to clarify the causes and consequences of higher densities of L. terrestris previously measured above the tiles at the study site. At two pairs of study pits, the plough layer was removed from a 1 m × 2 m area above the tile and at 8 m distance from it. Burrows of L. terrestris were identified at the plough pan, resident worms removed and burrows cast with dyed fibreglass resin. The resin casts were exposed in the profile, depth and length of casts measured and their connections with tiles recorded. In both above-tile pits, two cases were recorded where the cast burrow ended at the tile surface. These contacts indicate the potential importance of burrows in the conduction of water and solutes from the soil surface layers into the tiles. The mean depth of burrows was 1.0 m (se = 0.024, n = 27) above the tiles and 0.83 m (se = 0.036, n = 12) between the tiles. During adverse soil conditions such as droughts, individuals living near the tiles may gain from the shelter provided by their deeper burrows and this could partly explain the higher population densities above the tiles.

Summary Large anecic earthworms Lumbricus terrestris create distinctive microhabitats called middens, which strongly affect the spatial distribution of litter and litter-dwelling animals on the soil surface. The community of filamentous microscopic fungi was analysed in L. terrestris middens and control samples using the washing and plating technique. Four substrates were analysed: mineral soil, control litter, litter from L. terrestris middens, and L. terrestris casts from the middens. The composition of microfungal communities in studied substrates was compared using multidimensional scaling and discriminant analysis. No difference was found between dominance structure of fungal communities in control litter and litter from earthworm middens. In both types of litter the most frequent fungi were Alternaria alternata, Cladosporium herbarum and C. cladosporioides . In contrast, the fungal community in L. terrestris casts strongly differed from those in soil and both litter types (P Trichosporiella hyalina, Humicola grisea and Monilia sp., which were much less abundant in soil and litter. It is concluded that at a given spatial scale the feeding activity of L. terrestris has a larger impact on the community of filamentous fungi in the litter layer than the creation of favourable microhabitats for specialized fungivorous animals like collembolans.

Summary The complex and dynamic nature of soil makes the assessment of soil biodiversity difficult. Findings presented here form part of a wider scheme to develop ‘bio-sampling’ methods based on earthworm cast analysis. Our overall aim is to achieve high throughput, metabolic procedures to monitor soil biological activity and, in particular, to investigate the potential for gene transfer from plants to soil micro-organisms and its consequences. Here experiments were carried out to assess several potential foods (oat grain, fresh and aged tobacco) for Lumbricus terrestris and Lumbricus rubellus , species being considered for later experimentation. These experiments provided temporal microbial composition and activity data in ageing casts, an environment where gene transfer might occur. For both earthworm species, there was a predictable microbial succession (from bacteria to fungi) as casts aged. Species also differed in their cast microbiology in response to food type, but less so with more processed food. Analysis of ageing casts by FT-IR spectroscopy coupled with cluster analysis indicated greater chemical changes in casts of L. terrestris than for L. rubellus , regardless of food type.

Summary Coelomocytes (extruded via dorsal pores of earthworms subjected to 5V electric shock) of adult Allolobophora chlorotica, Lumbricus terrestris, Dendrobaena veneta and Eisenia fetida consisted of species-specific proportions of hyaline amoebocytes, granular amoebocytes, and eleocytes. In all species a significant increase of granular amoebocytes with a parallel decrease of hyaline amoebocytes was recorded by the end of Spring and beginning of Summer, both in animals from the natural environment and in those kept in the laboratory at the room temperature. It indicates that coelomocyte proliferation/maturation is dependent mainly on the annual endogenous rhythm, which is relatively stable even at atypical ambient temperatures. During four successive seasons viability and functions (plastic adherence or neutral red pinocytosis) were recorded in coelomocytes of A. chlorotica assayed at various in vitro temperatures. In coelomocytes retrieved from animals freshly collected from their natural environment, coelomocyte activity was better at low temperatures (0 °C and 10 °C) during the Winter, while during other seasons (especially in the Summer) it was best at 22 °C. Such seasonal effects were abolished in coelomocytes from animals tested after one-month acclimation to the room temperature, as in all seasons cell functions were best at 22 °C. These observations indicate that earthworm coelomocytes can thermally adapt. This phenomenon was also recorded in L. terrestris, D. veneta and E. fetida . In conclusion, earthworm coelomocyte proliferation/maturation seems to be endogenously controlled while coelomocyte activity seems to be more plastic and subjected to thermal adaptation.

Summary A mixed stand of red oak (Quercus rubra) and common beech (Fagus sylvatica) on a compacted and acidified sandy loam soil was harvested and reforested with ash (Fraxinus excelsior) in 1992. The ecosystem restoration trial in this newly established ash plantation included 180 trees and was set up in a block design with 4 blocks, 3 experimental groups per block and 15 trees per experimental group. Experimental groups were: (1) application of P, K, Ca and Mg fertiliser to the planting pit; (2) combined application of fertiliser and earthworms to the planting pit; and (3) a control without additional restoration measures. Fertiliser application consisted of 500g dolomite, 100g Thomas slags and 100g kieserite; earthworm introduction consisted of 40 individuals, being 20 anecics (Lumbricus terrestris L. and Nicodrilus longus Ude) and 20 endogeics (Aporrectodea caliginosa Sav., Aporrectodea rosea Sav. and Allolobophora limicola Michaelsen). Tree growth was monitored annually. The control trees failed to grow and died after two years. Excellent growth was found for treated trees, and treatment-related growth patterns were observed: fertilised trees grew faster than fertilised trees with earthworms during the first two years, with the trend reversed from year 4 onwards. Although this trend suggested that introduced earthworms provided a more sustained response to fertiliser, this was not conclusively confirmed by an evaluation of 24 trees 10 years after planting (based on nutrient concentration in above-ground biomass and soil, litter biomass, earthworm biomass, and aggregate stability of organic particles in the soil); although statistically significant differences were found between treated and untreated plots, differences between fertilised plots with and without earthworms were not significant. Endogeic earthworms recolonised most fertilised plots, with or without earthworm introduction. Anecic earthworms did not colonize any plots. Although our findings suggest that earthworm introduction might contribute to a sustained fertiliser response in ash trees, more experiments are needed to demonstrate the precise role of earthworm introduction as part of integrated forest soil restoration.

The inverse relationship between the particle size of food resources and earthworm growth rate is widely recognised. The aim was to determine the effects of the particle size of food on interactions between combinations of adult and hatchling A. chlorotica and L. terrestris under laboratory conditions. Treatments were set up in 1 litre mesocosms, maintained in darkness at 15 ′ 1 °C. Separated cattle solids (SCS) were used as food either unmilled or milled to < 1 mm. The latter led to a 185 and 54 % increase in the mass of A. chlorotica and L. terrestris respectively, compared with unmilled SCS. Intra-specific competition in A. chlorotica was detected in adult and hatchling pairings. A positive inter-specific interaction was recorded with hatchling A. chlorotica and mature L. terrestris fed unmilled SCS with growth of the former significantly greater (P

A mixed stand of red oak (Quercus rubra) and common beech (Fagus sylvatica) on a compacted and acidified sandy loam soil was harvested and reforested with ash (Fraxinus excelsior in 1992. The ecosystem restoration trial in this newly established ash plantation included 180 trees and was set up in a block design with 4 blocks, 3 experimental groups per block and 15 trees per experimental group. Experimental groups were: (1) application of P, K, Ca and Mg fertiliser to the planting pit; (2) combined application of fertiliser and earthworms to the planting pit; and (3) a control without additional restoration measures. Fertiliser application consisted of 500 g dolomite, 100g Thomas slags and 100g kieserite; earthworm introduction consisted of 40 individuals, being 20 anecics (Lumbricus terrestris L. and Nicodrilus longus Ude) and 20 endogeics (Aporrectodea caliginosa Sav., Aporrectodea rosea Sav. and Allolobophora limicola Michaelsen). Tree growth was monitored annually. The control trees failed to grow and died after two years. Excellent growth was found for treated trees, and treatment-related growth patterns were observed: fertilised trees grew faster than fertilised trees with earthworms during the first two years, with the trend reversed from year 4 onwards. Although this trend suggested that introduced earthworms provided a more sustained response to fertiliser, this was not conclusively confirmed by an evaluation of 24 trees 10 years after planting (based on nutrient concentration in above-ground biomass and soil, litter biomass, earthworm biomass, and aggregate stability of organic particles in the soil); although statistically significant differences were found between treated and untreated plots, differences between fertilised plots with and without earthworms were not significant. Endogeic earthworms recolonised most fertilised plots, with or without earthworm introduction. Anecic earthworms did not colonize any plots. Although our findings suggest that earthworm introduction might contribute to a sustained fertiliser response in ash trees, more experiments are needed to demonstrate the precise role of earthworm introduction as part of integrated forest soil restoration.

Eukaryotic parasites residing in earthworms such as Lumbricus terrestris, have been studied for many years. However, little research has been published on the host-parasite relationship, particularly the immune response of L. terrestris and the effect of the parasite on the host. The majority of individuals belonging to the species Lumbricus terrestris are parasitized by a sporozoan of the genus Monocystis, the spores of which can be found in huge numbers in the worms' seminal vesicles. This preliminary study of the Lumbricus terrestris-Monocystis relationship attempts to determine whether a cellular reaction by the earthworm's coelomocytes (immune cells) occurs both in vivo and in vitro. Light and electron microscopic observations indicate that there is no apparent interaction between coelomocytes and parasites in the worms' seminal vesicles. However, in vitro incubations of the Monocystis spores together with coelomocytes produced an encapsulation response: a rapid attachment to and aggregation of coelomocytes around parasites, followed by a complete degranulation of the coelomocytes. The degree of degranulation was monitored by measuring acid phosphatase levels, an enzyme released during degranulation. These were subsequently compared to incubations with equal numbers of other eukaryotic parasites with thick cyst walls (Giardia and Cryptosporidium species), but which do not normally infect the worm. Acid phosphatase levels were significantly higher in Monocystis incubations compared to those of G. lamblia and Cryptosporidium, indicating a greater cellular response to the endogenous parasite. Interestingly, Giardia lamblia cysts actually inhibited degranulation compared to that of control (spontaneous degranulation) coelomocytes, a phenomenon possibly due to the nature of the cyst wall. These experiments show that whereas an immune response against the predominant spore stage of Monocystis does not occur within the seminal vesicles of the earthworm, the hosts' coelomocytes are capable of responding to these spores in vitro, and do so to a greater degree than to non-native parasites.

Earthworms affect agroecosystem processes and few studies have addressed population dynamics when earthworms are intentionally introduced. Handsorting and formalin extraction were used semi-annually from fall 1994 to fall1997 to measure populations in plots with and without added earthworms under chisel till in a corn-soybean rotation (CT) and a ridge-till system in a corn-soybean-wheat rotation (RT) in Ohio, USA. Earthworm communities were altered by adding ∼76 Lumbricus terrestris (L.) m - 2 each spring and fall into plots with no, or very few of these anecic earthworms. Increases in L. terrestris were small (∼7 m - 2 ) compared to the number added and their establishment was at the expense of the epigeic earthworm L. rubellus (Hoff.), which declined four and two-fold in CT and RT, respectively. Populations of the endogeic earthworm Octolasion tytaeum (Sav.) were unaffected by the addition of L. terrestris. Sampling 5 years after the additions indicated that L. terrestris persisted only in the RT plots. The decline in L. rubellus populations in plots with added anecic worms was no longer evident. We understand that the increased number and amounts of residues and the minimal level of disturbance found in RT probably increased the extent and quality of earthworm habitat over CT plots, which had fewer crops, less cover, and periodic disturbance. Apparently, population dynamics and competitive relationships among different earthworm functional groups were regulated by agroecosystem type, and their correspondent disturbance regimes and resource distributions.

Summary Lumbricus terrestris L. is noted for activities on the soil surface and descriptions of feeding, movement and mating have previously been recorded. The aim of this study was to investigate the effects of resource availability on these behaviours using an experimental system. The laboratory set-up consisted of an arena with a continuous area of 1 m2 with soil-filled tubes to a depth of 1 m. Eighteen mature, field-collected L. terrestris were used and fed with dried barley straw on the soil surface, either evenly or in one patch. Both patterns were applied twice over an experimental period of 56 days. An infrared video system was used to provide permanent records of a 12:12 hrs dark : light cycle. Earthworm behaviour was classified into three major groups; foraging/exploration, over-surface movements and mating, with time spent in each activity recorded for all individuals. Seventeen earthworms survived to the end of the experimental period. Surface activity peaked one hour after darkness and diminished steadily until lights up. Foraging activity increased by a factor of 1.6 in a resource-rich area whereas away from the patch it reduced by a factor of 0.8 compared with even straw distribution. Over-surface movement increased by a factor of nine after provision of a patchy straw distribution, with two thirds of movements initiated by individuals in a resource poor area. The majority of matings occurred early in the dark period. During even resource distribution, matings occurred equally in different parts of the arena whereas under patchy distribution, more matings were recorded in the resource-rich area. Presented results suggest that resource availability is an important factor affecting different aspects of surface behaviour in L terrestris.

Summary Earthworms, especially the larger anecic species such as Lumbricus terrestris, comprise the most significant component of the diet of the European badger (Meles meles) in northern Europe. The objective of the present study was to obtain baseline information on the earthworm populations in selected farms in a ‘badger removal’ area in Co. Kilkenny, and to investigate the relationships between earthworms and grassland management, and between earthworm and badger densities. Sixty eight fields in 32 farms, representing a range of grassland management intensities, were sampled between November 1999 and October 2000. Seventeen earthworm species were recorded. Mean earthworm populations (± s.e.) were 161 ± 8 individuals m–2 in November 1999 and 136 ± 9 in September – October 2000. Biomass estimates were 81 ± 5 and 69 ± 5 g m–2 respectively. Spring estimates were lower (72 ± 6 individuals m–2, 44 ± 4 g m–2), reflecting reduced earthworm activity due to dry soil conditions. ANCOVA revealed significant (P The correlations between earthworm populations and badger densities were generally weak, but when badgers located within 250 m of farm boundaries were included in the analysis, there were significant positive correlations between badger and total earthworm (r = 0.60) and L. terrestris (r = 0.40) abundance. The lack of stronger relationships probably reflects the wide availability of earthworm-rich grazed grassland suitable for badger foraging.

Summary Earthworms affect agroecosystem processes and few studies have addressed population dynamics when earthworms are intentionally introduced. Handsorting and formalin extraction were used semi-annually from fall 1994 to fall 1997 to measure populations in plots with and without added earthworms under chisel till in a corn-soybean rotation (CT) and a ridge-till system in a corn-soybean-wheat rotation (RT) in Ohio, USA. Earthworm communities were altered by adding ∼76 Lumbricus terrestris (L.) m –2 each spring and fall into plots with no, or very few of these anecic earthworms. Increases in L. terrestris were small (∼7 m –2 ) compared to the number added and their establishment was at the expense of the epigeic earthworm L. rubellus (Hoff.), which declined four and two-fold in CT and RT, respectively. Populations of the endogeic earthworm Octolasion tytaeum (Sav.) were unaffected by the addition of L. terrestris . Sampling 5 years after the additions indicated that L. terrestris persisted only in the RT plots. The decline in L. rubellus populations in plots with added anecic worms was no longer evident. We understand that the increased number and amounts of residues and the minimal level of disturbance found in RT probably increased the extent and quality of earthworm habitat over CT plots, which had fewer crops, less cover, and periodic disturbance. Apparently, population dynamics and competitive relationships among different earthworm functional groups were regulated by agroecosystem type, and their correspondent disturbance regimes and resource distributions.

Summary In situ hybridization and subsequent epifluorescence microscopy showed that passage through the anterior part of the digestive tract (pharynx, esophagus, gizzard) of Lumbricus terrestris L. reduced numbers of protozoa indigenous to soil, shifted their cell size distribution from 3—5 μm and larger towards smaller sizes (1—3 μm), and eliminated all cells with ingested bacteria. Incubation of cast resulted in a ten-fold increase of protozoan numbers, size distribution shifts towards larger cells, and the detection of large numbers of cells with ingested bacteria (up to 46% of the total number of cells). The suggestion that large cell sizes represented vegetative cells that were disrupted in the anterior part of the digestive tract, while small cells were cysts that passed the intestine unharmed and proliferate in cast was supported by feeding studies with vegetative cells and cysts of an Acanthamoeba sp. Vegetative cells were quantitatively disrupted in the anterior part of the digestive tract, while cysts passed through the digestive tract morphologically intact. Their failure to form vegetative cells in cast, however, suggested an additional physiological impact of passage through the digestive tract of L. terrestris on cysts of the Acanthamoeba sp.

Summary The taxonomic composition of microbial communities in earthworm burrow walls was studied in a laboratory experiment lasting for 165 days. Anecic earthworms Lumbricus terrestris L. were kept in microcosms containing soil and litter from a lime (Tilia cordata) and beech (Fagus sylvatica) forest. Well-developed burrow linings consisting of earthworm faeces were formed in the “Tilia” treatment, but not in the “Fagus” treatment. The numbers and dominance structure of saprophytic bacteria were determined by the plate count method. Burrow walls in the “Tilia” treatment had tenfold higher CFU numbers than the control soil. The most abundant taxa were Cellulomonasand Promicromonospora, whereas Bacillus and Streptomyces dominated in the control soil. CFU numbers did not differ between burrow walls and control soil in the “Fagus” treatment, but the dominance of Bacillus was significantly decreased in burrow walls. The structure of fungal communities was analysed by modified washing and plating method. In both treatments the dominance structure of the fungal community in burrow walls differed from that in the control soil. The fungal community in burrow walls included many litter-associated taxa (Mucor hiemalis, Trichoderma koningii, Mortierella gamsii), but its taxonomic composition was soil-specific and depended on the quantity and quality of organic matter translocated down the soil profile. Mechanisms responsible for the formation of the specific burrow wall microflora are discussed. It is concluded that L. terrestris burrow walls contribute to the maintenance of high microbial diversity in mineral soil.

The objective of this work was to obtain data on aspects of the lifecycle of Lumbricusfriendi. Field-collected specimens from NW Spain were grown to maturity and maintained under controlled laboratory conditions. Thereafter experiments were undertaken to determine mode of reproduction, reproductive output, cocoon viability and development, and hatchling growth rate. Effects of density and temperature on growth were also examined. Plastic culture vessels containing a substrate of Kettering loam were incubated in temperature-controlled chambers, with dried horse manure as food. Paired, mature animals were sampled monthly over a period of 9 months for cocoon production. Cocoons were incubated on moist filter papers in Petri dishes. Results showed that at 15 °C, individuals matured at a live mass of 3.5 g. Zero cocoons were produced by virgin animals maintained in isolation, but recently matured, paired L. friendi produced 2.16 cocoons individual−1 wk−1. Cocoons were lemon-shaped with a smooth pale yellow-coloured outer surface and had a mean mass of 28 mg. At 15 °C, cocoons required 90 days to hatch and hatchability from the first 5 months of cocoon production was 85% successful. The majority of cocoons produced a single hatchling (twins recorded < 1%). Growth of hatchlings to maturity was achieved within a period of 5 months, with tubercula pubertatis developed after 3 months. Increased temperatures in the range of 5–15 °C led to significantly increased growth rates, whereas increased earthworm density led to a significant decrease in rate of growth. These findings permit comparisons with more closely studied anecic species such as Lumbricus terrestris.

Summary Anecic earthworms Lumbricus terrestris L. were kept in laboratory microcosms containing soil and litter from a lime ( Tilia cordata ) and beech ( Fagus sylvatica ) forest. Nutrient (mineral nitrogen and phosphorus) contents, microbial activity and densities of protozoa and nematodes were determined in burrow walls and control soils after 165 days. Well-developed burrow linings consisting of earthworm faeces were formed in the “ Tilia ” treatment, but not in the “ Fagus ” treatment, presumably because beech litter was not an adequate food resource for L. terrestris . Consequently, increases in microbial biomass, basal respiration and microbial volume in burrow walls compared to surrounding soil were significant in the “ Tilia ” treatment only. However, in both treatments burrow walls were strongly enriched in mineral nitrogen and phosphorus. The density and biomass of protozoa were significantly greater in burrow walls compared to the control soil. The numbers of naked amoebae increased by similar factors of 4 and 3.5 in burrow walls of the “ Tilia ” and “ Fagus ” treatment, respectively. Flagellate density increased more than tenfold in burrow walls of the “ Tilia ” treatment but only twofold in the “ Fagus ” treatment. In addition, a comparatively large ciliate population was present in burrow walls in the “ Tilia ” treatment. The total abundance of protozoa was significantly correlated with the contents of inorganic N and P in the samples ( r = 0.68 and 0.63 respectively, P Tilia ” treatment (mostly due to bacterivorous nematodes), but was not affected in the “ Fagus ” treatment. In both treatments density of fungivorous nematodes increased, while that of plant parasites decreased in burrow walls compared to the control soil. It is concluded that the grazing pressure of protozoa and nematodes may control the dynamics of the microbial succession in earthworm burrow walls, strongly affecting nutrient cycling processes in these microhabitats.