Native Earthworm Research Articles

Microplastic contamination and earthworms: Current trends and research needs

Abstract Microplastic pollution in agricultural soils is a growing global concern that demands an urgent understanding of its effects on soil function and ecosystem services. Soil-dwelling earthworms exhibit strong subsoil bioturbation, which contributes to processes associated with many ecosystem services such as water regulation, nutrient cycling, biomass production, pollution control and remediation, among others. This functional association between earthworms and soil has made these organisms suitable candidates for assessing microplastic pollution in agricultural soils. However, based on the literature systematically reviewed here, current knowledge of microplastic toxicity in earthworms mainly derives from a recurrent methodological pattern, which implies lab-scale standardised toxicity testing. Eisenia fetida and E. andrei have been the model earthworm species (86% of screened publications), leading to the risk of biased data. Additionally, the ecological characteristics of Eisenia spp. raise uncertainties about the environmental and agronomic meaning of microplastic toxicity testing outcomes. These species are absent in agricultural lands and inhabit the soil surface, avoiding the ingestion of mineral soil. Accordingly, a more environmentally realistic assessment of microplastic pollution is needed, which involves field soil, native earthworm species as possible and aged microplastics from the environment. This review identifies specific knowledge gaps regarding the use of Eisenia species in the environmental risk assessment of microplastic pollution, and suggests moving ecotoxicity assessment towards a retrospective approach, which involves complex setups (field-simulated and ex-situ microcosms) and microplastic interactions with biomolecules and other environmental contaminants (e.g. protein corona and eco-corona) that may modulate microplastic toxicity.

Biotechnology approach of various biorefinery substrates for Thai native earthworm cultivation

Biotechnology approach of various biorefinery substrates for Thai native earthworm cultivation

Earthworm richness in no-tillage farming systems and riparian forests in Southern and Southeastern Brazil

No-tillage (NT) is a soil conservation management practice that can sustain important earthworm populations due the maintenance of soil cover and absence of soil disturbance. Sites with NT can also support native earthworm species, but few studies have identified the earthworms collected under NT. Therefore, the present study evaluated earthworm diversity in 14 sites under NT and seven with riparian forest (RF) in Atlantic Forest located in Rolândia, Cambé, Toledo (Paraná), Coxilha, Sarandi (Rio Grande do Sul) and Itaí (São Paulo). The earthworms were collected by handsorting using quantitative and qualitative methods. The 1471 individuals collected were classified into 23 species belonging to five families: Glossoscolex sp.71, sp.72, sp.73 and sp.74, Fimoscolex sp.23 sp.24 and sp.25 (Glossoscolecidae); Pontoscolex corethrurus, Urobenus brasiliensis (Rhinodrilidae); Haplodrilus sp.1 and sp.2, Ocnerodrilidae sp.1, sp.15, sp.16, sp.48, sp.49 and sp.50 (Ocnerodrilidae); Amynthas gracilis, Metaphire californica (Megascolecidae); Dichogaster affinis, D. gracilis, D. bolaui and D. saliens (Benhamiidae). Of the total, 15 were native and eight were exotic species. In general NT sites had higher species richness than the forest sites (except at Itaí), mainly due to the invasion of NT fields by exotic species, particularly Ocnerodrilidae sp.1 and Dichogaster spp. Six of the seven forests had native species, but only four NT fields had native earthworms, and these were generally found in low abundance.

Earthworms in natural grasslands and agropastoral systems in the Brazilian Pampa.

In this study, we sampled grazed natural grassland and agropastoral systems in two regions (Alegrete and Aceguá) in the highly diverse Brazilian Pampa region which is undergoing significant change in land use cover. By hand sorting the soil, a total of five species were found, belonging to the families Glossoscolecidae (Glossoscolex sp.50 and Glossoscolex sp.51), Ocnerodrilidae (Kerriona sp.6 and Eukerria sp.3), and Lumbricidae (Aporrectodea trapezoides). The former four were identified as native-new to science-and the latter as exotic. Differences were observed in both earthworm species richness and abundance between regions and land-use systems, likely due to environmental conditions and agricultural practices, respectively. Agropastoral systems had higher abundance and species richness than natural grasslands, though these differences varied by location. This suggests that conversion from natural grassland to agropastoral systems can maintain native earthworms and, possibly, enhance ecosystem services. However, an exotic species was found in high abundance at one agropastoral site. These results highlight the need for additional biodiversity studies on earthworms in the Brazilian Pampa and for research on the impacts of land use changes in this region.

An annotated checklist and distribution of earthworms from Venezuela (Megadrili: Crassiclitellata)

An earthworm checklist has produced 78 nominal taxa (species/subspecies) of earthworm reported to date in Venezuela. The list of nominal taxa was obtained through literature review and the distribution maps were plotted by ecoregion. The 78 species/subspecies are divided into 24 genera and 6 families. Native earthworm species were more widely distributed than peregrine and exotic and are more associated with the conserved areas. Exotic species had been collected mainly in the north of the country in areas with at least some disturbance history. The peregrine species P. corethrurus is also widely distributed but with a preference for disturbed areas or related to its native natural grassland condition near the Guayana's shield. This is the first accurate assessment of Venezuela's earthworm species and subspecies in the last 14 years.

Antibacterial and bacteriostatic potential of coelomic fluid and body paste of Pheretima posthuma (Vaillant, 1868) (Clitellata, Megascolecidae) against ampicillin resistant clinical bacterial isolates.

Pheretima posthuma (Vaillant, 1868), a native earthworm of Pakistan and Southeast Asia, has wide utilization in vermicomposting and bioremediation process. In this study, P. posthuma coelomic fluid (PCF) and body paste (PBP) was evaluated as antibacterial agent against ampicillin (AMP) resistant five Gram positive and four Gram negative clinical isolates. The antibacterial effect of different doses (i.e. 25-100 µg/ml) of PCF and PBP along with AMP and azithromycin (AZM) (negative and positive controls, respectively) were observed through disc diffusion and micro-dilution methods. All nine clinical isolates were noticed as AMP resistant and AZM sensitive. Antibacterial effects of PCF and PBP were dose dependent and zone of inhibitions (ZI) against all clinical isolates were between 23.4 ± 0.92 to 0 ± 00 mm. The sensitivity profile of PCF and PBP against clinical isolates was noticed as 44.44 and 55.56%, respectively. Both PCF and PBP showed bacteriostatic (BTS) action against S. aureus, S. pyogenes, K. pneumonia, N. gonorrhoeae. Moreover, the cumulative BTS potential of PCF and PBP against all isolates was 66.67 and 55.56%, respectively. The MICs of PCF and PBP were ranged from 50-200 µg/ml against selected isolates. The bacterial growth curves indicated that PCF and PBP inhibited the growth of all isolates at their specific MIC concentrations. However, PBP has better antibacterial potential compared to PCF against selected isolates. Therefore, it is concluded that both PCF and PBP of P. posthuma possess antibacterial and BTS potential against ampicillin resistant clinical isolates. This organism might be considered as a second choice of antibacterial agents and can further be utilized in pharmaceutical industries for novel drug manufacturing by prospecting bioactive potential agents.

Effects of Exotic and Native Earthworms on Soil Micro-Decomposers in a Subtropical Forest: A Field Mesocosm Experiment

Biological invasion is one of the most important factors affecting global biodiversity change, which can adversely affect ecosystem function. However, little is known about the effects of belowground biological invasions on soil ecosystems. In this study, we conducted a field-based mesocosm experiment to observe the effects of exotic and native earthworms (Pontoscolex corethrurus and Amynthas corticis, respectively) on soil nutrients and micro-decomposers (i.e., soil microorganisms and nematodes) in a subtropical forest in southern China. We found that exotic and native earthworms had different effects on nutrient availability and nematode communities in the soil. Specifically, exotic earthworms significantly decreased the content of nitrates in the soil and tended to decrease the total nematode abundance compared with native earthworms. Furthermore, nematode species richness and Shannon–Wiener index were lowest in the treatment with exotic earthworms and were the highest in the treatment with native earthworms. However, neither native nor exotic earthworms significantly affected soil microbial community composition. The results of redundancy analysis indicated that available phosphorus was positively correlated with nematode community. Our results demonstrated that exotic earthworms had adverse effects on the available nutrient content in the soil, and had a potential negative effect on the abundance of soil microfauna. These findings will be helpful in understanding the influence of exotic earthworms on soil micro-decomposers and the ecological consequences of earthworm invasion.

Are exotic earthworms threatening soil biodiversity in the Brazilian Atlantic Forest?

Invasive earthworms are threatening soil biodiversity and ecosystem functioning in formerly earthworm-free boreal and temperate forests. Although exotic earthworms are also found in tropical forests, they have received less attention from soil scientists. Here, we summarize data on earthworm populations in the native Brazilian Atlantic Forest (one of the world's 25 biodiversity hotspots) and present a case study on three forests at different regeneration stages, aiming to identify the patterns of exotic species distribution and also the possible consequences of invasive earthworms for soil ecosystem services and macrofauna communities. We found that exotic earthworms, mainly Pontoscolex corethrurus and pheretimoid species (Amynthas corticis and A. gracilis), dominated the earthworm fauna in the native Brazilian Atlantic Forest, while native earthworms were less abundant. Furthermore, we observed that exotic earthworms are probably threatening soil macroinvertebrates, especially detritivores and predators, due to the high soil bioturbation. The widespread occurrence of invasive earthworms in this biome raises concern regarding possible competition with the native soil fauna, including native earthworms, which could dramatically impact ecosystem services linked to soil, especially those related to climate regulation and water storage.

Ecological groups and isotopic niches of earthworms

Earthworms are generally categorized into three ecological groups. This categorization and its two refined versions have been widely used in studies focusing on earthworm community structure and biological invasions, as well as the effects of earthworms on vegetation, soil properties, carbon and nitrogen cycling, and ecosystem functions. We revisited this categorization system by analyzing the stable isotopes of carbon and nitrogen (13C and 15N) from 10 earthworm species commonly found in arable fields and deciduous forests in temperate North America. We showed that up to nine isotopic niches utilized by earthworms can be distinguished in the two-dimensional space delimited by δ13C and δ15N. Rather than forming distinct categories, isotopic niches of different ecological groups form a continuum, ranging from species feeding on leaf litter to those feeding on highly processed soil organic matter. Along this continuum, the three “traditional” groups are recognizable, and species of the same ecological group can exhibit considerable isotopic niche differentiation and resource partitioning. These results, together with field observations on native Lumbricidae in Europe, suggest that, despite their convenience, there are limitations to the commonly used ecological categories. We propose to incorporate stable isotopes as functional traits in studying earthworm ecology and the linkage between earthworm communities and ecosystem functions. Moreover, to fill existing knowledge gaps, the isotopic approach needs to be further expanded to native earthworm communities around the world, particularly outside Western Europe and North America, and to earthworm families and major taxonomic groups other than Lumbricidae, such as Glossoscolecidae, Acanthodrilidae, and Megascolecidae.

Agroecology niche for New Zealand's native earthworms

Exotic lumbricid earthworms have had some limited success colonising productive agricultural pastures in New Zealand, in place of native megascolecid species that did not adapt to the conversion from native vegetation cover. Native earthworms in lowland intensively-farmed landscapes are now almost entirely restricted to small fragments of native vegetation on marginal land where they coexist with adventive lumbricids. In recent years, regular pasture replacement using cultivation has been largely replaced by herbicide spray-out followed by direct drilling; much less soil disturbance potentially creates a new opportunity for native earthworms to colonise pastures. Reclaiming native earthworm habitat is critical not only to protecting diversity, but also to sustaining New Zealand's unique soil ecosystem services strongly associated to role of native species; however, there have been no studies related to this. Using a mesocosm experiment, we investigated how native and exotic earthworms modify physicochemical properties of a sheep-grazed pasture soil. The pasture soil was found to be equally suitable for the growth and survival of native and exotic species. Most burrowing earthworms increased the more soluble forms of macronutrients (N, P, S, K and Mg), but differences between native and exotic species were found to be larger than between functional groups. Two species of native earthworms, Octochaetus multiporus and Maoridrilus transalpinus, modified some soil properties in similar way to exotic species, but had significantly different impacts on pH, mineralisation of nutrients, and plant availability of trace elements. Compared to control, plant available N (PAN) and S concentrations were higher by more than 100% and 40%, respectively, in soils with presence of burrowing activity of the two native earthworms. Future co-existence of communities of native and exotic earthworms in agricultural pastures appears realistic, and this would benefit conservation of native species as well as dairy production. Further research may also reveal additional and unique benefits to soil quality that could be attributable to this formerly unavailable niche for native earthworms.

Growth and Pb Uptake of Brassica campestris Enhanced by Two Ecological Earthworm Species in Relation to Soil Physicochemical Properties

A comprehensive understanding of the influence of earthworms on the growth and Pb accumulation of leafy vegetables is significant for soil management and human health. This study was aimed to evaluate the different influences of two ecological earthworm species on the growth and Pb accumulation of Brassica campestris in a Pb-contaminated soil and their relationship with soil physico-chemical properties. In a 30-day microcosm experiment, the anecic and native earthworm species Amynthas aspergillum and the epigeic species Eisenia fetida were inoculated in soil artificially contaminated with Pb at different levels (i.e., 0, 100, 500, and 1,000 mg kg−1), and B. campestris was grown. With a survival rate of 81%–100%, A. aspergillum was more tolerant to Pb contamination than E. fetida with 46%–84%. At the same time, earthworm inoculation significantly increased soil Pb bioavailability (p < 0.05). At the 500 and 1,000 mg kg−1 Pb levels, the treatments with earthworm inoculation showed higher plant biomass, leaf area, and chlorophyll concentration than the treatments without earthworm. The principal component analysis (PCA) showed that earthworm inoculation exerted a stronger effect on soil properties than Pb contamination, but the latter had a stronger effect on plant growth and Pb accumulation. Compared with A. aspergillum, E. fetida had a greater effect on soil cation exchange capacity, available Pb, and plant growth and Pb accumulation. In contrast, A. aspergillum had a greater effect on soil C and N contents than E. fetida. The co-inertia analysis revealed that plant Pb accumulation was positively correlated with soil available Pb and CEC. The leaf chlorophyll concentration was closely related to soil Eh, pH, and Dissolved organic carbon. The findings of this study showed that in the Pb-contaminated soils, earthworm inoculation exerted a strong effect on soil physicochemical properties and the growth and Pb accumulation of the leafy vegetable B. campestris. Both the epigeic earthworm species E. fetida and the anecic species A. aspergillum were associated with higher Pb accumulation or concentration in B. campestris, which may bring a possible risk to food security.

Soil Contamination and Bioaccumulation of Heavy Metals by a Tropical Earthworm Species (Alma nilotica) at Informal E‐Waste Recycling Sites in Douala, Cameroon

Soil contamination at electronic waste (e-waste) recycling sites is pervasive, though many locations have yet to be studied. While such contamination can present risks to soil organisms, little is known on the risks to native species. The objective of the present study was to assess soil contamination by heavy metals at e-waste recycling sites, and the potential of Alma nilotica, a native earthworm species, to bioaccumulate these metals. Soil samples collected from eight informal e-waste recycling sites and two non-e-waste sites in Douala, Cameroon, were analyzed for metal content. Metal concentrations in earthworm juveniles exposed to the soils for 21 days followed by a 14-day post-exposure period were measured weekly. Mean soil metal concentrations at e-waste sites ranked as Cu > Pb > Zn > Hg > Ni > As > Cd > Co > Cr. Based on contamination factors, soil contamination ranged from "moderate" (Cr), through "considerable" (Co and Cd), to "very high" for the rest of the metals. Based on the modified degree of contamination and risk index, all e-waste sites had "ultra-high" contamination with Ni, Pb, and Zn posing very high ecological risks and Bonaberi being the most contaminated site. There was a positive correlation between soil metal concentrations and metal accumulation (retention) by eathworms, but Hg and Co had the highest bioaccumulation factors (BAFs) despite having low soil concentrations. These results document that e-waste sites in Douala are contaminated with metals and that native earthworm species can bioaccumulate the studied metals at levels that could account for the toxic effects earlier recorded. With e-waste recycling growing worldwide, there is a need for more data, especially from understudied locations. Environ Toxicol Chem 2022;41:356-368. © 2021 SETAC.

Value addition to livestock excreta and fish waste through vermicomposting

The feasibility of value addition to different livestock excreta and fish waste through native earthworms was assessed in this study. Vermicomposting of livestock excreta with fish waste showed differences. The composting of goat pellet was completed in 45 days and it was 35 days for that of cow, horse and buffalo dung. Productivity ranged between 89.56% and 92.96%. Assessment of physico-chemical parameters indicated maximum levels of all the parameters estimated in the compost produced from cow–fish combination. The maximum C:N ratio recorded was 10:8 in the compost produced by goat- fish combination and that of cow – fish combination was estimated to be a minimum of 9:9.

A new genus and species of earthworm (Oligochaeta: Megascolecidae) from semi-arid Australia

A new genus and species of terrestrial oligochaete, Aridulodrilus molesworthae (Megascolecidae) is described from a new species found in a semi-arid habitat in New South Wales, Australia. The location of this species provides additional evidence that localized landscape and pedologic factors have allowed isolated populations of native earthworms to persist in areas where low rainfall averages were previously thought to preclude their occurrence. The genus has a combination of morphological features that distinguish it from all other Australian genera. While it shares some features with genera in Western Australia, the wide geographic gap (some 2300 km) appears to preclude any close phylogenetic affinity with these taxa.

The Nectar of Life

In response to an agrarian crisis, small-scale farmers in South India are experimenting with the application of agricultural ferments to their degraded soils. This article focuses on the Nectar of Life, a fermented preparation made by practitioners of Zero Budget Natural Farming out of the urine and dung of native cows. Based on ethnography in Wayanad, Kerala, and textual analysis of statements by Subhash Palekar, the inventor of the ferment, I unpack its recipe ingredient by ingredient and show that fermenting the Nectar of Life enacts a microbial ontology of agriculture. Through fermentation, natural farmers rethink soil care as a fundamentally relational activity that requires humans, cows, plants, and microorganisms to work together for mutual benefit. However, fermentation and natural farming are also implicated in what I call bionativism, a nativism focused on biological belonging. The native cow as the cornerstone species of probiotic fermentation makes microbial thinking compatible with nativist politics and tropes of the Hindu Right. I analyze the ambivalences of combining probiotic perspectives on more-than-human health with a rejection of alien species. I show how fermentation practices produce not only living soils but also nativist objects such as native cows, native earthworms, and native soils as well as their foreign enemies.

Effects of Electronic and Electrical Waste-Contaminated Soils on Growth and Reproduction of Earthworm (Alma nilotica).

Informal recycling of electronic waste (e-waste) contaminates local environments with metals and other organic compounds. The adverse effects on native earthworm populations are poorly understood. The objective of the present study was to determine metal concentrations in soils from e-waste activity sites in Douala (Cameroon) and assess the effects of these soils on the growth and reproduction of the local earthworm, Alma nilotica. Concentrations of nine metals (arsenic [As], cadmium [Cd], cobalt [Co], chromium [Cr], copper [Cu], mercury [Hg], nickel [Ni], lead [Pb], and zinc [Zn]) were measured in soil samples collected from eight e-waste activity and two non-e-waste sites. Earthworms were then exposed to these soils in the laboratory following test guidelines of the Organisation for Economic Co-operation and Development. Metal concentrations in the e-waste-contaminated soils were significantly higher than in the non-e-waste soils. The e-waste soils were found to have a different soil metal profile (Cu > Pb > Zn > Cr > Ni > Co > As > Cd > Hg) from that of the non-e-waste soils (Zn > Cr > Cu > Pb > Ni > As > Cd > Co > Hg). Earthworm growth and reproduction were significantly inhibited in organisms exposed to soils from e-waste sites. Reproduction was particularly affected, with a mean of 8 ± 5.6 offspring/10 worms in the e-waste-exposed worm groups compared with 90.5 ± 0.7 in non-e-waste soil worms. Notably, earthworm growth recovered during depuration in clean soil, indicating the possibility of remediation activities. The results demonstrate that soils at e-waste sites can affect the health of resident worm populations, which may be more sensitive than temperate species. They also highlight the potential of a bioassay-based approach in monitoring risks at e-waste sites. Environ Toxicol Chem 2022;41:287-297. © 2021 SETAC.

Potentiality of Vermicomposting in the South Pacific Island Countries: A Review

Incorporation of vermin culture in the composting system produces “vermicompost”, an enriched biofertilizer known to improve the physical, chemical, and biological properties of soil. It is applied in granular form and/or in liquid solution (vermiwash), and in both open fields and greenhouses. Vermicompost has been shown to contain plant growth hormones, which stimulate seed germination and improve crop yield, the ‘marketability’ of products, plant physiology, and their ability to fight against disease. In recent years, South Pacific island countries (SPICs) have placed an increasing emphasis on the importance of organic agricultural practices as a means of achieving more sustainable and environmentally friendly farming practices. However, vermiculture is not practiced in South Pacific island countries (SPICs) largely due to the lack of awareness of this type of application. We consider the inclusion of vermiculture in this region as a potential means of achieving sustainable organic agricultural practices. This study represents a systematic review in which we collect relevant information on vermicomposting and analyze the applicability of this practice in the SPICs based on these nations’ physical, socioeconomic, and climatic conditions. The tropical climate of the SPICs means that they meet the combined requirements of a large available biomass for composting and the availability of earthworms. Perionyx excavatus and Pontoscolex corethrurus have been identified as potential native earthworm species for vermicomposting under the conditions of the SPICs. Eisenia fetida, a well-known earthworm species, is also effectively adapted to this region and reported to be an efficient species for commercial vermicomposting. However, as a new input into the local production system, there may be unforeseen barriers in the initial stages, as with other advanced technologies, and the introduction of vermiculture as a practice requires a steady effort and adaptive research to achieve success. Further experimental research is required to analyze the productivity and profitability of using the identified native earthworm species for vermiculture using locally available biomass in the SPICs.

Neuroendocrine control of cocoon production in native earthworm Perionyx ceylanensis subjected to seasonal variation

Aim: The aim of the present study was to observe the role of cerebral ganglionic neurosecretory cells (NSCs) during cocoon production in native earthworm species Perionyx ceylanensis subjected to amputation and seasonal variations. Methodology: Histological studies (using Aldehyde Fuchsin and Chrome Alum Haematoxylin Phloxin stain) were carried out on brain NSCs in the two groups of earthworms (Group I and Group II) maintained in earthen culture pots (2L) with cowdung as food. Group I comprised of brain amputed earthworms was subjected to observe the role of brain NSCs in production of cocoon and Group II earthworms subjected to seasonal changes in the cerebral NSCs during cocoon production. Five replications were kept for Group I (1 individual per pot) and Group II (1 pair per pot). Results: Group I debrained earthworms started to lay cocoons from the 31st day following regeneration of cerebral ganglionic type A NSCs. In group II worms the highest neurosecretory activity was registered in the cerebral type A cells, especially during monsoon coinciding with the hike of cocoon generation. Interpretation: Appearance of type A NSCs in regenerated brain and peak of type A neurosecretory cell activity during peak reproductive period of earthworm species (as indicated by peak of cocoon production) indicates the possible role of cerebral type A NSCs in cocoon laying.

A contribution to the earthworm diversity (Clitellata, Moniligastridae) of Kerala, a component of the Western Ghats biodiversity hotspot, India, using integrated taxonomy

Earthworms (Clitellata, Moniligastridae) of Chaliyar River Malappuram, Eravikulam National Park, Neyyar Wildlife Sanctuary, Parambikulam Tiger Reserve, Peppara Wildlife Sanctuary, Periyar National Park, Shendurney Wildlife Sanctuary and Wayanad Forest, Kerala, a component of the hotspot of Western Ghats, India, were studied by the standard method of taxonomy, and their DNA barcode signatures using the mitochondrial gene cytochrome c oxidase I (COI) were generated for the first time. This study represents eleven species of earthworms of the family Moniligastridae: Drawida brunnea Stephenson, Drawida circumpapillata Aiyer, Drawida ghatensis Michaelsen, Drawida impertusa Stephenson, Drawida nilamburensis (Bourne), Drawida robusta (Bourne), Drawida scandens Rao, Drawida travancorense Michaelsen, Moniligaster aiyeri Gates, Moniligaster deshayesi Perrier, and Moniligaster gravelyi (Stephenson). In the phylogenetic analysis all the species were recovered in both neighbour–joining (NJ) and maximum likelihood (ML) trees with high clade support. The average K2P distance within and between species was 1.2 % and 22 %, whereas the clear barcode gap of 2–5 % was suggested by barcode gap analysis (BGA) of studied species, reflecting the accuracy of characterization. The study presents the first step in the molecular characterization of the native earthworm family Moniligastridae of India. Data published through GBIF (Doi: 10.15470/l2nlhz)

Invasive plants exert disproportionately negative allelopathic effects on the growth and physiology of the earthworm Eisenia fetida

Exotic invasive plants possess the capacity to disrupt and extirpate populations of native species. Native plants' increased sensitivity to invaders' allelochemicals is a mechanism by which this can occur. However, it is not clear whether and how the allelopathic effects of invasive plants affect members of the soil faunal community — particularly the important functional guild of earthworms. We used the model earthworm Eisenia fetida to investigate the responses to extracts from the widely invasive Asterids (Ageratina adenophora, Bidens pilosa, Erigeron annuus) and closely-related native species in a greenhouse experiment. We observed declines in body mass and respiration, and increases in oxidative and DNA damage biomarkers in the native earthworm E. fetida when grown under root and leaf extracts from these invasive plants. These effects were concentration-dependent, and worm growth and physiology was most negatively affected under the highest concentrations of leaf extracts. Most importantly, extracts from invasive plants caused significantly more negative effects on E. fetida than did extracts from native plant species, indicating allelopathy from invasive plants may inhibit earthworm physiological functioning. These results expand the domain of the novel weapons hypothesis to the earthworm guild and demonstrate the utility of E. fetida as a bioindicator for plant allelochemicals.