Feeding behaviour of epi-anecic earthworm species and their impacts on soil microbial communities

Earthworms Building Up Soil Microbiota, a Review

“…Neutral effects of earthworms on soil bacterial communities have been reported by de Menezes et al (2018), who showed that the introduction of the endogeic Aporrectodea trapezoides did not influence the number of bacterial OTUs (Operational Taxonomical Units) nor the Chao1 richness estimator of the whole soil. On the other hand, positive effects on bacterial richness and diversity were observed by Hoeffner et al (2018) in the burrows created by four epi-anecic species from the Lumbricus genus, compared to the bulk soil. These authors, however, showed that fungal diversity remained unaffected by the earthworms.…”

“…The contrasting findings highlighted here may be partly explained by the different methods that were employed in the study of microbial diversity. Whilst several results were obtained by using Terminal Restriction Fragment Length Polymorphism (T-RFLP) (Egert et al, 2004;Hoeffner et al, 2018) or clone libraries of the bacterial 16S rRNA gene (Furlong et al, 2002), other studies have used next generation sequencing (NGS) to increase the resolution of diversity estimates (Gopal et al, 2017). The overall effect of earthworms on the soil microbial community also depends on soil conditions, particularly nutrient content.…”

Epi-anecic rather than strict-anecic earthworms enhance soil enzymatic activities

“…Moreover, during their activity, anecic earthworms often create middens at the entrance of their burrows (Bouché, 1977;Brown et al, 2000) which are a surface structure made up of a mix of soil, casts, mucus and buried organic matter fragments (Nielsen and Hole, 1964). Within anecic earthworms, several studies have highlighted two ecological sub-categories according to earthworm morphological traits (Briones and Álvarez-Otero, 2018), burrowing (Jégou et al, 2000(Jégou et al, , 2001Bastardie et al, 2005) and feeding behaviors (Ferrière, 1980;Eisenhauer et al, 2008;Andriuzzi et al, 2016;Larsen et al, 2016;Hoeffner et al, 2018). Thus, epi-anecic earthworms preferentially consume fresh leaf litter at the soil surface which is then buried into the soil profile whereas strictanecic earthworms consume a mix of leaf litter and humified organic matter within the soil profile (Cortez et al, 1989;Jégou et al, 1998;Stromberger et al, 2012;Larsen et al, 2016;Hoeffner et al, 2018).…”

“…The average fresh individual biomass of each earthworm species within these two ecological sub-categories can vary greatly, from 0.5 g for Lumbricus rubellus to 15.0 g for Lumbricus terrestris within epi-anecic earthworms and from 0.3 g for Aporrectodea caliginosa 5 meridionalis to 3.2 g for Aporrectodea giardi within strict-anecic earthworms (Bouché, 1972). This huge variability of biomasses between earthworm species of a same ecological sub-category suggests different metabolic needs and capacities to bury leaf litter in their burrows (Hoeffner et al, 2018). Thus, depending on both their belonging to the epi-or strict-anecic sub-categories and their individual biomass, anecic earthworm species could influence soil microorganisms.…”

A core microbiota of the plant-earthworm interaction conserved across soils

“…After one month, we applied a meticulous soil dismantling of each microcosm to separately harvest soil matrix (no macroorganisms), rhizosphere, cast and their respective bulk soils (Supporting File 1). We focussed on bacteria through 16S rRNA gene amplicon sequencing, because of their importance in the plant-earthworm interaction 16 . We also monitored the total abundance of fungi, archaea and bacteria using real-time quantitative PCR, as well as several plant traits.…”