Global introducing conference.
(Monday, July 11 – 9:10 a.m. 9:30 a.m.)

The international network on soil biodiversity (NETSOB), under the auspices of the Global Soil Partnership (GSP) of the World Food Organization (FAO) invites you all to join in.

Mr Peter de Ruiter

https://www.fao.org/global-soil-partnership/netsob/en

Session 1 - Earthworms, from soil functions to climate change
(Monday, July 11 – 9:30 a.m. 6:30 p.m)

Orals

Soil fauna diversity, greenhouse gas emissions and plant productivity: the Microbial Route or the Soil Structure Route?

Lubbers, Ingrid¹; De Deyn, Gerlinde²; Drake, Harold³; Berg, Matty^4,5; van de Putten, Wim^6,7; Leaper, Joseph²; van Groenigen, Jan Willem²

¹  Soil Geography and Landscape Group, Wageningen University, Wageningen,The Netherlands
²  Soil Biology Group, Wageningen University, Wageningen,The Netherlands
³  Department of Ecological Microbiology, University of Bayreuth, Bayreuth, Germany
⁴  Department of Ecological Science, Animal Ecology Group, Vrije Universiteit, Amsterdam, The Netherlands
⁵  Groningen Institute of Evolutionary Life Science, Community and Conservation Ecology Group, University of Groningen, Groningen, The Netherlands
⁶ Department of Terrestrial Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Wageningen, The Netherlands
⁷  Laboratory of Nematology, Wageningen University, Wageningen, The Netherlands

There is considerable interest in how soils influence global change, and through which feedback mechanisms global change may affect soil functioning. Biodiversity of the soil biome is a large contributor to the soil function-climate feedback. For example, soil fauna species can have a major impact on biogeochemical cycling of nutrients, greenhouse gas emissions and plant productivity. Earthworms therefore likely play a crucial role in the need to control soil-derived greenhouse gas emissions without reducing crop yield or soil quality.

Changes in soil fauna diversity may have substantial consequences for ecosystem processes, such as greenhouse gas emissions and plant productivity. In a proof-of principle incubation study we investigated the role of community composition and functional diversity of soil fauna with respect to these processes, and it appeared that large ecosystem engineers such as earthworms dominantly triggered faunal-induced N₂O and CO₂ emissions. The seminal finding from this experiment is that increased biodiversity of other soil fauna in the presence of earthworms decreased faunal-induced N₂O emissions and enhanced C cycling. Yet, earthworms were still the key drivers of both CO₂ and N₂O emissions.

Mechanistic explanations of this earthworm-effect are still inconclusive. On the one hand, earthworms are known to alter the microbial community structure (including N₂O producing taxa) of their gut contents, casts and burrow walls (Microbial Route). On the other hand, earthworms (‘soil ecosystem engineers’) can modify soil structural properties and thereby the transport of liquids and gases in soil (Soil Structure Route). The relative importance of these two routes with respect to earthworm-induced N₂O emissions from bulk soil was further explored within the same proof-of-principle incubation study. Finally, we investigate whether increased N₂O emissions are proportionate to the size of the ‘soil ecosystem engineer’, and whether interactions between differently sized ecosystem engineers inhibit or facilitate N₂O emissions, both in the presence and absence of plants

keywords: Soil fauna diversity; Microbial Route; Soil Structure Route; Ecosystem engineer size;N₂O emissions

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Seeking for there holy grail: definition of 6 new functional groups of earthworms according to their effect on macroporosity, bioturbation, water infiltration and litter consumption

Y. Capowiez¹, Q. Pham^2,3,4, N. Bottinelli^2,3

¹  INRAE, UMR EMMAH, Avignon, France
²  Sorbonne Université, UPEC, CNRS, IRD, INRAE, Institut d’écologie et des sciences de l’environnement IEES FEST, F-93143 Bondy, France
³  Department of Soil sciences, Soils and Fertilizers Research Institute (SFRI), Hanoi, Viet Nam
⁴  Faculty of Environmental Sciences, Vietnam National University, Hanoi, Viet Nam

The seven ecological categories of earthworms were defined by Marcel Bouché in the 70s using only morphological and anatomical characteristics. They are however often used as proxies for functional groups, i.e. to describe how earthworms influence their environment. In the present study, we studied under standardized conditions (repacked soil cores) the feeding and burrowing behavior of 40 earthworm species from Europa with 5 replicates per species. After one month, the burrows system and the bioturbation intensity were analyzed using X-ray computed tomography. The quantity of litter consumed by earthworms was also recorded. Water infiltration through each burrow system was assessed using the beerkan method. The quantitative information regarding functional effects of each species were summarized in 10 main parameters : 5 for the burrow system, 2 for bioturbation (above and below ground casts) , 1 for organic matter consumption and 2 for water infiltration (infiltration rate and breakthrough time) using PCA.  We then defined 6 new functional groups using K-means classification. These 6 groups were only partially in agreement with the ecological categories of Marcel Bouché. We first provide quantitative basis for the splitting of « anecic » earthworms into 2 functional groups (epi-anecic  and truly anecic earthworms). The main novelty is the splitting of endogeic earthworms into 2 different functional groups (hypo-endogenic and epi-endogeic earthworms). The two lasts groups were « intermediate » earthworms and « earthworms with no or low effects on the soil » which include mainly epigeic earthworms (but not only). We believe these new functional groups based on sound data will help all the soil biologist to better assess the effects of earthworm on their environment.

keywords: Ecological categories ; functional groups ; burrows ; tomography

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Two distinct ecological behaviours within anecic earthworm species in temperate climates

Kevin Hoeffner¹, Kevin R. Butt², Cécile Monard¹, Joana Frazão³, Guénola Pérès³, Daniel Cluzeau¹

¹  University of Rennes, CNRS, ECOBIO [(Ecosystèmes, biodiversité, évolution)] - UMR 6553, Rennes, France
²  University of Central Lancashire - School of Natural Sciences, Preston, PR1 2HE, United Kingdom
³  UMR SAS, INRAE, Institut Agro-AGROCAMPUS OUEST, 65 rue de Saint-Brieuc 35042 Rennes, France

Understanding the ecological behavior of earthworm species is essential to determine how earthworms interact with their environment (e.g. soil functioning, species interaction). In temperate climates, earthworm species have usually been classified into three main ecological categories according to their morpho-anatomical, physiological and ecological traits: epigeic, endogeic and anecic. However, since the definition of these ecological categories, numerous studies have been conducted on ecological traits of widespread anecic species: Lumbricus centralis (Bouché, 1972), Lumbricus terrestris(Linnaeus, 1758), Aporrectodea longa longa (Ude, 1885) and Aporrectodea giardi (Ribaucourt, 1901) highlighting two distinct feeding behaviours and resulting growth rates and burrowing behaviours. In this review we highlight that within anecic earthworms, Lumbricus anecic species (here after “LAS”) mainly consume fresh plant-derived materials on the soil surface modifying the quantity and spatial organisation of said materials. By contrast, Aporrectode aanecic species (here after “AAS”) consume mainly aged plant-derived materials already incorporated into the soil and only a small proportion of surface-available plant-derived materials. Linked to this contrasting feeding behaviour, we highlighted that AAS have a denser and more complex burrow network than LAS. This burrowing behaviour suggest that AAS burrow into the soil to search for soil organic matter incorporated in the soil whereas the LAS essentially focus on burying the surface litter into their burrow. Consequently, LAS seem to benefit from easily assimilated elements, grow faster and reach maturity in a shorter time span than AAS species. This distinction between Lumbricus and Aporrectodea earthworm species could highlight different consequences for soil trophic network and soil functioning such as carbon and nutrient cyclings, water regulation and soil structure maintenance.

keywords: Feeding guild; growth; plant-derived material; soil organic matter; burrow

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The quantification of bioturbation in soils using nanoparticles as tracers

Elma Lahive¹, Sam Harrison², Alex Robinson¹, Wiebke Mareile Heinze³, Geert Cornelis³, Denise M. Mitrano⁴, Johannes Koestel³, Emily Eagles¹, David J. Spurgeon¹, Stephen Lofts²

¹ UK Centre for Ecology and Hydrology, Maclean Building, Benson Lane, Crowmarsh Gifford, OX10 8BB, United Kingdom
²  UK Centre for Ecology and Hydrology, Lancaster Environment Centre, Lancaster, LA1 4AP, United Kingdom
³  Swedish University of Agricultural Sciences, Department of Soil and Environment, Box 7014, 75007 Uppsala, Sweden
⁴  ETH Zurich,Department of Environmental Systems Science, Universitätsstrasse 16, 8092 Zürich, Switzerland

Bioturbation is expected to influence the concentration of persistent pollutants, such as metals, in topsoils but currently this process is not considered in soil transport models. The difficulty in measuring the movement of soil particles in the soil profile, where the matrix obscures organism activity, has made bioturbation quantification challenging. Consequently, soil bioturbation rates as a result of earthworm activity are not well quantified and studies considering the contribution of different earthworm ecotypes to the bioturbation process are scarce. Particulate tracers have been utilised to characterize particle transport in sediments, and more recently in soils. Metallic nanoparticles or metal-doped nanoplastics offer a promising approach for the quantification of bioturbation processes because they can be measured by conventional analytical techniques. In this presentation the use of metal-doped (Pd) nanoplastics and metallic (Ag and In) nanoparticles to quantify bioturbation rates is explored. In a first experiment, the deep-burrowing earthworm Lumbricus terrestris was used to quantify bioturbation-driven transport of nanoplastics in soil over four weeks using palladium (Pd)-doped polystyrene nanoplastics. Sampling soil at depth revealed significant vertical transport in the soils. Higher concentrations of Pd in the burrow walls compared to the surrounding soil and Pd concentrations measured in the earthworms provided evidence that ingestion and subsequent excretion was the primary cause of redistribution. Further experiments utilising three earthworm ecotypes and two metallic (Ag and In) nanoparticle tracers added at different depths are on-going. The metal measurements in the different soil layers will be used to quantify the movement of soil in the column. Together these measurements will be used to parameterise a bioturbation model to incorporate the effects of bioturbation on the prediction of metal concentrations in topsoils.

keywords: Aporrectodea, nanoplastics, nanomaterials, transport model

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Distinct patterns of change of organic matter in bulk soil or in earthworm casts during ageing

Katell Quenea¹, Julie Leloup², Naoise Nunan², Claire Chenu³, Thomas Lerch², Valerie Pouteau³, Cedric Plessis³, Emmanuel Aubry¹

¹  Sorbonne Université, CNRS, EPHE, PSL, UMR METIS, F-75005 Paris, France
²  Sorbonne Université, CNRS, IRD, INRA, P7, UPEC, Institute of Ecology and Environmental Sciences, Paris, France
³  UMR Ecosys, INRAE AgroParisTech,  Thiverval-Grignon, France

Earthworm activities in soil generate biogenic aggregates (casts), the mass of which can reach up to 30 - 50t/ha. The dynamics of organic matter (OM) is strongly constrained (accessibility, O₂ content, etc.) within these structures and they tend to have high OM contents. As a result of their large mass and high OM contents, these aggregates can have significant effects on OM dynamics and protection over distinct time scales: (i) over the short term, earthworms increase OM mineralization through their own metabolic processes and by stimulating soil microbial activity; (ii) over longer terms, during cast ageing, a new equilibrium may be reached, leading to the protection of the incorporated OM. However few incubation studies have been conducted for more than three months. Consequently, the net influence of earthworm’s casts on the OM dynamics is still poorly understood and remains to be determined.

Our objective was to estimate whether the incorporation of fresh OM into casts leads to its protection or to an enhanced degradation during the period of cast ageing. To do so, we compared the fate of ¹³C labeled fresh OM added to bulk soil to the fate of fresh OM ingested by an epi-anecic earthworm (L. Terrestris) in mesocosms, and monitored OM mineralization during one year. The incorporation of fresh OM into casts was also determined as were the microbial communities involved in the consumption of labelled OM (via ¹³C-phospholipid fatty acid analysis).In addition, the OM stability was estimated as the proportion of mineral associated.

The results showed that fresh OM was largely incorporated into casts, with significant differences in the mineralization rates obtained for the OM incorporated into the soil, compared with that incorporated into the casts. This difference decreased over time, as the casts aged. Fungal activity was lower when OM was incorporated in casts. In conclusion, earthworms influence the fate of fresh OM in soil by delaying its mineralization but do not lead to long-term stabilization.

keywords: Organic matter fate; ¹³C labelling;  microbe succession

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Relationships between functional traits, burrowing activity and water infiltration of earthworm species found in northern Vietnam

Q.V. Pham^1,2,3, T.T.Nguyen⁴, D.H.Lam⁴, Y. Capowiez⁵, A.D.Nguyen⁶, P. Jouquet¹, T.M.Tran² and  N. Bottinelli^1,2

¹ IRD, CNRS, Sorbonne Université, Univ Paris Est Creteil, INRAe, Institute of Ecology and Environmental Sciences (iEES-Paris), F-75005 Paris, France
²  Department of Soil sciences, Soils and Fertilizers Research Institute (SFRI), Hanoi, Viet Nam
³  Faculty of Environmental Sciences, Vietnam National University, Hanoi, Viet Nam
⁴  Department of Biology, School of Education, Can Tho University, Can Tho city, Viet Nam
⁵ INRAE, UMR1114, Environment Méditerranéen et Modélisation des Agro-Hydrosystèmes, Site Agroparc, Avignon cedex 09, 84914, Paris, France
⁶ Institute of Ecology and Biological Resources, Vietnam Academy of Science and Technology, 18, Hoangquocviet, Hanoi, Vietnam

y producing burrows and dejections, earthworms influence soil properties such as soil structure and water transfers properties of soils. However, it is unknown which functional traits of earthworms determine the overall positive effects of earthworms on soil water infiltration. To achieve this goal, we systematically studied a broad suite of earthworm species regarding their functional traits and the relation of these traits to their burrowing activity and consequence on soil water infiltration. Here, we applied a trait-based approach to a set of 21 morpho-anatomical traits on 24 earthworm species including 23 Megascolecidae and 1 Glossoscolecidae sampled in northern Vietnam. For each species, one individual was incubated in a repacked soil for 4 weeks. After incubation, the 3D burrow system was measured using X-ray computed tomography and soil saturated hydraulic conductivity (Ks) was measured using the falling head method. We found large differences among species, belonging to similar or different ecological categories, in their potential effect on soil water infiltration, including neutral to positive effects. We identified the weight, length, caeca shape, thickness of the circular layerand gizzard wall as the most important traits explaining the difference in Ksat among species (Random Forest regression model with an R² = 0.9). In addition, using a co-inertia analysis, we determined that the weight, length, and caeca with manicate shape were related to the total porosity and burrow diameter, while the caeca with a simple shape were related to the density of burrows. Our findings illustrate the power of employing a trait-based approach to predict the effect of earthworms on water infiltration in comparison to the classic ecological category approach. In an applied context of restoration and agriculture, such trait information can inform management, for example to prioritize practices that favor the expression of more desirable earthworm traits to increase soil water infiltration.

keywords: Bioturbation, biostructure, soil functioning, macrofauna

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Modelling the dynamics of particulate organic matter occluded in earthworms casts during ageing under field conditions

N. Puche¹, C. Rumpel¹, G. Le Mer¹, P. Jouquet¹, A. Mazurier², L. Caner² ; P. Garnier³ ; T.M Tran⁴, N. Bottinelli^1,4

¹ RD, CNRS, Sorbonne Université, Univ Paris Est Creteil, INRAe, Institute of Ecology and Environmental Sciences (iEES-Paris), F-75005 Paris, France
²  IC2MP, UMR 7285 CNRS, Université de Poitiers, Poitiers, France
³  Université Paris-Saclay, INRAE, AgroParisTech, UMR Ecosys, 78850 Thiverval Grignon, France
⁴  Soils and Fertilizers Research Institute (SFRI), Dong Ngac, Tu Liem, Ha noi, Vietnam

Earthworms are the main soil engineers as, through their feeding and burrowing habits, they modify soil carbon dynamics and soil structure. Anecic earthworms like Amynthas Adexilis ingest surface litter and soil particles that and mixed in their guts and egest cats, deposited on the soil surface, that and usually enriched in organic matter (OM).Earthworm activity provide a pathway for the stabilization of soil organic carbon (SOC) through the formation of organo-mineral associations and the physical protection of particulate organic matter(POM) occluded in casts. However, the mechanisms and kinetics of physical protection of organic matter (OM) during casts ageing under field conditions are not taken into account in SOC dynamics models. We investigated, with the help of a biophysical SOC model and a detailed dataset from anecic earthworms (Amynthas adexilis) casts aged under field conditions for 400 days in a woodland in Northern Vietnam, the long-term OM dynamics contained in aggregates (Ctrl and casts).

To this end, we (1) developed a biogeochemical model that simulates OM dynamics modulated by the structure of the aggregates, (2) initialised the model pools, calibrated model parameters and derived the structure factor and (3) used the model to simulate the long-term dynamics of OMcontained in earthworm casts.

We first initialised the different carbon pools of the model with measured fractions of total SOC, we then calibrated the parameters of the model by using the Levenberg-Marquardt algorithm and mineralisation rates of intact aggregates measured during 80 days of a lab incubation experiment. We then optimised the structure factor and sample specific values were then correlated to the set of structural variables from the analyses of X-ray micro-tomographic images.

Our results indicated that the biochemical model performed well in simulating the CO₂ emissions from casts and Ctrl of different ages after the calibration of its parameters and the derivation of a structure factor.Our model also allowed the long-term simulation of the different fractions of OM dynamics beyond the 400 days of the field incubation that constituted the basis of our dataset.

keywords: Earthworms casts; organic carbon; physical protection; modelling; structure

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Earthworms enhance C storage in tropical soils submitted to the FBO technology

Buitrago Maria Camila^1, Garcia Amaury^1, Lavelle Patrick ^2, Velasquez Elena ¹

¹  Universidad Nacional de Colombia
²  IEES-Biodis, Paris Sorbonne Université

The FBO^℗ (Fertilisation Bio Organique) technology was applied in plantain banana crop plantations of the Colombian Valle del Cauca department.  FBO is a nucleation technique for soil restauration that creates hotspots of high biological activity by adding organic matter of respectively low quality at the bottom and high quality close to the surface. The inoculation of endogeic earthworms is expected to accelerate OM decomposition and the release of growth plant hormones.

We tested the hypothesis that organic matter (OM) inputs would enhance earthworm communities and sequestration of OM in biogenic aggregates. Soil macroaggregates >2mm were manually separated into three categories according to their physical, root or earthworm origin. The latter group in turn was separated into three categories: large (>10mm), medium (5-10mm) and small (2-5mm).

After one year, macroinvertebrate density was 36% higher with a spectacular 174% increase in endogeic Pontoscolex corethrurus and Polypheretimae longata earthworm densities, from 85.4 ± 13.7 in control to 200.6 ±11.0 ind. m^{- 2} in FBO, while epigeic Amynthas corticis increased 26.4%, from 62.8±1.5 to 79.4 ±1.3. The proportion of soil comprised in earthworm macroaggregates increased from 62.4 in control to 99.1% in FBO, with a larger increase for the small (+171%, from 4.9 to 7.2% of total) than medium (48.5% from 10.1 to 16.9%) and large (32.3%, from 49.0 to 72.4%) categories. FBO sites had a higher OM content (6.00% instead of 3.96% in control), as a result of increased accumulation in earthworm aggregates: +66.3% in the smaller, +44.9% in the intermediate and +19.2% in the largest ones. The smallest ones exhibited the largest amounts of total OM (9.84% vs. 6.16 and 4.58, respectively in medium and large sized categories). They also had the largest amounts of particulate OM (4.85% on average vs. 3.49 and 1.18% respectively in the other two categories). In addition, small macroaggregates exhibited the lowest accumulated respiration rates for 21 days, with 1.70 vs 2.07 and 2.32 in medium and large sized macroaggregates respectively.

A general quantitative balance of C stocks shows that FBO significantly enhances OM sequestration in aggregated forms, especially in the smallest 2-5 mm large category.

keywords: Soil restoration ; macroaggregation; organic matter ; Plantain banana

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Not just fishing baits! Influence of native earthworms (Oligochaeta: Sparganophilidae) on decomposition of riparian leaf litter

Roberto Carrera-Martínez¹, Melanie K. Taylor², Mac A. Callaham, Jr.², ³ and Daniel Markewitz⁴

¹  Department of Integrative Biology, University of Wisconsin – Madison, Madison, WI, USA
²  Southern Research Station, US Forest Service, Athens, GA, USA
³  Center for Marine Science, University of North Carolina at Wilmington, Wilmington, NC, USA
⁴  Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA, USA

Earthworms are known to have important impacts on leaf litter decomposition in terrestrial systems. However, their ecological roles in semiaquatic habitats have not been previously addressed. In eastern North America, this semiaquatic habitat is dominated by earthworms of the family Sparganophilidae. The basic biology and taxonomic relationships of these earthworms are not well known (although recent advances have been made). We designed an experiment to determine the effects of sparganophilid earthworms on decomposition of riparian litter.  In this experiment, we manipulated earthworms (presence or absence), and position of litter (surface or buried) in a fully factorial mesocosm study. Earthworms, sediments and leaf litter used in the study originated from Scull Shoals Experimental Forest in central Georgia, USA. Mesocosms were constructed to closely simulate stream shore conditions, consisting of saturated and unsaturated sediment. Mass loss data were collected, along with water chemistry (alkalinity, pH, PO₄, NO₃ and NH₄) and remaining litter (total C and N). Sparganophilus earthworms significantly increased the decomposition speed of surface leaf litter compared to the surface control, but not perceptibly on buried leaf litter. Water PO₄ significantly increased while alkalinity and water pH both significantly decreased with the presence of earthworms. These results hold true regardless of the positioning of the leaf litter, suggesting an important Sparganophilusrole in increasing water nutrient availability and decreasing water pH stability. The increase of litter surface decomposition by the action of earthworms suggests a potential effect of Sparganophilus on the decomposition of riparian forest litter in a relative short period of time. Significant changes in all measured water chemistry variables and enhanced litter decomposition suggests that Sparganophilusspp. may be performing as ecosystem engineersin the sediments they inhabit. Future work in freshwater ecology should take into consideration the role of these important organisms in the maintenance of nutrient cycling, interactions between terrestrial and aquatic systems and asses their biodiversity in a changing environment.

keywords: Nutrients; water chemistry; limicolous earthworms; native habitats

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Sustainable phosphorus uptake: can a combination of earthworm communities and struvite be a solution ?

Laura ME Ferron¹, Angela Sievernich¹, Selma Moerland¹, Gerwin F Koopmans², Alix MC Vidal¹, Jan Willem van Groenigen¹

¹  Soil Biology Group, Environmental Science Group, Wageningen University, the Netherlands
² Soil Chemistry and Chemical Soil Quality, Environmental Science Group, Wageningen University, the Netherlands

Conventional phosphorus (P) fertilization is unsustainable in the long term as phosphate rock mines are localized in only a few countries and are becoming increasingly depleted. More circular forms of P fertilization are necessary, and struvite (NH4MgPO4 • 6 H2O) that forms during the treatment of waste water, is among the most promising ones. However, the fertilizing properties of struvite are severely hampered by its low solubility. Earthworm activity could increase or decrease P supply from struvite to the soil through mixing activities or locally increasing soil pH respectively. We tested these potential pathways in a field-based mesocosm experiment where Lolium perennewas grown in a soil with low P status.We applied four different earthworm communities (Lumbricus rubellus, Aporrectodea longa and A.caliginosa separately and in a three-species combination) without any P fertilizer or with struvite addition. Earthworm-free controls included struvite, conventional nitrogen (N) or P fertilizer alone, full conventional N and P fertilization, and no fertilization. We performed five fertilization-harvest cycles during 12 months and measured grass P uptake and P limitation indicators (root biomass and morphology, fungal hyphae length, shoot N:P ratio). After the final harvest, we looked for earthworms in every mesocosms and subsequently identified and weighted them. Preliminary results show that most earthworm species were still represented in mesocosm were they had been introduced and although we found some earthworms in initially earthworm-free treatments, they seldomly reached the same initial densities as earthworm treatments. This bias will be addressed through modelling.Plant P uptake was highest for the full fertilization control and for any treatment fertilized with struvite (with or without earthworms). It was lower for the control without P fertilization and for earthworm treatments without struvite; and lowest for the treatment without fertilization. Our preliminary results suggest no stimulating role of earthworms in increasing or decreasing struvite-P supply to grass. The upcoming analysis of P limitation indicators will reveal if the similar plant P uptake in the presence of earthworm (versus without) is the result of identical or contrasting P uptake strategies.

keywords: Lumbricus rubellus; Aporrectodea longa; Aporrectodea caliginosa; struvite; phosphorus limitation

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Earthworm-plant-microbiota interactions

ME Hodson¹, P Brailey-Jones², W Burns³, A Harper⁴, S Hartley⁵, T Helgason⁶, HF Walker⁴

¹  Department of Environment and Geography, University of York
²  Department of Genetics, University of Georgia
³  Stockholm Environment Institute, Dept. of Environment and Geography, University of York
⁴  CNAP, Department of Biology, University of York
⁵  School of Biosciences, University of Sheffield
⁶  Department of Biology, University of York

It is well established that earthworms have a positive effect on plant growth and this is typically attributed to increased N availability. Research also shows that earthworms increase Si availability and it is known that plant Si plays a role in both drought tolerance and pest resistance in plants. Earthworms are also known to impact soil biota. We conducted a glasshouse experiment to investigate the interaction of these factors. Five different varieties of wheat were grown in greenhouse conditions and subject to combinations of presence / absence of the green morph of adult Allolobophora chlorotica (0.59 ± 0.07 g per pot; n = 40) and no drought / drought watering regimes (39 days ad hoc watering followed by either a further 17 days of watering or no watering). Earthworm aestivation occurred in drought treatments. None-the-less earthworm presence increased plant growth in both the non-drought and drought treatments, though the difference in growth was greater in the non-drought treatments. Typically trends were similar between wheat strains. When differences did occur the modern Skyfall strain showed greater biomass. Plant %N was greater in the watered treatments and, for the drought treatments was greater in the earthworm present treatments. Plant %C was greater in the presence of earthworms. In the absence of earthworms Plant %P and %Si was greater in the watered treatments and, in the watered treatments %P and %Si was greater in the absence of earthworms. Typically trends were similar between wheat strains with Skyfall occasionally showing greater concentrations. Soil pH was c. 8.1 in all treatments but was slightly decreased by the presence of earthworms and also in the watered treatments. Extractable P showed no difference across treatments. The watered treatments contained more extractable nitrate. There was more extractable Si in the drought treatment in the presence of earthworms relative to both the earthworm present watered treatments and earthworm absent drought treatments. %N did not vary with the presence or absence of earthworms but there was a significant interaction with watering regime; under drought conditions plants grown in the absence of earthworms contained less N. Bacterial and fungal beta diversity varied with both watering treatment and the presence / absence of earthworms, fungal diversity also varied between wheat strains. There were no significant interactions. Plants showed significant differences in RNA expression between both the watering and the earthworm treatments including for genes linked to N uptake.  In summary the presence of earthworms promotes plant growth under both watered and drought conditions though in this experiment the mechanism for this is unclear. Under drought conditions this does not appear to be related in a straight forward fashion to Si availability or uptake. Similarly we observed no straight forward relationship between earthworms, N (or P)and plant growth though under drought conditions the presence of earthworms promoted growth and %N in the plants despite lower extractable N in the droughted earthworm present treatments. Overall, the RNA response of plants suggests a N-related effect. Our data suggest that earthworm-promoted plant growth may be mediated by microbial effects.

keywords: plant growth; microbial diversity; A chlorotica; drought

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Earthworm invasion in meting permafrost chance or disaster – results of laboratory experiment

Jan Frouz^1,2

¹  Charles university, Benátská 2, 12800 PRAHA 2, Czech Republic
²  Biology Centre, Na Sádkách 7, 37005, České Budějovice, Czech Repubic

As global change progress, permafrost in Arctic is melting. Deeper layers of permafrost contain organic matter which gets into deeper soil by process called cryoturbation. This organic matter is protected against decomposition by permafrost freezing. Once the permafrost melts, organic matter decomposes quickly.  As the soil warms up there is potential that it may be colonized by earthworms. This was mimicked in laboratory experiment where we compare effect of litter  (Salix caprea) and earthworm (Aporectodea caliginosa) addition to mineral soil and to permafrost in terms of system respiration and stability organic matter that remained in soil. Then we measure respiration of the system for two years. New litter was added three times during experiment into all litter treatment always when litter in earthworms treatment disappear from soil surface.

After two year period both litter addition as well as earthworm increased system respiration, those effect were additive. This indicate that earthworm colonization of the sites will likely increase. However earthworm increased system respiration most strongly in initial phases of experiment latter one is much less pronounced or even disappear. At the end of experiment higher proportion of organic matter stabilized in mineral fraction has been found in earthworm treatment.

This is very artificial experiment which cannot be directly transferred in field conditions, however, experiment suggest that litter supply and earthworm invasion may speed up mineralization of organic matter released from melting permafrost. This earthworm buster of soil respiration decreased over time and more stabilized soil organic matter accumulates in earthworm treatments suggesting potential that earthworm may support carbon storage in such system in long run. However, after two years, net balance of earthworms is respiration increase.

keywords: Permafrost; carbon; respiration

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Potential respiration, (de)nitrifier and abundance in casts of Lumbricidae and Megascolecidae earthworm species are poorly linked to the three main ecological categories

Yacouba Zi¹, Quang Van Pham^1,2,3, Yvan Capowiez⁴, Cornelia Rumpel¹, Nicolas Bottinelli^1,2, Alessandro Florio⁵

¹ IRD, CNRS, Sorbonne Université, Univ Paris Est Creteil, INRAE, Institute of Ecology and Environmental Sciences (iEES-Paris), F-75005 Paris, France
²  Department of Soil sciences, Soils and Fertilizers Research Institute (SFRI), Hanoi, Viet Nam
³  Faculty of Environmental Sciences, Vietnam National University, Hanoi, Viet Nam
⁴ INRAE, UMR1114, Environment Méditerranéen et Modélisation des Agro-Hydrosystèmes, Site Agroparc, Avignon cedex 09, 84914, Paris, France
⁵ INRAE, Univ Lyon, Université Claude Bernard Lyon 1, CNRS, VetAgro Sup, UMR Ecologie Microbienne, F 69622, Villeurbanne, France

Earthworms are known to influence greenhouse gas emissions, particularly CO2 and N2O emissions through the ingestion and protection of organic matter in their casts. A laboratory experiment was performed to assess the impact of ecologically different earthworm species on soil greenhouse gas (GHG) emissions and on the abundance of microbial functional groups involved in GHG production and consumption. We measured potential nitrification, denitrification, and respiration activities as well as the abundance of the main nitrifier (by targeting bacterial and archaeal amoA genes) and denitrifier (by targeting nirK, nirS, nosZI and nosZII genes) microorganisms in casts produced in laboratory by 39 earthworm species belonging to Lumbricidae and Megascolecidae families. Earthworms were grouped into epigeic, anecic and endogeic species to test the link between the three main ecological categories and the microbial activities abundances determined by biochemical, elemental, spectroscopic and molecular analyses. We show on average higher levels of N (2-fold), C (3-fold) in Megascolecidae’s casts than control soils, regardless of the ecological categories. The amount of litter ingested and the surface casts produced by earthworms were not statically different between the three ecological categories for Megascolecidae species. Conversely, for Lumbricidae species, anecic and epigeic consumed 3 to 7 times more litter than endogeic species.

Our results indicate on average higher potential production of CO2 (by 6-fold) and N2O (by 19-fold) in casts whereas there was no significant difference for nitrification activity compared to control soils. In addition, values of potential net-to-gross N2O production ratio were always higher in control soils than casts (by 2-fold) without difference between ecological categories. We observe significant correlation between nitrification activity and AOA genes. For all the microbial activities measured, there was no significant difference between ecological categories, except for CO2 production, where largest values were measured for Megascolecidae epigeic species. We conclude that grouping earthworm into the three main ecological categories cannot explain N2O and CO2 emission potential from their casts.

keywords: greenhouse gas, epigeic, endogeic, anecic, microbial activities

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Terrestrial Zen master: transcriptomics in long term aestivation of earthworms and its termination

N. Tilikj, A. Martínez Navarro, M. Novo

Ecology and Evolution Department, Faculty of Biology, Complutense University of Madrid, Spain

Earthworms have a crucial role in the maintenance of the biotic and abiotic soil properties which is important for the biodiversity and productivity of the terrestrial ecosystems, especially in the current scenario of climate change. Aestivation is a form of dormancy witnessed in organisms living in deserts or semi-arid environments, such as the environment found in the central part of the Iberian Peninsula. This work represents a continuation of our efforts to better understand aestivation of the endogeic Mediterranean species Carpetania matritensis and also test the limits to which this earthworm can sustain itself in such unfavorable conditions. Using transcriptomic analysis we explored the changes in gene expression of different aestivation times (1 month and 1 year) as well as changes in gene expression upon termination of aestivation (2 days and 5 days after aestivation termination). Unsurprisingly the more the aestivation persisted the higher levels of gene downregulation were observed. Conversely upon aestivation termination a quick recovery of the levels of gene expression were noted, comparable to the control. Some of the downregulated genes in aestivation termination samples might be involved with the cell-division cycle. Enrichment analysis hinted at the possible importance of ion homeostasis and osmoregulation in maintaining aestivation. There was also a notable trend for downregulation of stress and immune response genes in the 1 year aestivating earthworms. This study provides the first ever transcriptomic investigation done on earthworms in such long aestivation times and in times of aestivation recovery showing the resilience and adaptability of the C.matritensis.

keywords: Adaptation; Transcriptomics ; Earthworms ; Soil dessiccation

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50 years climate change imprints on earthworm communities in mainland France

Sylvain Gérard¹, Marie Beauchesne¹, Daniel Fernández Marchán², Maeva Iannelli¹, Raphaël Della Vedova¹, Thibaud Decaëns², Claire Marsden¹, Mickaël Hedde¹

¹  Eco&Sols, INRAE, IRD, CIRAD, SupAgro Montpellier, Montpellier, France
²  CEFE, Univ Montpellier, CNRS, EPHE, IRD, Montpellier, France

Representing a quarter of world’s biodiversity, soil organisms are nowadays threatened by global changes. But little is known on how long-term climate changes impact soil fauna, including earthworms, despite their recognized importance for the functioning of soil systems. In 1972, Marcel Bouché provided a seminal work synthesizing earthworm information on about 1300 georeferenced localities distributed all over France. Resampling Bouché’s localities nowadays represents a unique opportunity to assess whether climate changes in the past 50 years have led to changes in earthworm communities in mainland France. Our main hypothesis is that (1) climate changes lead to a homogenization of earthworm communities, resulting in a higher proportion of generalist and invasive species, and a decrease in rare and endemic species, and (2) community changesare mainly found in places with stronger climate changes. We addressed this question by comparing past and current communities, focusing on taxonomic and functional α, β, and γ-diversity, on ~300 resampled localities. A preliminary analysis of data has been conducted on 40 localities in the Mediterranean region. We confirmed our hypothesis of a taxonomic homogenization, with an increase in generalist and invasive species, but we haven’t found any functional homogenization. The Mediterranean region is thought to be the most sensitive region to climate change in France, it is thus important to compare these preliminary results with those obtained elsewhere in France. They will help us to understand in a more comprehensive way the impacts of climate change on earthworm communities.

keywords: Earthworm communities ;Climate change ; France ; Diversity ; Community ecology

Posters

Bacterial communities in soil, gut and casts of Pontoscolex corethrurus under Coffea arabica and Coffea canephora

Regina M. Medina-Sauza¹, Itzel Anayansi Solís García², Manuel Blouin³, Luc Villain⁴, Roger Guevara⁵, Frédérique Reverchon², Isabelle Barois¹

¹   Red de Ecología Funcional, Instituto de Ecología A.C., Xalapa, Veracruz, Mexico.
²   Red de Estudios Moleculares Avanzados, Instituto de Ecología A.C., Pátzcuaro, Michoacán, Mexico.
³   Agroécologie, AgroSup Dijon, CNRS, INRA, Univ. Bourgogne Franche-Comté, F-21000 Dijon, France.
⁴   UMR- Interactions Plantes Microorganismes Environnement, Institut de Recherche pour le Développement (IRD) and Centre de Coopération Internationale en Recherche Agronomique pour le Développement (CIRAD), Montpellier, France.
⁵   Red de Biología Evolutiva, Instituto de Ecología A.C., Xalapa, Veracruz, Mexico.

Earthworms stimulate microbial activity in their gutand surrounding soil, through the secretion of intestinal and cutaneous mucus that induces a priming effect on the soil and gut bacterial communities, potentially modifying their structure. The objective of this work was to determinehow the presenceof tropical earthworm Pontoscolex corethrurusimpacts the structure and diversity of its associated bacterial community in the rhizosphere of ​​two coffee species, through a mesocosm experiment. The bacterial communitiesof bulk soil, rhizosphere soil, and rhizoplane of Coffea arabica and C. canephora, with and without P. corethrurus, as well as those present in the anterior and posterior sections of the earthwormgut and in excreta, were analyzed through 16S rDNA amplicon sequencing on a MiSeq Illumina platform. The bioinformatic analysis of sequences was performed in QIIME2. A greater relative abundance of Proteobacteria and Verrucomicrobia was detected in the rhizoplane than in the other compartments, whilst the relative abundance of Actinobacteria and Chloroflexi decreased in the rhizoplane. In general, the presence of earthworms increasedthe relative abundance of Bacteroidetes and Firmicutes (particularly in the rhizosphere) and decreased Actinobacteria and Patescibacteria(also in the rhizosphere). The taxonomic composition of bacterial communities in the anterior gut was markedly different than that of posterior gut and excreta both in C. arabica and C. canephora, with a dominance of Proteobacteria and Bacteroidetes. The diversity of rhizosphere bacterial community was greater in the presence of earthworms, for both coffee species. Further analyses are undergoing to determine the differences in the bacterial community structure between the different studied compartments and will help shed a light on the effect of earthworm presence for the microbial dynamic at the rhizosphere level. Up to now with these first results we conclude that earthworms modify the soil bacterial community and enrich its diversity in the rhizosphere.

keywords: Earthworm, bacterial diversity, rhizosphere, rhizoplan

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Effects of earthworms on the fate of different exogenous N in plant-soilsystem

Liping Na and Yupeng Wu

College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China

Earthworms are important ecosystem engineers that participate in soil nitrogen (N) cycling. However, the fate of newly added N in soil mediated by earthworm activity remains unclear. In order to study the fate of newly added N, we conducted a 45-day pot experiment with four different N sources included ¹⁵N-labeled rice straw,white clover straw,urea and (NH₄)₂SO₄and two earthworms (Amynthascorticis) treatments (exist or not). The amount of exogenous N uptake by, retention in soilandloss through N₂Owerethen measured. Results showed that plant¹⁵Nuptake, soil retention, and loss accounted for 8.38%-17.43%, 72.97%-85.31% and 4.31%-10.62% of the applied exogenous N, respectively. Compared with the earthworm absence treatment, earthworm presence increased N use efficiency (NUE) of ureaby 8.15% and (NH₄)₂SO₄by 10.96%, while NUE of rice straw and white clover straw decreased by12.79% and 19.27%, respectively. Earthworm presence also increased the N₂O emission and other unmeasured N losses by 36.04-161.05% and 0.76-79.39%, respectively. After incubation, earthworm presence reduced exogenous N remained in soil by 2.67-4.40%, and the retained(NH₄)₂SO₄, urea, rice straw and white clover straw were 75.08-77.14%, 76.13-79.24%, 81.55-85.31% and 72.90-76.60% respectively.

Our results indicated that earthworm activity was beneficial to promote the uptake of N fertilizers by plants, but it was not conducive to the straw Nuptake. Meanwhile, earthworm presence reduced fertilizers and straws N remained in soil, and increased the risk of environmental pollution caused by N losses.

keywords: Earthworms; 15N; Fate; Exogenous N; Plant-soilsystem

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The effects of soil composition on behavioural endpoints and energy budget of Eisenia fetida

Tamara Djerdj, Ilijana Stojkovic, Davorka K. Hackenberger, Branimir K. Hackenberger

Department of Biology, Josip Juraj Strossmayer University of Osijek, Cara Hadrijana 8/A, HR-31000 Osijek, Croatia

Earthworms play an important role in the regulation of soil physicochemical processes and ecosystem services. The burrowing activity of organisms influences physical characteristics, chemical composition, and nutrient cycling and thus affects species composition and population dynamics of other species within ecosystems. This study investigated the effects of soil composition on behavioural characteristics and energy reserves of Eisenia fetida.

The test soils were prepared using different dry weight ratios of sphagnum peat (SP), kaolin clay (KC), and quartz sand (QS). By combining the ratios of the components specified in the OECD 207/222 standards (10% : 20% : 70%), a total of 6 test soils were obtained. Earthworm behaviour was monitored during 24 hours in 2D terraria filled with test soils (water holding capacity adjusted to 50%) and quantified using a system based on deep learning. The behavioural endpoints investigated were total burrow length, burrow system complexity, and burrow reuse. To test the effects of soil composition on energy reserves, the earthworms were exposed to the test soils for 7 days. The weight of the organisms was recorded at the beginning of the experiment and after 7 days. Lipid, protein, and glycogen contents were determined after the exposure, by spectrophotometric methods.

Preliminary results suggest a correlation between soil composition and behavioural endpoints, as well as the quantities of macromolecules measured. Total length and burrow system complexity was the largest in soils containing 70% of QS and KC, while the most intensive burrow reuse was observed in soils containing 70% of SP. The mass gain was largest in soils containing 70% of SP, and a similar pattern was observed in energy reserve indicators, as well.

The results of this research can be explained by avoidance mechanisms due to mechanical irritation or reduction of energy expenditure on movement due to food availability. Both of these effects should be considered in ecological and ecotoxicological studies, and their quantification and extrapolation could help understand the processes occurring in nature.

keywords: 2D terrarium; burrow; deep learning; energy reserves

Video presentation ISEE12-S1-Djerdj_et_al.mp4

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What is the composition and stoichiometry of food consumed by Lumbricus terrestris

Anna Rożen and Dorota Twardzik

Institute of Environmental Sciences, Jagiellonian University, Kraków, Poland

The source of all elements for animals is food. A proper diet has to fulfill all needs for energy and elements. Important elements affecting the functioning of organisms are, besides the main nutrients  (C, N, P) also some other elements: Zn, Fe, Cu, Mn, Ca, Mg, K, and Na, occurring in low concentration but taking part in various vital processes in organisms. From previous experiments, we know the mismatch between earthworms' body composition and composition of available food in N, Zn, and Na.

Our study aimed to find if there are differences inelemental composition between food available and consumed by L. terrestris.

Adult L. terrestris and middens were sampled in the field. Analyzed was the composition of available food (middens) and consumed food (crop and gizzard content).

Lumbricus terrestris was selectively feeding on partly decomposed organic material. Observed were changes in the stoichiometry of ingested food during the gut passage

keywords: Earthworm; food selection; ecological stoichiometry

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Earthworms diversity and its interaction with soil properties in citrus orchards in the Gharb region, North West Morocco

Ahmed Mansour Benmrich^1,2, Mohammed Ibriz², Jamal Hallam³, Joann Whalen⁴;ZhorAbail¹

¹ Regional Center of Agricultural Research of Kenitra, National Institute of Agricultural Research, Avenue Ennasr, BP 415 Rabat Principale, 10090 Rabat, Morocco.
² Ibn Tofail University, Faculty of Sciences, Kenitra, Morocco.
³ Regional Center of Agricultural Research of Agadir, National Institute of Agricultural Research, Avenue Ennasr, BP 415 Rabat Principale, 10090 Rabat, Morocco.
⁴ Department of Natural Resource Sciences, Macdonald Campus of McGill University, Ste-Anne-de-Bellevue, Quebec, H9X3V9, Canada

Earthworms constitute an important component of soil macrofauna that play a significant role in sustaining soil fertility and plant productivity in various agroecosystems. However, these organisms are still poorly studied in Moroccan agricultural soils. In this study, we examined earthworm fauna and its interaction with soil properties in orange orchards at the Gharb region, the second largest growing area of oranges in Morocco. Eighteen Valencia orange orchards were selected for this study and three points were randomly chosen in each orchard to collect soil and earthworm samples. Soil samples were analyzed to determine their physico-chemical properties (pH, EC, CaCO₃, moisture, texture, organic C, macronutrient and micronutrient content). Earthworms were preserved in 5% formalin solution, identified to the genus or species level, counted and weighed. A total of 601 individuals were collected of which 61% were juveniles. Endogeic species were most abundant, represented by A. caliginosa (74% of total adults), A. rosea (42%), and Microscolex debius (7%). Anecic and epigeics species were totally absent. Earthworm abundance ranged from13 to 275 individual m^-2, and the biomass was between 8 and 60 g formalin-preserved weight m^-2. Significant correlations existed between earthworm abundance and total N (r = 0.43, p = 0.001), exchangeable K (r = 0.39, p = 0.006), Zn (r = 0.36, p = 0.007) and Cu (r = 0.33, p = 0.015) concentrations. Earthworm biomass was significantly correlated with soil moisture (r = 0.38, p = 0.01), clay content (r = 0.31, p = 0.036), CaCO₃ content (r = 0.39, p = 0.008), and Ca concentration (r = 0.33, p = 0.029).

keywords: Earthworm; soil; citrus; orchard; Morocco

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Relative properties of earthworm-bioturbated soil and crab-bioturbated soil collected from a wetland habitat

Ebenezer Olasunkanmi Dada, OlaideOlabimpe Fabiyi, Yusuf Olamilekan Balogun and Modupe Olatunde Akinola

¹Department of Cell Biology and Genetics, Environmental Biology Unit, Faculty of Science, University of Lagos, Akoka, Yaba, Lagos, Nigeria.

Wetlands are usually rich in bioturbating animals, whose activities modify the physicochemical and nutrient states of their habitat soil. Although, bioturbation by earthworms and crabs have been separately investigated and documented, a comparative study of their impact on soil quality is desirable. We compared the physicochemical and microbial properties of earthworm-bioturbated soil and crab-bioturbated soil from the same wetland habitat. Soils separately bioturbated by earthworms and crabs were sampled within randomly placed 1m² quadrats, and analysed for microbial, enzyme and physicochemical properties, using standard procedures. Unbioturbated (undisturbed) soil from the same proximity served as the control. Bioturbated and unbioturbated soils exhibited significant differences (p<0.05) in all the measured parameters, with unbioturbted soil showing a higher proportion of sand and silt, butlower biochemical and microbial activities. Crab-bioturabted soil had significantly higher (p<0.01) moisture and water holding capacity,relative to earthworm-bioturbated soil. However, earthworm-bioturbated soil recorded significantly higher (p<0.01) percentage nitrogen (0.45±0.02%), organic carbon (1.26±0.02%), and total organic matter (2.18±0.04%). In addition, earthworm-bioturbated soil had significantly higher total bacteria, fungi, and actinomyces counts of 129.33±18.15x10⁴CFU/g, 46.22±6.04x10⁴CFU/g, and 56.22±7.61x10⁴CFU/g, respectively. These results imply that both earthworms and crabs positively influence soil quality, but earthworm activities impact better biochemical and microbial effects. Nevertheless, efforts should be geared towards conserving the populations of wetland earthworms and crabs, as their contributions are complimentary in soil enrichment.

keywords: Soil carbon, organic carbon, soil nitrogen, enzymes, wetlands

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Do cryptic species have the same growth pattern in different soils? Do they have the same effect on the soil?

Mónica Gutiérrez-López, María Isla García de Leaniz, Sergio Jiménez-Pinadero, Irene de Sosa¹, Dolores Trigo

Biodiversity, Ecology and Evolution Department, Faculty of Biology, Complutense University of Madrid, C/José Antonio Nováis 12, 28040, Madrid, Spain.

Carpetaniaelisae and C. matritensis are two cryptic species that live in different areas in the Community of Madrid (Spain). C. elisae lives in El Tomillar at the foot of the Sierra Norte de Madrid at an altitude of 1125 m, while C. matritensis lives in El Molar at 833 m. The aim of this work is to find out if these cryptic species show the same behaviour both in their growth and in their effect on the soil. For this purpose, both species were grown in laboratory microcosms, both in their respective soils and by replacing them. The results showed that C. matritensis increases in weight under both experimental conditions, while C. elisae loses weight. On the other hand, C. matritensis, living in a more nutrient-poor soil than C. elisae, produced more faeces in both soil types, and faeces production is significantly related to weight gain, this correlation being higher for C. matritensis than for C. elisae. It was observed that the C and N content of the faeces produced by both species, when grown in the poorer soil of El Molar, was lower in the faeces than in the soil, indicating that the earthworms are forced to use all available nutrients to perform their functions, while the pH and calcium levels were always higher in the faeces than in the natural soil. In the richest soil, that of El Tomillar, no differences in nutrient content were observed between the soil and the collected faeces. It can be concluded that phylogenetically closely related species such as C. matritesnis and C. elisae have different nutritional and growth behaviour.

keywords: Carpetaniaelisae, Carpetaniamatritensis, growth, casts, nutrients

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The role of microsites in old-growth forests in maintaining earthworm diversity

Geraskina A.

Center for Forest Ecology and Productivity RAS, Moscow, Russian Federation

The efficiency of earthworms performing ecosystem functions is largely determined by not only the species composition but ecological groups composition of the of earthworms.The composition of ecological groups is determined not only by the type of forest and soil type, but also depends on the horizontal spatial heterogeneity of the forest cover.In old-growth forests, in addition to the undercrown and intercrown areas, important elements of the mosaic for soil invertebrates are deadwood of different stages of decomposition and tree-fall canopy gaps. The purpose of this research: to identify the role of microsites in maintaining the taxonomic and functional diversity of earthworms. Field researches conducted in 2013-2021 in the old-growth forests of the Northern Urals (Pechora-Ilych Nature Reserve), theMiddle Urals (Visim Nature Reserve) of the Northwest Caucasus (Teberda and Caucasus Nature Reserveses), the Far East (Sikhote-Alin, Ussuriysk and Komsomolsk Nature Reserveses) and European part of Russia (Smolensk Lakelands National Park). Microsites were selected: soil of intercrown areas, soil of undercrown areas, deadwood 2-3 stages of decomposition, canopy gaps (size 20x20 m) and moss sods on stones and rocks (in mountain forests). It has been established that the biomass of different ecological groups varies by seasons. In the spring period, greater diversity and biomass of earthworms are detected in intercrown areas and canopy gaps. In the summer period, the undercrown areas of coniferous species are especially depleted, under the crowns of deciduous trees and biomass and diversity can be high, but the highest biomass is recorded in the canopy gaps, where the highest biomass of anecic species. In moss turfs on stones, a high biomass of endogeic species. In the deadwood, the biomass of epigeic species is higher than in the soil of other types of microsites; moreover, the deadwood is temporarily populated by endogeic and even anecic species. Data collection: the State Assignment of the CEPF RAS (АААА-А18-118052400130-7), processing: RNF (21-74-20171).

keywords: Lumbricidae, deadwood, soil, reserve

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When terrestrial and marine ecologists meet: Using complementary methods (X-ray tomography and luminophores) to study earthworms bioturbation in an organic matter compartmented soil

Franck Gilbert¹, Yvan Capowiez², Audrey Vallat³, Jean-Christophe Poggiale⁴, Jean-Marc Bonzom⁵

¹ Laboratoire écologie fonctionnelle et environnement, Université de Toulouse, CNRS, Toulouse INP, Université Toulouse 3 – Paul Sabatier (UPS), Toulouse, France.
² INRAE, UMR1114, Environment Méditerranéen et Modélisation des Agro-Hydrosystèmes, Site Agroparc, 84914 Avignon cedex 09, France.
³  Institut de Radioprotection et de Sûreté Nucléaire (IRSN), PSE-ENV/SRTE, Laboratoire de recherche sur les effets des radionuclide sur les écosystèmes (LECO), Cadarache, Bât. 183, BP 3, 13115 St Paul-lez-Durance, France.
⁴  Aix-Marseille Université, Université de Toulon, CNRS, IRD, MIO UM 110, 13288, Marseille, France.

Earthworm bioturbation (both biogenic structure constructing and particle reworking) was studied using X-ray tomography combined with luminophores (colored particulate tracer), a method widely used in sediment ecology. Within laboratory repacked soils (upper half filled with a top soil containing 4% organic matter and lower half-filled with a deep soil at 2% organic matter), anecic and endogeic earthworms had contrasting reactions with only endogeic species burrowing more intensively in the upper part. More precisely, endogeic species and especially Aporrectodea caliginosa bioturbated the most soil close to the surface (3 cm depth) while the two anecic species influenced the luminophore distribution differentially with Lumbricus terrestris displacing significantly more luminophores than Aporrectodea nocturna due to intense surface activity. Results showed that luminophore displacements also provided qualitative information to complement the tomography. 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.

keywords: Soil OM composition, anecic worms, endogeic worms, quantification of bioturbation

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Ecological classification of Vietnamese earthworms: relationshipsbetween their morphology, anatomy and bioturbating behavior

Q.V. Pham^1,2,3, T.T. Nguyen⁴, D.H. Lam⁴,A.D. Nguyen⁵, Y. Capowiez⁶, P. Jouquet¹, T.M. Tran² and N. Bottinelli^1,2

¹ IRD, CNRS, Sorbonne Université, Univ Paris Est Creteil, INRAe, Institute of Ecology and Environmental Sciences (iEES-Paris), F-75005 Paris, France
²  Department of Soil sciences, Soils and Fertilizers Research Institute (SFRI), Hanoi, Viet Nam
³  Faculty of Environmental Sciences, Vietnam National University, Hanoi, Viet Nam
⁴  Department of Biology, School of Education, Can Tho University, Can Tho city, Viet Nam
⁵ Institute of Ecology and Biological Resources, Vietnam Academy of Science and Technology, 18, Hoangquocviet, Hanoi, Vietnam
⁶ INRAE, UMR1114, Environment Méditerranéen et Modélisation des Agro-Hydrosystèmes, Site Agroparc, Avignon cedex 09, 84914, Paris, France

About 250 species of earthworms have been identified in Vietnambut most of themhave yet to be classified into ecological categories, due to the lack of ecological data. To this end, we aimed to investigate the morphology, anatomy and bioturbating behavior of a large variety of earthworm species to assign them into ecological categories. We collected 47 species belonging mostly to Megascolecidae in northern and southern Vietnam. Earthworms were assigned to the seven ecological categories based on the 13 morphological and anatomical traits proposed by Bottinelli et al. (2020). In addition, we measured the bioturbating behavior of 26 species in laboratory conditions and discussed the links with the ecological categories. For each species, one individual was incubated in a repacked soil for four weeks. After incubation, we measured the consumption of litter and the production of surface casts. In addition, X-ray computed tomography was used to measure the properties of galleries such as the length, diameter, orientation, vertical distribution and percentage refilled by dejections. We found that among the 47 species, epi-endogeic species dominated (26%), followed by epi-anecic (21%), epigeic (15%) and endogeic (13%). The other categories were scantly represented with less than 10% for each. The coinertia-analysis carried out between the bioturbating behavior data and the morphology and anatomy data showed a medium relationship (RV = 0.45). This study suggests therefore the need to use other morphological and anatomical traits to identify more accurately the bioturbating behavior of Megascolecidae species.

keywords: Bioturbation; functional traits

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Do interactions among earthworms from different ecological categories change soil functioning?

José Araújo¹, Lise Dupont¹, Christian Hartmann¹, Yvan Capowiez², Thomas Lerch¹

¹  Institute of Ecology and Environmental Sciences of Paris (IEES-Paris), UMR 7618, 75005 Paris, France
²  INRAE, UMR EMMAH, Site Agroparc, 84914 Avignon cedex 09, France

While it has been shown that the diversity of plants or microorganisms plays an important role in the functioning or resilience of ecosystems, this question has not yet been clearly addressed in the literature with respect to earthworms. Yet, earthworms are the most important soil macro-organisms, whose communities are often composed of several species. The functional importance of different species is still a matter of debate since they may change their behavior according to different environmental contexts. In this experience, our hypothesis was that the impact of earthworms on soil properties depends on (i) morphological diversity of the community and (ii) soil physical environment.

To test our hypothesis 72 mesocosms (5 L) were filled with soils of 3 different textures (sandy, sandy-silty and silty), covered by a layer of green waste compost (2 cm). To test the interactions effects of earthworms 8 treatments were designed from all possible combinations of 3 different species that are abundant in a specific urban landscape: Lumbricus terrestris, Lumbricus castaneus, and Allolobophora chlorotica. The experiment lasted about 14 months in a room where air temperature, air humidity and light were controlled. Irrigation of all samples was made every month and the evolution of the amount of water retained in each sample was recorded as an indicator of the pore volume changes. Every two weeks, the soil respiration was analyzed (LI-COR chamber) as a proxy of soil biological activity. The periodic analyses of CO2 emissions and drained water suggest that the assembly of the 3 species had the strongest, although not cumulative, effects on both OM mineralization and hydric properties, excepted on the loamy soil. The ongoing analyses of soil structure by X-ray-tomography will further inform about the physical changes, and the subsequent growth of ryegrass will soon provide access to changes in primary production capacity.

keywords: Functional categories ; soil respiration ; primary production ; hydric properties

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Effects of ageing under field conditions on the stability and protection of particulate organic matter occluded in earthworms casts

N. Puche¹, C. Rumpel¹, G. Le Mer¹, P. Jouquet¹, A. Mazurier², L. Caner² ; P. Garnier³ ; T.M Tran⁴, N. Bottinelli^1,4

¹  IRD, CNRS, Sorbonne Université, Univ Paris Est Creteil, INRAe, Institute of Ecology and Environmental Sciences (iEES-Paris), F-75005 Paris, France
²  IC2MP, UMR 7285 CNRS, Université de Poitiers, Poitiers, France
³  Université Paris-Saclay, INRAE, AgroParisTech, UMR Ecosys, 78850 Thiverval Grignon, France
⁴  Soils and Fertilizers Research Institute (SFRI), Dong Ngac, Tu Liem, Ha noi, Vietnam

Through their feeding and burrowing activities, earthworms promote the inputs of organic matter (OM) to the soil and a pathway for the stabilization of soil organic carbon (SOC) through the formation of organo-mineral aggregates and the physical protection of particulate organic matter(POM)occluded in casts. After deposition on the soil surface, earthworm casts undergo destabilisation processes leading eventually to the release of protected carbon.However, the mechanisms and kinetics of OM (physical)de-protection during casts ageing are poorly understood. We investigated the effects of ageing under field conditionson the OM dynamics contained in casts produced by the anecic earthworm Amynthas adexilis in Northern Vietnam. To this end, fresh casts and control soil aggregates (Ctrl) were collected and incubated in woodland for 400 days and sampled 5 times.We investigated (1) the microscale organisation of POM and poresduring ageing, (2) correlated it to the potential carbon mineralisation.

Our results indicated that fresh casts contained significantly more POMand soil organic carbon (SOC) than Ctrl and field aged earthworm casts. Conversely, the porosity was higher in Ctrl than in casts and the porosity of casts tended to increase with their ageing. POM and pore contents amongcast samples presented strong variabilities even in the youngest aging stage. We found, on average, higher mineralisation rates for casts than for Ctrl. Carbon occluded in casts was more labile than SOC of Ctrl as indicated by their higher content of potentially mineralizable SOC (3-fold).Temporal changes of CO₂ mineralisation were related to POM connected to the outside of the cast. PhysicalPOM protection became apparent after 72 days of ageing, when the potentially mineralizable OM of casts was similar to those of Ctrl.At the end of the field experiment, casts still hadhigher POM and SOC contents (2.5 and 1.6-fold, respectively) but similar total porosity than Ctrl.

We thus conclude that earthworms provide physical protection of SOC through their impact on POM and pore spatial arrangements and in particular through increasing the contribution of POM unconnected to the outside of the cast, which may have led to prolonged SOC sequestration > 400 days.

keywords: Earthworms casts; organic carbon; physical protection; structure

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Effects of soil mechanical resistance on burrowing rates and energetics of different earthworms species

Elsa María Arrázola Vásquez¹, Mats Larsbo¹, Maria Sandin¹, Daniel Iseskog¹, Astrid Taylor², Anke Herrmann¹, Yvan Capoweiz³ and Thomas Keller^1,4

¹ Swedish University of Agricultural Sciences (SLU), Department of Soil & Environment, Box 7014, 75007 Uppsala, Sweden
² Swedish University of Agricultural Sciences (SLU), Department of Ecology, Box 7044, 75007 Uppsala, Sweden
³  INRAE UAPV – unité EMMAH, Domaine St Paul Site agroparc, 84914 Avignon cedex 9, France
⁴  Agroscope, Department of Agroecology and Environment, Reckenholzstrasse 191, 8046 Zürich, Switzerland

Burrowing by earthworms has important implications for many soil processes. Increased soil mechanical resistance, e.g. caused by soil compaction, is expected to have negative consequences on earthworm activity, but quantitative data on burrowing rates and energy requirements for burrowing as a function of soil mechanical resistance are limited. Here, we present data from laboratory experiments under controlled conditions, aiming at relating burrowing rates and energetics to soil mechanical resistance. Moreover, based on our measurements, we obtained information on whether and how the burrowing mode – by cavity expansion or ingestion – was affected by soil mechanical resistance. The experiments included monitoring burrowing activity in 2-D terraria for 72 hours, as well as measurements on energy requirements by means of respirometry and calorimetry for 48 hours. All experiments were performed at a range of different bulk densities corresponding to different levels of soil mechanical resistance, and with different earthworm species (A. longa, A. caliginosa, and A. tuberculata).

We found that burrowing rates decreased with increasing soil mechanical resistance, but that the effects were species dependent. The mode of burrowing, e.g. how much earthworms burrow via ingestion or cavity expansion, was also species dependent, but generally, burrowing by ingestion increased with increasing soil mechanical resistance. In addition, results from the 2-D terraria experiments suggest that energy requirements for creating a unit length of burrow increased with increasing soil mechanical resistance. Preliminary results from respirometry and calorimetry measurements indicate that daily earthworm energy requirements and cast production vary with soil bulk density. Data obtained from respirometry and calorimetry allow quantification of the energetics for burrowing and provide information on the links between burrowing rates, mode of burrowing and earthworm energy needs  – data analysis is currently in progress.

Our study provides quantitative data on how burrowing changes with soil mechanical resistance for different earthworm species, which is vital information for assessing impacts of soil management and climate on soil processes and functions mediated by earthworms.

keywords: bioturbation; calorimetry; epi-anecic; endogeic; respirometry

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Earthworm communities create patchy distributions in response to tree species intemperate forests

K. Haghverdi

Karaj branch, Islamic Azad University, Karaj, Iran

The forest soils can be strongly influenced by tree species. Many studies have addressed the effects of monocultures on soil earthworms, but few have examined the effects of varying ratios of species within stands. The validity of the concept of "single - tree influence circles" was tested in a forest dominated by beech and hornbeam in the north of Iran. Due to investigation the effect of forest single-trees on soil earthworm communities, twenty hectare areas of Salahedinkola forest was considered. The positions of trees with diameter at breast height (DBH) (1.3 m) more than 45cm were recorded by Geographical Position System (GPS). Three single-trees (trees with canopy cover separated from other trees and covered distinguished space) considered for soil sampling from every tree species and diameter class as three replications. All of soil samples were excavated in north aspect and at the nearest point to tree collar for more precision. Soil samples were taken at 0-15, 15-30 and 30-45cm depths. The higher values of anecic density and biomass were observed in 65-75 cm diameter class of beech (P <0.05) and 75-85 cm diameter class of hornbeam (P <0.01). Results are indicating that ecological groups of earthworms were gathered in soil different depths with higher activities in the topsoil. In general, hornbeam site had more appropriate (higher values of soil moisture, pH, total N and also lower values of C/N ratio) for earthworm's communities. These results indicate that soil landscape may be considered a mosaic of profiles reflecting the occurrence and biological characteristics of the ground cover vegetation and of individuals of the various tree species present

keywords: Hyrcanian forest, single-tree, tree diameter, soil depths, ecological groups of earthworms

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Zonal distribution of microbiome in Dendrobaena veneta

V. Khabibulina., M. Vinogradov., G., Kholostov., I., Udalov., A. Granovitch., A. Vishnyakov

Department of Invertebrate Zoology, Saint Petersburg State University, Saint-Petersburg, Russian Federation.

The classical approach to investigation of microbial communities in earthworms involves the analyses of the whole gut, whereas it is still unclear how the bacterial composition differs throughout the digestive system. In order to shed the light on this question we for the first time analyzed the microbiome structure in different gut parts of Dendrobaena veneta using amplicon sequencing of 16S RNA genes of bacteria.

The dominant groups in all parts of the D. veneta digestive system were Verrucomicrobia, Bacteroides, Actinobacteria, Patescibacteria, Planctomycetes and the most prevalent -  Proteobacteria (not less than 30% of identified sequences). Bacteria of the groups Chloroflexi, Chlamidyae, Hydrogenedentes, Firmicutes, Tenericutes and Dependentiae were significantly less presented (no more than 1-2% of identified species). Among these, only Dependentiae group was found in gut, but not in soil samples, where the earthworms were kept, also included in analyses. Interestingly, the highest relative amount of Proteobacteria species was observed in stomach – about 80% of total number. Distribution of Proteobacteria classes varied in different parts of the gut. The amount of alphaproteobacteries species in anterior part of digestive system was much higher and corresponded to the amount of these bacteria in soil samples (about 30-40%), than in posterior part (10-15 %), and vice versa the amount of delta proteobacteries species was lower in anterior part (1-8 %) and increasedto the hindgut (20-30%). A similar picture was observed for Bacteroides and Actinobacteria. During the transition from mouth to the hindgut the relative amount of the Actinobacteria species decreased from 15-20 % to 5-9 %, whereas the number of Bacteroides species increased from 1-4 % to 20-35%.

Thus the composition of bacterial community differs throughout the digestive system D. veneta, which may indicate the complex multistage processing of soil substrate.

keywords: microbiome; metabarcoding

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Does earthworm enhancement lead to changes in glomalin content in soil?

M. Kulhánek¹, B. Simon², S. Seremesic³, I. Dekemati², P. Euteneuer⁴

¹ Czech University of Life Sciences in Prague, Department of Agroenvironmental Chemistry and Plant Nutrition, Faculty of Agrobiology, Food and Natural Resources, Czech Republic
² Hungarian University of Agriculture and Life Sciences, Department of Soil Science, Institute of Environmental Sciences, Gödöllő, Hungary
³   University of Novi Sad,Department of Field and Vegetable crops, Faculty of Agriculture,Novi Sad, Serbia
⁴  University of Natural Resources and Life Science, Vienna; Department of Crop Science, Experimental Farm, Gross-Enzersdorf, Austria

Intensive soil tillage such as ploughing led to decreased earthworm (EW) abundance, arbuscular-mycorrhiza fungi (AMF) and stable soil aggregates. Earthworms and AMF are commonly known to increase soil aggregate stabilization, but can the impact of soil tillage be reversed by adding EWs? Long-term soil tillage field experiments in Austria (maize), Hungary (sunflower) and Serbia (maize) were investigated to evaluate the influence of EWson easily extractable glomalin (EEG) content as representing a group of soil AMF proteins. All three experiments had enhanced earthworm enclosures(7 m²) with additional L. terrestris (14 indiv. m^-2)underi) no-till (NT), ii) shallow cultivation (SC) and iii) ploughing (PL). Ambient EW populations adjacent to EW enclosures served as a control. Experiments weremainly realized in randomized block design with 4 replications (Austria and Hungary) and with 1 replicate in Serbia. EEG values from Austria ranged between 643-735 mg kg^-1.No-till and PL were slightly higher in EW enclosures as compared with control (not significant), but SCwere significantly higherin control. The EEG contents in Serbia (454-549 mg kg^-1) were also slightly higher in EW enclosures compared to control and PL led to lower EEG content than in NT. The samples from Hungary were taken from EW burrows, middens, and values ranged between 805–888 mg kg^-1. In Hungary, the soil tillage systems also hada high impact on EEG content and PL was lower than NT and SC. Generally, it is not possible to confirm a direct influence of EW application on EEG content in soil, but for Austria we saw a higher soil aggregate stabilization in earthworm processed soil compared to control (see ISEE 12 Poster: Euteneuer et. al: Can the smartphone application SLAKES distinguish between earthworm-influenced soil and bulk soil?)

keywords: Earthworms; Field experiments; Glomalin; Soil tillage

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Exploring the control of earthworm faeces micro- and macro-scale features on soil organic matter dynamics across species and ecological categories

Guillaume Le Mer¹, Nicolas Bottinelli¹, Marie-France Dignac¹, Pascal Jouquet¹, Yvan Capowiez², Arnaud Mazurier³, Laurent Caner3, François Baudin⁴, Cornelia Rumpel¹

¹ Institute of Ecology and Environmental Sciences- Paris (iEES-Paris) UMR CNRS, INRAE, IRD, Sorbonne University, 75005 Paris, France
²  INRAE, EMMAH, UMR 1114, Domaine Saint Paul, 84914 Avignon cedex 09, France
³ Institut de Chimie des Milieux et Matériaux de Poitiers (IC2MP), Université de Poitiers, UFR SFA, Poitiers 86073, France
⁴ Institut des Sciences de la Terre de Paris (ISTeP), Sorbonne Université, Paris 75005, France

The role of earthworms on biogeochemical carbon cycling is a major knowledge gap resulting from the difficulty of isolating and exploring the effects provided by the diversity of organisms. In this study, we investigated the effect of six earthworm species belonging to three ecological categories on soil organic carbon (SOC) mineralisation. To this end, we produced casts with the six species using subsoil material with low SOC content and miscanthus litter. Cast were subjected to laboratory ageing for 140 days. During this process, we monitored physicochemical parameters, CO2 emissions and determined the micro-scale organisation of the casts’ particulate organic matter and pores using X-ray tomography.

Our results showed contrasting properties of fresh casts from the 3 main ecological categories, in accordance with the earthworm species’ morphological or behavioral strategies, indicating that those were maintained in artificial environments. However, species-specific changes in cast properties throughout ageing increased intragroup variability among ecological categories. As a result we observed earthworm species- specific evolution of CO2 mineralisation rates during casts ageing. We found that at least half of the variability in CO2 emissions was explained by cast microstructural changes, related to the spatial arrangement between particulate organic matter, porosity, and mineral particles. We conclude that earthworm species-specific traits may play a role in organic carbon protection through their impact on microstructural cast properties.

keywords: detritivore ; faeces features ; microstructure ; C mineralisation ; physical protection

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Impact of earthworms on the fate of straw-derived ¹⁵N in a soil-plant system

Liping Na¹,Zhor Abail^2,3, Joann K. Whalen³, Bo Liang¹,Chenxiao Hu¹, Ronggui Hu¹, Yupeng Wu¹

¹  College of Resources and Environment, Huazhong Agricultural University, Wuhan, 430070, China
²  Laboratory of Soil Fertility and Plant Nutrition, National Institute of Agricultural Research, Regional Center of Kenitra, 257, Morocco
³  Department of Natural Resource Science, Macdonald Campus, McGill University, Ste Anne de Bellevue, QC H9X 3V9, Canada

Earthworms often stimulate organic nitrogen (N) mineralization, and thereby increase plant N utilization and soil N losing. However,few studies have quantified the fate of straw-derived N in arable lands with earthworm activity. In the present 45-day incubation experiment, ¹⁵N-labeled straw was incorporated into soil. Then, the amounts of straw N that was adsorbed by Lettuce, lost in the form of gas or leakage and remained in soil with and without earthworms (M. guillelmi) were measured. The presence of earthworms significantly increased the total cumulative N₂O emission but significantly decreased the straw-derived cumulative N₂O emission compared with those in the treatment without earthworms. No obvious difference was detected in straw N loss from leakage between the treatments. Lettuce biomass was increased significantly by 37% with earthworms, and a greater proportion of the N uptake by lettuce was from the soil native N pool rather than from straw N (soil-derived N in lettuce increased from 101 to 170 mg pot^-1 with earthworms). A greater proportion of straw N was recovered in large macroaggregates (> 2 mm) and in earthworm tissues in the microcosms with earthworms. Thus, the percentage of straw N that remained in the soil increased significantly from 66.1% to 70.6% with earthworm activity. In the present short period incubation experiment, the presence of earthworms stimulates the short-term mineralization of soil native N, which is available for uptake by lettuce and increase risk of losses N₂O, while temporarily stabilizing straw N in soil.

keywords: Earthworm, Straw returning, Straw-derived N, Distribution, ¹⁵N-labeling

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Earthworms restoring soil functions in reconstructed landfill soil

Martin Lampert

University of Central Lancashire

Earthworms represent the largest proportion of animal biomass in soil. Their activities shape soil structuregenerating multiple ecosystem services. Their impact can be so profoundthey are termed ‘ecosystem engineers’. Mining and landfill activities destroy soil, leading restoration practitioners to examine earthworms’ ability to rehabilitatelost functions and processes. However, damage caused by industrial activities can be so extensive, soils require re-construction before earthworms can re-colonise. Organic amendmentslike composted green waste (CGW) can be incorporated into re-constructed soils, to improve asubstrates suitability to living organisms. Several UK-based field experiments show CGW increases tree growth and earthworm abundance on former landfill reclaimed to woodland end-use. Yet, these findingare based on short-term data obtained during the first 4 years of new woodland establishment. To resolve this, severalfield experiments were revisited, with 5, 10, and 20 years having elapsed since restoration activities ceased. Tree growth, soil formation, nitrogen cycling, carbon storage, and earthworm community density and composition were evaluated, in control and amended plots. Results demonstrate that when compost accounts for15 – 25 % oftotal soil volume, increases in tree height (0.5 – 2.0 m^-1), soil organic matter (0.5 – 3.0 %), total soil carbon(6 – 15 t-ha^-1), and total nitrogen(0.5 – 2.0 t-ha^-1) can be obtained. Effect strength depends on compost quantity and is amplified by earthworms’ presence. For example, significant increases in soil total nitrogen and carbon are only recorded in the presence of earthworms and 25% compost. When earthworms are absent deposits of compost remain undecomposed below the surface, with soil formation and nitrogen cycling differing significantly.Indeed, earthworm populations rise and fall according to compost availability, whilst associations between endogeic earthworms and Italian alder emerge after 20-years. To summarise, positive feedback develops between CGW, earthworms, and certain vegetation, favouring conditions characterised as fast growing, highturnover, organic matter and nutrient rich. When soils are treated with sufficient quantities of compost, these conditions persist at 10 and 20 years demonstrating a CGW legacy effect. Useful tree, earthworm, and organic amendment combinations are suggested, which can help rehabilitate soil functions and processes in specific ecological contexts.

keywords: Earthworms; Restoration; Compost; Trees

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Earthworms in boreal forests- friends or foes?

Sylvie Quideau and Justine Lejoly

Dept of Renewable Resources, University of Alberta, Edmonton, Alberta, Canada.

The effects of earthworms on soils vary as a function of their feeding guilds, specific soil properties, and the amount and type of plant litter inputs. In agricultural soils, they are typically considered beneficial, as they improve ecosystem services such as structure, carbon sequestration, and nutrient cycling. This may not be the case in forest soils, especially in northern areas that that developed in the absence of native earthworms. Non-native European earthworms have been detected in a wide range of Canadian boreal forest soils.It is therefore critical to evaluate how North American boreal soils are responding to these ongoing earthworm invasions.

Earthworms can increase carbon losses by promoting microbial activity and the release of greenhouse gases. But they can also augment carbon storage by enhancing microbial necromass production and physically stabilizing carbon within casts. How these two opposing effects may alter the net carbon balance in Canadian boreal soils remains unclear. In this study, we compared earthworm-invaded and earthworm-free zones across Canada in key forest soil types including Luvisols, Podzols, and Brunisols (Cambisols). We observed that in most cases the forest floor (surface organic layer, or LFH) drastically decreased in overall thickness after invasion, resulting in a net carbon loss. This was accompanied by the loss of the deeper, most humified organic layer, and the formation of a Vermimull, characterized by the presence of a carbon-enriched, ≥ 2 cm-thick A horizon with a granular structure. However, while earthworm invasion increases carbon storage in the A horizon, results from a laboratory incubation show that this carbon was more easily lost by mineralization than the carbon present in earthworm-free soils. Additional results indicate that the presence of earthworms affects microbial communities and increases soil nutrient availability. Further research is needed to quantify how the influence of this earthworm invasion may be interacting with other ongoing changes such as more frequent fires in affecting the boreal biome.

keywords: Boreal forest; invasive earthworms; soil carbon; Canada

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Breakdown and build-up: the influence of Eisenia andrei on decomposition of Casuarina equisetifolia litter and composition of the soil faunal community.

Quintela-Sabarís Celestino,  Mendes Luís André, Domínguez, Jorge.

Universidade de Vigo, GEA (Grupo de Ecoloxía Animal), 36310 Vigo, Spain

She-oaks (family Casuarinaceae) have been planted in tropical areas worldwide for different uses, including remediation of soils polluted by mining, because of their tolerance to multiple soil stressors and their capacity to fix atmospheric nitrogen. However, Casuarinaceae produce recalcitrant litter that accumulates in thick layers below plant canopies. The accumulated litter has negative effects on soil restoration because it i) creates fire-prone conditions that prevent ecological succession to more mature plant communities and ii) limits the recycling of important nutrients, which remain trapped in the recalcitrant litter. Alternative methods or add-ons should therefore be sought to improve the use of Casuarinaceae in soil restoration.

Earthworms are soil ecosystem engineers that accelerate the decomposition of litter by boosting the activity of soil micro-organisms and comminution of plant debris, which in turn becomes more available for other soil detritivores (e.g., collembolans, acari). Thus, earthworms can increase soil turnover and biodiversity in recovered soils.

In the current study we investigated how the epigeic earthworm Eisenia andrei affects the rate of degradation of Casuarina equisetifolia litter and considered its role in community development. With this aim, we examined whether the presence of the earthworm increases the number and diversity of mesofauna species and the consequent degradation of the litter.

Our results point out that earthworm presence does promote the abundance of collembolan species, which can override the presence of their acari predator, accelerating the process of organic matter degradation.

This suggests that vermicomposting of Casuarina equisetifolia should be an adequate add-on to the soil recovery process in different climates

keywords: Casuarinaceae, Community, Eisenia andrei, Litterbags, Species Interaction

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WORMS AND MINERALS INFLUENCE THE BIOGEOCHEMISTRY
AND TURNOVER OF COMPOSTED ORGANIC MATTER

BARTHOD J ⁽¹⁾ , RUMPEL C ⁽¹⁾ , KOGEL-KNABER I ⁽²⁾ and DIGNAC M-F ⁽²⁾

¹  CNRS, INRA, Sorbonne U, Institute of Ecology and Environmental Sciences, Paris, France
²  Lehrstuhl für Bodenkunde, TUM, Freising-Weihenstephan, Germany

Earthworms most likely play a pivotal role in carbon stabilization through the formation of microaggregates and organomineral associations contained in their casts. However, cast formation with contrasting minerals and their effect on soil carbon sequestration and plant-soil interactions are poorly understood. To this end we carried out laboratory experiments and investigated the stability of casts formed by epigeic earthworms in the presence and absence of clay minerals and iron oxides. Additionally we assessed the effect of these decomposition products on plant growth and soil carbon transfer in a greenhouse experiment.

Our results showed that epigeic earthworms living at the soil litter interphase were able to form organo-mineral assiciations increasing the stability of organic matter. The addition of minerals during organic matter degradation increased CO₂ emissions compared to the mineral free controls either during cast production or after their addition to soil. The decomposition products produced with minerals were more favorable to plant-growth and induced stronger carbon flow to soil compared to their mineral-free counterparts. They also affected rhizosphere processes and especially microbial carbon uptake.

We conclude that the role of earthworm in favouring organic carbon stabilization and carbon input into soil must be taken into account in soil organic matter models.

keywords: Organic matter stabilization; Organo-mineral interactions; Carbon flow

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Understanding and using ecosystem services provided by earthworms (the U2 worm project)

Rumpel, C. and the U2 worm consortium

CNRS, Institute of Ecology and Environmental Sciences, Paris, France

Carbon storage and biogeochemical cycling in soil is influenced by physical, chemical and biological processes, which are most often studied separately. To overcome this limitation, we developed an interdisciplinary project gathering 9 research organisations from three countries. Under the framework of the U2 project, funded by ANR, we elucidate the impact of soil fauna, in particular earthworms, on the formation of organo-mineral interactions in biogenic aggregates. We will study these processes through a combination of field and laboratory experiments in temperate as well as tropical environments. Our research goes beyond the current state of knowledge because it is based on specific earthworm traits instead of using the traditional functional group classification. We characterize the composition and stability of earthworm casts produced by different species. In particular, the evolution of the casts’ chemical, microbiological parameters and physical organization will be studied during cast ageing. First results indicate that casts derived from different species have specific characteristics related to the species traits, which affect soil organic matter stability within the casts. This new knowledge will be used to develop new model parameters and agroecological (field) applications.

keywords: Soil carbon sequestration, earthworm traits, casts

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Organic matter composition of Amynthas kham i fresh earthworm casts as influenced by sampling time and location in Dong Cao watershed (northern Vietnam)

Xuan-Hoang DANG¹, Cornelia RUMPEL¹ ,  Pascal JOUQUET¹, Tien-Minh Tran²  and Nicolas BOTTINELLI^1,2

¹  Sorbonne U, CNRS, IRD, iEES Paris, Paris, France
²  SFRI, Dong Ngac, Tu Liem, Hanoi, Viet Nam

Earthworms play an important role in nutrient cycles of terrestrial ecosystems, through digestion and incorporation of plant litter and soil minerals into casts. Organic matter within the casts maybe protected from microbial decomposition. The timescale of protection is unknown and most probably depends on the nature of plant litter and minerals used for cast formation.

The aim of this study was to investigate the feeding behavior of Amynthas adexilis (Thai, 1984) to identify the sources of the organic and mineral constituents of earthworm casts throughout the year in two different ecosystems.

To this end, we collected earthworm casts and control aggregates at five sampling dates in woodland and meadow in northern Vietnam. We analyzed for organic C and N contents, organic matter properties using infrared spectroscopy, stable isotope composition and lignin parameters with CuO oxidation. Moreover, we used rare earth element as a fingerprint of the source of minerals used for cast formation.

Our results indicated enrichment of organic matter with low degradation in casts compared to control aggregates. Casts from woodland were clearly differentiated from those of meadow due to their lower digestibility. PCA analyses, revealed that cast composition is changing throughout the year. In woodland this may be related to changing litter availability in different seasons. In meadow this may result from soil feeding behavior under this land use.

In conclusion, A. adexilis might have different feeding strategy, reflected in contrasting cast composition in different ecosystems. The implications for organic carbon stabilization should be addressed in future studies.

keywords: Soil organic matter ; casts ; seasonal variation ; feeding behaviour ; lignin.

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High decay degree of downed trees creates hotspots of earthworm activities in temperate regions

Y. Kooch

Tarbiat Modares University, Tehran, Iran

Downed tree is an important ecological factor for changing soil properties that attracts different livings. Due to study on the decay degree effects of downed tree on soil characters and earthworms ecological groups, the Sardabrood forest located in northern Iran was considered. For this purpose, 300 ha areas considered and twenty seven downed trees of beech and hornbeam species were found. Decay degree of downed tree classified in four classes (i.e. DC1, DC2, DC3 and DC4). Whole of downed trees selected as the center of sample plots and mixed soil samples were taken from theirs besides and along at 0-10, 10-20 and 20-30cm depth. Soil pH, water content, organic C, total N and C/N ratio were measured in the laboratory. The earthworms were collected simultaneously with the soil sampling by hand sorting. The maximum of pH and water content considered in DC4 of downed tree and significant differences were found. But, soil depth had no significant differences for these characters. The higher values of soil C and N were found in DC4 of downed trees and upper layers of soil. DC1 and soil lower depths devoted the maximum of C/N ratio. Principal component analysis showed that the most assemblage of earthworms were under downed trees with high decay degree (DC4), which can be introduced as a hotspot of earthworm activities. Density and biomass of earthworms group in downed trees positions indicating endogeics are due to creating significant statistical differences between beech and hornbeam downed trees

keywords: Beech, hornbeam, epigeic, anecic, endogeic, topsoil

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Changes in remnant forest soils and earthworm communities after two decades

Ian Yesilonis^1,2, Sarah Placella³, Csaba Csuzdi⁴, Katalin Szlavecz¹

¹  Johns Hopkins University
²  USDA Forest Service
³  Root applied Sciences
⁴  Department of Zoology, Eszterházy Károly University

Long-term urban studies provide details of how soils are changing through time.  Urban soils are affected by regional and local pressures related to air pollution, and introduced species such as earthworms and vegetation which can affect change within relatively short periods of time.  Previously, we sampled forest soils of an urban-rural gradient and found that over two decades, calcium concentration and pH increased, and C:N ratios decreased.  These urban forest soils are habitat for populations of earthworms, most of which are non-native species in the families of Lumbricidae and Megascolecidae. Given the profound impact earthworms have on soil properties, we asked if the changes in soil chemistry were related to shifts in earthworm community composition and abundance, with special focus on the invasive pheretimoid earthworms.  To answer this question, we sampled earthworm assemblages in urban, suburban and rural forest patches in 2020, then compared our results with samples collected at the same locations in 2002. The results show statistically significant correlations between soil properties and earthworm abundance within a given year. For example, in 2020, canonical correspondence analysis revealed that soil variables explain 52% of the variation of the earthworm species composition.  However, changes in soil properties were independent of changes in earthworm species or abundance.  In rural forests, species and biomass changed mostly due to increases in invasive species, however, in these areas, there was little to no change in soil properties. In urban sites, species composition changed, and biomass did decrease both of which may be related to environmental factors.  The dynamics of earthworm assemblages appear to be different in urban than rural forests, consequently these assemblages uniquely affect forest ecosystems.

keywords: urban-rural gradient; Baltimore; soil function; invasive earthworms

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Small heat shock proteins as potential biomarkers for abiotic stress evaluation in E.fetida

N. Tilikj, A.B. Múñiz González, M. de la Fuente, L.J. Martínez Guitarte , M. Novo

¹Biodiversity, Ecology and Evolution Department, Faculty of Biology, Complutense University of Madrid, Spain
²Environmental Toxicology and Biology Group, Mathematical and Fluid Physics Department, Sciences Faculty, UNED; Spain

Small heat shock proteins (sHSPs) are ubiquitous proteins whose expression is quickly modified in response to environmental stressors. Unlike their counterparts the HSPs, there is very limited knowledge on their function in annelids. The aim of our study is to optimise the relative quantification of their gene expression, and subsequently analyse the expression patterns of newly identified sHSPs in the earthworm species Eisenia fetida. Short-term contact tests with different concentrations of common soil contaminants of different nature (bisphenol A, cadmium and endosulfan) as well as short-term exposure in soil to desiccation and increased temperature were employed as environmental stressors. Real time PCR was used to analyse gene expression of sHSPs. The analysis of expression patterns allows us to distinguish which of the newly identified sHSPs are constitutive proteins, or are specifically expressed as a response to stress. Furthermore, this approach has the potential to compare the expression patterns between small HSPs and HSPs and, accordingly, to get insight into putative functional relationships between them, and to obtain knowledge on how these molecules compliment the function of previously studied oxidative stress enzymes and hypoxia related proteins.

These molecules have the potential to serve as biomarkers for future evaluation of the impacts of soil contamination and Climate Change, and as such can shed light on possible adaptation soil annelids might evolve to withstand unfavourable conditions caused by anthropogenic impact and Climate Change.

keywords: Climate change; HSPs; earthworms; RT-PCR

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Earthworm diversity and soil structure and water regulation
under climate mitigation measures for agricultural soils

Faber J.H.¹, G. Peres², A.de Groot¹,P.H. Krogh³, M. Suhadolc⁴, A.Chabbi⁵

¹  Wageningen Research, Netherlands
²  Agrocampus Ouest INRAE Rennes, France
³  Århus Univ., Denmark
⁴  Univ. Ljubljana, Slovenia
⁵  INRAE Poitou Charentes, France

Climate change threatens agricultural production, and mitigation measures need to be tested for effectiveness. Subsequently, functional relationships between soil biodiversity and soil functions and the provisioning of ecosystem servicesneed evaluation. In this context, the EJP SOIL MINOTAUR project aims to assess the effectivity of mitigations measures such as reduced tillage and cropping rotation cycles including grassland on soil biodiversity and soil structure maintenance and water regulation processes.Special attention is given to quantifying the relations between soil biodiversity and microaggregate stability, and earthworms and water infiltration. Data from long-term field studies on replicated plots of different land management scenarios (grassland, arable cropping, mixed crop-grassland, reduced or conventional tillage) were analysed. Aggregate stability was measured using wet sieving method. Macropore distribution (i.e. numbers and diameter of earthworm burrows) was quantified at different horizontal layers. Infiltration rates were measured as the saturated hydraulic conductivity. Earthworms were sampled using hand sorting and chemical extraction.Data analysis demonstrated that earthworm community (species, ecological groups) was affected by land use and management practices. Aggregate stability in the top layer was significantly different among management treatments: higher under grassland vs cropping, and higher under reduced tillage vs conventional. Moreover, aggregate stability could significantly increase with earthworm biomass (anecic, endogeic). Burrow distribution and water infiltration capacity were impacted by management (permanent arable < mixed crop-grassland < permanent grassland; conventional < reduced or minimal tillage). Water infiltration capacity was related to functional diversity in earthworms, through the mediation of specific soil macropores by various species; pore systems and burrows that were connected to the soil surface contributed most efficiently to water infiltration rates. These observations indicate that the tested mitigation management practices can result in increasing earthworm functional biodiversity, and improve soil structure and water infiltration. The results provide more quantitative insights that allow for ecohydrological modelling (forecasting) and economic valuation.

keywords: Functional biodiversity; soil functions; earthworms; soil microaggregates; water infiltration

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Aestivation patterns in the Carpetania elisae cryptic complex in Madrid (Spain)

Navarro Zurro, R¹., Trigo, D.^1, Fernández Marchán, D²., JimenezPinadero, S.¹, Martínez Navarro, A.¹, Gutiérrez López, M.¹

¹ Biodiversity, Ecology and Evolution Department, Faculty of Biology, Complutense University of Madrid, C/José Antonio Nováis 12, 28040, Madrid, Spain.
²  CEFE, Univ Montpellier, CNRS, EPHE, IRD, Montpellier, France

Recent studies have shown that Carpetania elisae Álvarez (1977), previously known as Hormogaster elisae, is, actually, part of a complex of at least three cryptic species that inhabit the Iberian Peninsula. It is known that the most studied species of the complex, now called Carpetaniamatritensis, can aestivate under unfavorable environmental conditions. To investigate the possible aestivation patterns that C. elisae may present, we have studied, in laboratory experiments, its relationship with extreme environmental conditions of humidity and temperature, which could be predominant in the Iberian Peninsula in the near future, due to climate change. We found that C. elisae can aestivate, creating aestivation chambers similar to those of C. matritensis, when facing adverse environmental conditions. In this process, humidity seemed to be the main factor that influenced this behavior, as it was observed with C. matritensis. At 10% soil humidity most of the individuals aestivated, while at 20% soil humidity this phenomenon was rarely observed. Secondarily, temperature also influenced this process, with higher aestivation rates at 23ºC than at 13ºC. On the other hand, season didn’t seem to influence the aestivation of C. elisae, confirming that the type of aestivation process is, indeed, facultative diapause, also known as paradiapause, which is only caused by the shift in the environmental conditions. This wasn’t observed for C. matritensis, which appeared to aestivate more frequently in spring and summer. These results highlight the importance of ecological studies that include different cryptic species, given the fact that their behavior and resilience may vary, resulting in critical consequences for their survival when extreme environmental conditions are presented.

keywords: Earthworms; Carpetania elisae ; aestivation; cryptic species.

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Can earthworms enhance mineral weathering and thereby increase carbon sequestration?

Tullia Calogiuri^1,2, Peter Garamszegi¹,Alix Vidal¹, Jan Willem van Groenigen¹, Mathilde Hagens²

¹  Soil Biology Group, Wageningen University & Research, Wageningen, the Netherlands
² Soil Chemistry and Chemical Soil Quality Group, Wageningen University & Research, Wageningen, the Netherlands

Negative Emission Technologies (NETs) are urgently needed if we want to keep global temperature increase below 1.5 °C. Enhanced Silicate Weathering (ESW) is a NET with as yet unknown potential to mitigate climate change. There are indications that ESW rates can be amplified by biotic activity, including that of earthworms. Earlier studies have suggested various pathways through which earthworms might enhance weathering rates, including the grinding of minerals in their gizzard, the stimulation of microbial communities in their gut,as well as the production of mucus rich in organic acids and digestive enzymes. Within this research, we aim to unravel the mechanisms through which earthworms increase mineral weathering rates, and ultimately to develop a bio-reactor in which these processes are optimized. As a first step, we carried out two experiments to determine the suitability of two earthworm species and to establish the optimal conditions for earthworms and mineral weathering in a small bio-reactor. The first study tested the potential of two endogeic earthworm species, Aporrectodea caliginosa and Allolobophora chlorotica, in a system with two types of rock flours (dunite and basalt) and three organic sources (hay, straw and co-digestate). The results showed that both earthworm species can thrive and remain active in the bio-reactor in the presence of basalt mixed with either co-digestate or straw. In the second study we tested the tolerance of the same two earthworm species to two temperatures exceeding earthworms ambient levels (20°C and 25°C) and two flow rates (50 ml/day and 80 ml/day) in a system with basalt and straw. The results showed that both earthworm species can survive and remain active at the highest temperature level and the highest flow rate. Our findings demonstrate that earthworms are suitable for use in a bio-reactor and can tolerate physical conditions which are known to stimulate weathering. Future studies will elucidate to what extent earthworms can enhance weathering.

keywords: Carbon sequestration; Biogeoscience; NETs; Climate Change

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Gene expression profile of a semi-aquatic earthworm under abiotic stress.

Irene de Sosa¹, Aida Verdes², Natasha Tilikj¹, Daniel F Marchán³, Rosario Planelló⁴, Óscar Herrero⁴, Ana Almodóvar¹, Darío Díaz Cosín¹, Marta Novo¹

¹ Biodiversity, Ecology and Evolution Department, Faculty of Biology, Complutense University of Madrid, C/José Antonio Nováis 12, 28040, Madrid, Spain.
² Department of Biodiversity and EvolutionaryBiology, Museo Nacional de Ciencias Naturales, Consejo Superior de Investigaciones Científicas, C/ Jose Gutiérrez Abascal 2, 28006, Madrid, Spain.
³ CEFE, UMR 5175, CNRS–Univ Montpellier–Univ Paul–Valéry–EPHE–SupAgro Montpellier–INRA–IRD, Montpellier, France.
⁴ Biology and Environmental Toxicology Group, Faculty of Science, Universidad Nacional de Educación a Distancia (UNED), Campus UNED Las Rozas, Avda. Esparta s/n, 28232, Las Rozas de Madrid, Madrid, Spain.

In view of the current climate emergency, all animals are confronted with highly altered environmental conditions. For this reason, two experiments were conducted in which Eiseniella tetraedra was exposed to different abiotic stressors and their changes in gene expression profile were studied. In the first experiment, animals were exposed to low temperatures up to freezing point. It was found that this species was able to acclimatize to low temperatures, thanks to the upregulation of genes involved in the increase of glucose reserves. However, acclimation to freezing was less successful because the expression of genes related to the respiratory chain was reduced compared to control individuals. The second experiment consisted of reducing humidity to desiccation conditions. E. tetraedra used several mechanisms to acclimate to these adverse conditions, such as upregulation of genes related to DNA repair and reduced apoptosis.

keywords: climate change; cold; desiccation; Eiseniella tetraedra ; transcriptomics