Earthworm Species Research Articles

Ecologically different earthworm species are the driving force of microbial hotspots influencing Pb uptake by the leafy vegetable Brassica campestris.

Food chain contamination by soil lead (Pb), beginning with Pb uptake by leafy vegetables, is a threat to food safety and poses a potential risk to human health. This study highlights the importance of two ecologically different earthworm species (the anecic species Amynthas aspergillum and the epigeic species Eisenia fetida) as the driving force of microbial hotspots to enhance Pb accumulation in the leafy vegetable Brassica campestris at different Pb contamination levels (0, 100, 500, and 1,000 mg·kg-1). The fingerprints of phospholipid fatty acids (PLFAs) were employed to reveal the microbial mechanism of Pb accumulation involving earthworm-plant interaction, as PLFAs provide a general profile of soil microbial biomass and community structure. The results showed that Gram-positive (G+) bacteria dominated the microbial community. At 0 mg·kg-1 Pb, the presence of earthworms significantly reduced the total PLFAs. The maximum total of PLFAs was found at 100 mg·kg-1 Pb with E. fetida inoculation. A significant shift in the bacterial community was observed in the treatments with E. fetida inoculation at 500 and 1,000 mg·kg-1 Pb, where the G+/G- bacteria ratio was significantly decreased compared to no earthworm inoculation. Principal component analysis (PCA) showed that E. fetida had a greater effect on soil microbial hotspots than A. aspergillum, thus having a greater effect on the Pb uptake by B. campestris. Redundancy analysis (RDA) showed that soil microbial biomass and structure explained 43.0% (R2 = 0.53) of the total variation in Pb uptake by B. campestris, compared to 9.51% of microbial activity. G- bacteria explained 23.2% of the total variation in the Pb uptake by B. campestris, significantly higher than the other microbes. The Mantel test showed that microbial properties significantly influenced Pb uptake by B. campestris under the driving force of earthworms. E. fetida inoculation was favorable for the G- bacterial community, whereas A. aspergillum inoculation was favorable for the fungal community. Both microbial communities facilitated the entry of Pb into the vegetable food chain system. This study delivers novel evidence and meaningful insights into how earthworms prime the microbial mechanism of Pb uptake by leafy vegetables by influencing soil microbial biomass and community composition. Comprehensive metagenomics analysis can be employed in future studies to identify the microbial strains promoting Pb migration and develop effective strategies to mitigate Pb contamination in food chains.

Microbial-earthworm ecofilters (MEES) for urban wastewater treatment

Water is an absolute necessity for life and water scarcity is a major problem all over the world. Reusing household wastewater for non-potable water applications is one of the solutions to tackle this problem. Many developing countries lack the technological resources to construct and operate costly wastewater treatment plants. They need cost-effective wastewater treatment options so that both economic aspects and human needs can be met easily. Centralized sewage treatment systems are unable to achieve future demands for sustainable wastewater management in developing countries due to the growing population and needs. The present work examines the effectiveness of treating urban wastewater with microbial-earthworm eco filters (MEEs) (reactor 2) and the filter unit without earthworms (reactor 1). Results of the use of the vermi-biofiltration wastewater treatment unit comprising the biological filtration treatment unit, Eisenia fetida earthworm species, live soil organisms, and natural stones to treat household wastewater are reported herein. The biological oxygen demand (BOD), total dissolved solids (TDS), chemical oxygen demand (COD), and total organic carbon (TOC) were monitored for seven weeks. These parameters exhibited a decreasing trend in both the filtration units. A 75 % reduction in TOC for reactor 2 shows the effectiveness of the proposed system for the utilization of wastewater from urban households. Reactor 2 also showed a reduction in BOD, COD, and TDS approximately in the range of 85, 90, and 30 % respectively. This technique seems to be useful for developing a low-cost and useful household purification system in water-scarce areas using harmless bio-organisms.

Understanding the diversification and functional radiation of Aporrectodea (Crassiclitellata, Lumbricidae) through molecular phylogenetics of its endemic species

The genus Aporrectodea includes some of the most conspicuous earthworm species, but its taxonomic history is among the most complex within the family Lumbricidae. Molecular phylogenetic studies have produced some advances by assigning former Aporrectodea species to other monophyletic clades and by detecting species level lineages within the cosmopolitan caliginosa-trapezoides complex. However, little attention has been devoted to endemic taxa of Aporrectodea such as Ap. rubra, Ap. arverna, Ap. gogna, Ap. balisa, Ap. velox, Ap. giardi voconca and Ap. longa ripicola. These earthworms (and additional populations of Ap. longa and Ap. nocturna) were included in a molecular phylogenetic framework in order to reconstruct the ancestral range of the genus, as well as to help understand its diversification within its native range and to perform a systematic revision. Species delimitation, ancestral area reconstruction and Bayesian inference of the phylogenetic relationships were performed using a large gene sequence (COI) dataset and a narrower dataset composed of 5 mitochondrial and nuclear markers. Phylogenetic position and species delimitation indicated that Ap. giardi voconca and Ap. longa ripicola constitute species-level entities not closely related to Ap. giardi or Ap. longa, and they were thus redescribed as Aporrectodea voconca stat. nov. and Aporrectodea ripicola stat. nov. Ancestral area reconstruction enabled location of the origin of Aporrectodea in the Auvergne-Rhône-Alps, in Southeastern France. The study findings provide some insight into the evolution of functional traits in this ecologically successful genus. Ap. rubra and Ap. arverna (small, reddish, epigeic/epianecic) and Ap. gogna (very large, dark, anecic) were recovered as the earliest branching taxa, suggesting a complex evolution of functional traits within this genus.

Earthworms from soils developed after 80 years under tree monocultures at Holt Down, Hampshire, UK

Experimental research from the 1980s showed that tree species influenced soil development where stands of beech (Fagus sylvatica) and small-leaved lime (Tilia cordata) respectivey started to develop a podzolic soil and a brown forest soil after 50 years from near identical origins. Evidence of earthworms was reported but no detail provided. Current work re-examined these soils and a further adjacent spruce (Picea abies) plantation and specifically sampled for earthworms. Standard soil and litter measurements were made, and earthworms were collected by a combined digging and hand-sorting, plus vermifuge technique. The soil surface below lime was covered with Mercurialis perennis, but deep leaf litter was present below beech, with needle cover below spruce. Significantly more earthworms were present below lime, at a density of 29 m−2, when compared with beech (<2 m−2) with spruce intermediate (11 m−2), with a significantly greater earthworm biomass below lime. Of 8 earthworm species collected, more than 70% were from below lime, including Aporrectodea longa, Lumbricus terrestris, A. caliginosa, Octolasion cyaneum and L. rubellus. Those below spruce were mainly Dendrobaena octaedra and only A. longa was found below beech. These observations, after 80 years of differential soil development below tree stands, clearly show continued interactive influences on soils of monoculture tree species with associated ecosystem engineering earthworms.

A Comprehensive Study on Agricultural Residue Management by Vermicomposting

The green revolution as well as improved seed-based fertilizers and water management have increased food grain production. The planned crop has led to an increase in food grains and biodiversity. Rice farming, wheat production as well as sugarcane crops have also increased the yield and crop waste. This farm waste has also increased the cost of farm management. Many farmers’ burn and dispose of this waste, which causes air pollution. For example, the burning of waste from paddy and wheat farms in Punjab has led to an increase in air pollution in and around New Delhi. Also, the burning of farm waste is causing the loss of organic matter. Therefore, the vermicomposting project is the right way to use all such agricultural waste in the same field. This will enable proper drainage of field waste and enable the concerned farmer to produce vermicomposting containing the maximum amount of Nitrogen, Phosphorus, and Potash in less space. Therefore, while maintaining the balance of the environment, natural air, and water remain clean. Varieties of earthworm species are utilized for making vermicompost, which is useful for the rapid growth of a crop. This reduces the use of chemical fertilizers in the field and enables the farmers to do properly planned farming at a low cost. It takes less time to do vermicomposting. They also make the seedlings grow faster, Increases soil water holding capacity, and Reduce soil BOD. Also, vermicomposting is a boon for the nursery. Stakeholders would be truly intelligent consumers.

Filling Gaps in Earthworm Digital Diversity in Northern Eurasia from Russian-language Literature

Data availability for certain groups of organisms (ecosystem engineers, invasive or protected species, etc.) is important for monitoring and making predictions in changing environments. One of the most promising directions for research on the impact of changes is species distribution modelling. Such technologies are highly dependent on occurrence data of high quality (Van Eupen et al. 2021). Earthworms (order Crassiclitellata) are a key group of organisms (Lavelle 2014), but their distribution around the globe is underrepresented in digital resources. Dozens of earthworm species, both widespread and endemic, inhabit the territory of Northern Eurasia (Perel 1979), but extremely poor data on them is available through global biodiversity repositories (Cameron 2018). There are two main obstacles to data mobilisation. Firstly, studies of the diversity of earthworms in Northen Eurasia have a long history (since the end of the nineteenth century) and were conducted by several generations of Soviet and Russian researchers. Most of the collected data have been published in "grey literature", now stored only in a few libraries. Until recently, most of these remained largely undigitised, and some are probably irretrievably lost. The second problem is the difference in the taxonomic checklists used by Soviet and European researchers. Not all species and synonyms are included in the GBIF (Global Biodiversity Information Facility) Backbone Taxonomy. As a result, existing earthworm species distribution models (Phillips 2019) potentially miss a significant amount of data and may underestimate biodiversity, and predict distributions inaccurately. To fill this gap, we collected occurrence data from the Russian language literature (published by Soviet and Russian researchers) and digitised species checklists, keeping the original scientific names. To find relevant literature, we conducted a keyword search for "earthworms" and "Lumbricidae" through the Russian national scientific online library eLibrary and screened reference lists from the monographs of leading Soviet and Russian soil zoologist Tamara Perel (Vsevolodova-Perel 1997, Perel 1979). As a result, about 1,000 references were collected, of which 330 papers had titles indicating the potential to contain data on earthworm occurrences. Among these, 219 were found as PDF files or printed papers. For dataset compilation, 159 papers were used; the others had no exact location data or duplicated data contained in other papers. Most of the sources were peer-reviewed articles (Table 1). A reference list is available through Zenodo (Ivanova et al. 2023). The earliest publication we could find dates back to 1899, by Wilhelm Michaelsen. The most recent publication is 2023. About a third of the sources were written by systematists Iosif Malevich and Tamara Perel. Occurrence data were extracted and structured according to the Darwin Core standard (Wieczorek et al. 2012). During the data digitisation process, we tried to include as much primary information as possible. Only one tenth of the literature occurrences contained the geographic coordinates of locations provided by the authors. The remaining occurrences were manually georeferenced using the point-radius method (Wieczorek et al. 2010). The resulting occurrence dataset Earthworm occurrences from Russian-language literature (Shashkov et al. 2023) was published through the Global Biodiversity Information Facility portal. It contains 5304 occurrences of 117 species from 27 countries (Fig. 1). To improve the GBIF Backbone Taxonomy, we digitised two catalogues of earthworm species published for the USSR (Perel 1979) and Russian Federation (Vsevolodova-Perel 1997) by Tamara Perel. Based on these monographs, three checklist datasets were published through GBIF (Shashkov 2023b, 124 records; Shashkov 2023c, 87 records; Shashkov 2023a, 95 records). Now we work towards including these names in the GBIF Backbone so that all species names can be matched and recorded exactly as mentioned in papers published by Soviet and Russian researchers.

Pesticide effect on earthworm lethality via interpretable machine learning

Earthworms are among the most important animals (invertebrates) for soil health. Many chemical substances released into nature for agricultural development, such as pesticides, may have unwanted effects on those organisms. However, it is essential to understand the extent of the impact of chemicals on soil health first and then make the proper decisions for regulatory or commercial purposes. We hypothesize that there is an expressible quantitative structure-activity relationship (QSAR) between the structure of pesticide compounds and the acute toxicity effect of earthworm species Eisenia fetida. The description of this relationship allows for a better assessment of the impact of chemicals on the said earthworm. To describe this relationship, a dataset of chemicals was collected from open-access sources to develop a mathematical model. A novel approach, combining genetic algorithm and Bayesian optimization, was used to select structural features into the model and to optimize model parameters. The final QSAR classification model was created with the Random Forest algorithm and exhibited good prediction Accuracy of 0.78 on training set and 0.80 on test set. The model representation follows FAIR principles and is available on QsarDB.org.

Vermicast Analysis with the Earthworm Species Pheretima losbanosensis (Crassiclitellata: Megascolecidae): Bacterial Profiles for Potential Applications in Agriculture

In the Philippines, the use of non-native earthworm species in vermicomposting is popular. Given that the country is a vital geographical resource for earthworm diversity, the study of earthworm species to establish the potential of their vermicasts in agricultural applications is essential. In this study, the bacteria associated with the vermicasts of the recently described indigenous species, Pheretima losbanosensis, were investigated using next-generation sequencing, community-level physiological profiling, and NPK activity screening. The results showed diverse bacterial species belonging to the phyla Proteobacteria, Bacteroidetes, Acidobacteria, Actinobacteria, Chloroflexi, Firmicutes, Gemmatimonadetes, Nitrospirae, Planctomycetes, Spirochaetes, Thermodesulfobacteria, and Verrucomicrobia. Higher diversity and carbon substrate utilization (p &lt; 0.05) of amines and amides, phenolic compounds, polymers, and carboxylic and acetic acids were exhibited by the bacterial communities of P. losbanosensis compared to those of Eudrilus eugeniae. Likewise, bacteria (n = 25) isolated from P. losbanosensis vermicasts had higher nitrogen fixation and phosphate and potassium solubilization activities (p &lt; 0.05) than the bacteria (n = 20) isolated from E. eugeniae vermicasts. Overall, our results indicate that the diverse bacterial communities inhabiting the vermicasts of P. losbanosensis have nutrient mineralization and carbon substrate utilization activities that may have applications in sustainable agriculture as a potential organic input to promote plant growth and improve soil substrate.

Earthworms reduce nutrient loss from loess soil slopes under simulated rain

Burrowing, feeding, and casting activities of earthworms affect nutrient cycling and hydrological processes that take place in sloping lands. However, the effects exerted by earthworms on nutrient losses associated with runoff and sediment during rain remains unclear, particularly in the Loess Plateau, where soil erosion and nutrient loss have led to severe environmental issues. In this study, our purpose was to quantify the effects exerted by the anecic earthworm species, Metaphire guillelmi, on nutrient loss via runoff and erosion in loess soil slopes. Six artificial grass slopes (mesocosms, 15°), comprising three with earthworms (100 individuals m−2) for 28 days, and three without earthworms, were subjected to simulated rain (90 mm h−1) for 60 min. Our results indicated that earthworms had (i) increased the content of NO3–-N from 8.1 to 151.8 mg kg−1 and OP from 51.0 to 71.8 mg kg−1, but decreased the content of OC from 6.6 to 5.2 g kg−1, TN from 0.76 to 0.62 g kg−1, TP from 0.73 to 0.68 g kg−1 and NH4+-N from 3.7 to 2.4 mg kg−1 at surface 2 cm soil; (ii) increased water-stable macroaggregates from 45.1 to 48.3% and soil saturated water conductivity from 0.07 to 0.28 mm min−1, and (iii) greatly reduced the cumulative runoff from 65.7 to 15.3 mm and sediment occurance from 0.44 to 0.16 kg m−2 on slopes. Consequently, earthworm activities decreased runoff-associated nutrients (decreased NH4+-N from 19.5 to 2.8 mg m−2, NO3–-N from 108.2 to 26.2 mg m−2, and SP from 2.2 to 0.1 mg m−2) loss by 75.8–96.2%, and sediment-bound nutrient (decreased OC from 2.4 to 0.8 g m−2, TN from 0.3 to 0.1 g m−2, TP from 0.3 to 0.1 g m−2) loss by 63.8–68.5%. Hierarchical partitioning and variation partitioning analyses showed that runoff and sediment yields and their interaction with the soil physical characteristics were the dominant pathways via which earthworms regulated nutrient loss during rainfall events. This study highlights the importance of soil fauna in regulating erosion and nutrient loss in the Loess Plateau, and indicates that these factors should be considered in future water and soil conservation management.

Checklist of the earthworm fauna (Oligochaeta: Lumbricidae) of Uzbekistan

Abstract. Abdullaev I, Bekchanova M, Gandjaeva L, Kholmatov B, Raxmatullayev A, Tajiyev Z, Razzakov K, Matyakubov Z, Doschanova M, Ruzmetov R. 2023. Checklist of the earthworm fauna of Uzbekistan (Oligochaeta: Lumbricidae). Biodiversitas 24: 4392-4401. This article presents a checklist of the earthworm fauna (Lumbricidae) of Uzbekistan based on published records and the authors' data. This is the first checklist for Uzbekistan, which contains complete information on the ecological category, habitat, type of distribution and distribution of 28 species of earthworms in 4 regions of Uzbekistan. The currently known, based on our research, earthworm fauna of Uzbekistan, includes 23 species, 5 subspecies belonging to 9 genera. Of them, 3 species (Perelia persiana, Perelia turcmenica, Lumbricus rubellus) are new to Uzbekistan. Perelia is the species-richest genus (12 species). These earthworms are distributed Kyzylkum desert region along river banks, in the mountainous regions of Pomiro Alai and Tien Shan biogeographic region, which is mostly covered with forest or autochthonous flora. The earthworm fauna is more diverse in forests of the northern and in the mountains of the southern parts of Uzbekistan. Literature data and our present study showed that there are no earthworms in the Ustyurt Plateau, due to the fact that the soils of the Ustyurt Plateau are gypsum, saline, and infertile.

Biology of the epigeic earthworm, Eisenia fetida in different organic wastes

Aim: A study was undertaken to know the influence of different organic wastes on the biology of the epigeic earthworm, Eisenia fetida. Methodology: Epigeic earthworm, Eisenia fetida was selected and collected. Organic wastes (Corn stover, Delonix regia and Eichhornia crassipes) which are abundant and locally available were collected and used as feed materials along with cattle manure as control in this experiment. Results: The minimum incubation period and the maximum number of hatchlings per cocoon were observed in cattle manure (Control) as compared to other organic wastes. Percent cocoon hatching was 100% in all organic wastes, including control. The weight of freshly emerged juvenile was almost same in all organic wastes with no significant variations. The worm biomass was maximum in Eichhornia crassipes, whereas growth rate, attainment of sexual maturity and rate of cocoon production was maximum in cattle manure followed by other organic wastes. Interpretation: A successful vermitechnological process not only depends on the type of organic waste, but also depends on the biology of earthworm species. Based on the results, it can be concluded that epigeic earthworm, Eisenia fetida can be efficiently used in the vermitechnological process for organic waste management so as to maintain the balanced ecosystem. Key words: Eisenia fetida, Epigeic earthworm, Organic wastes, Vermicompost, Worm biology

Vermistabilization of mango tree pruning waste with five earthworm species: A biochemical and heavy metal assessment

Mango tree pruning results in high biomass output, which is a serious agricultural and environmental problem. Vermicomposting is a potential, fast and sustainable tool to address these challenges. For sixty days, the experiment was carried out in six vermireactors containing five earthworm species by Eudrilus eugeniae, Eisenia fetida, Aporrectodea rosea, Lumbricus rubellus, and Lampito mauritii, as well as composting (without earthworm) using mango tree pruning waste biomass along with cattle dung as an instant preferred feeding material for earthworms. The pH, TOC, C/N and C/P ratios of the waste were substantially reduced by the earthworm activity. However, after vermicomposting, the levels of macronutrients (N, P, K, Ca, Mg, S) and micronutrients (Fe, Mn, Zn, and Cu) and microbial count substantially increased. The TOC content of waste was reduced by 42–55%, and the C/N of vermicompost ranged from 5.58 to 11.38. The results showed that earthworm fecundity was highest in vermireactors containing Eudrilus eugeniae and Eisenia fetida. The current study was ultimately determine that vermicomposting using Eudrilus eugeniae or Eisenia fetida is an effective strategy for utilising mango tree pruning waste, ensuring environmental sustainability and improving farmer revenue.

Gut microbial communities and their potential roles in cellulose digestion and thermal adaptation of earthworms

Adaptations to temperature and food resources, which can be affected by gut microbiota, are two main adaptive strategies allowing soil fauna to survive in their habitats, especially for cold-blooded animals. Earthworms are often referred to as ecosystem engineers because they make up the biggest component of the animal biomass found in the soil. They are considered as an important indicator in the triangle of soil quality, health and functions. However, the roles of gut microbiota in the environmental adaptation of earthworms at a large scale remain obscure. We explored the gut bacterial communities and their functions in the environmental adaptation of two widespread earthworm species (Eisenia nordenskioldi Eisen and Drawida ghilarovi Gates) in Northeast China (1661 km). Based on our findings, the alpha diversity of gut bacterial communities decreased with the increase of latitude, and the gut bacterial community composition was shaped by both mean annual temperature (MAT) and cellulose. Actinobacteria, Proteobacteria, Firmicutes, and Planctomycetes, recognized as the predominant cellulose degraders, were keystone taxa driving gut bacterial interactions. Actinobacteria, Firmicutes, and Planctomycetes were influenced by MAT and cellulose, and had higher contributions to gut total cellulase activity. The optimal temperature for total cellulase in the gut of E. nordenskioldi (25-30 °C) was lower than that of D ghilarovi (40 °C). The gut microbiota-deleted earthworms had the lowest cellulose degradation rate (1.07 %). The cellulose was degraded faster by gut bacteria from the host they were derived, indicating the presence of home field advantage of cellulose decomposition. This study provides a foundation for understanding the biotic strategies adopted by earthworms when they enter a new habitat, with gut microbiota being central to food digestion and environmental adaptability.

Variability of earthworm's functional traits in eastern Amazon is more species-dependent than environment-dependent

Understanding the causes of variability in functional traits is an important question in earthworm ecology. While interspecific variation in anatomical dimensions for the same trait is well accepted, the role of environmental filters, soil degradation, and environmental stress in affecting the variability of functional traits is not well understood. In this study, we sought to determine the relative importance of environmental factors and earthworm species taxonomy on the variability in functional traits within species (intraspecific variability). We focused on eight functional traits including body mass, body length, body diameter, gizzard, gizzard thickness, septum thickness, typhlosole, and gut organic matter. We sampled earthworms of 11 different species in various regions of the eastern Amazon to determine the general responses of different species' characteristics when exposed to various ecosystem and soil conditions. Our results suggest that the functional traits of earthworms are influenced in different ways by environmental conditions. One set of traits, including body mass, body length, and body diameter, was more constant and independent of environmental variability, while another set, including gizzard diameter and length, gizzard muscle thickness, septum thickness, typhlosole, and intestinal organic matter, was more sensitive. The most affected by different environmental variables was septum thickness. We also examined which environmental factors are most important for trait variability. Our study highlights the importance of considering both environmental factors and taxonomic classification when studying the variability of functional traits within earthworm species. Overall, our results suggest that taxonomic classification alone is a good guide for estimating the major functional traits of earthworms in the Brazilian Amazon, but local conditions can their variability is which is essential for informing conservation efforts and maintaining ecosystem function.

The effects of Eisenia fetida and Metaphire guillelmi on the soil micro-food web in a microcosm experiment.

Numerous studies have shown that the function of earthworms may depend on their ecotype and density, which affects how they impact soil microbial and nematode communities. However, it is unclear how different earthworm species and densities alter the composition of soil microbial and nematode communities and how these modifications impact the soil micro-food web. The structural equation model (SEM) is a more accurate tool for identifying the intricate relationships between various trophic levels in the soil micro-food webs than the widely used bivariate data analysis. In order to ascertain the effects of earthworm species, including epigeic earthworm Eisenia fetida and anecic earthworm Metaphire guillelmi, as well as varying densities on the composition of main microbial groups, soil nematodes and their relationships, a microcosm experiment was conducted in a greenhouse. After nine weeks of observation, compared with the control treatments, Eisenia fetida increased the biomasses of total microorganism and bacteria, whereas Metaphire guillelmi decreased the biomasses of total microorganism, bacteria, and gram-positive bacteria, but showed an increase in AMF biomass. Additionally, both two earthworm species decreased the abundance of total soil nematode, bacterivores, and omnivore-predators, which is in contrast with the control treatments. The SEM results indicated that the addition of Eisenia fetida at different densities had indirect negative effects on the abundance of omnivore-predators, as it significantly increased the content of soil organic carbon, ammonium nitrogen, and nitrate nitrogen. The bottom-up effects were found to be the dominant forces, which promoted bacterial-dominated decomposition channels. The addition of Metaphire guillelmi with different density had direct negative impact on bacterivores and fungivores. Moreover, it had indirect negative effects on omnivore-predators by altering the soil properties. The dominant forces were still the bottom-up effects. Our study suggests that different earthworm species have distinct mechanisms that affect the soil micro-food web in different ways.

Can antimony contamination in soil undermine the ecological contributions of earthworms?

As antimony (Sb) has been increasingly used in manufacturing industries (e.g., alloy, polymer and electronics industries), Sb contamination in the soil environment becomes widely reported and has drawn growing attention due to the toxicity of Sb to living organisms. Whether soil-dwelling organisms can tolerate Sb toxicity and maintain their ecological functions remains poorly understood. Using a cosmopolitan, ecologically important earthworm species (Eisenia fetida) as an ideal model organism, we examine the effects of Sb on the physiological, molecular and behavioural responses of earthworms to different levels of Sb contamination in soil (0, 10, 50, 100, 250 and 500 mg/kg). We found that earthworms could tolerate heavy Sb contamination (100 mg/kg) by boosting their antioxidant defence (POD and GST) and immune systems (ACP) so that their body weight and survival rate were sustained (c.f. control). However, these systems were compromised under extreme Sb contamination (500 mg/kg), leading to mortality. As such, earthworms exhibited avoidance behaviour to escape from the Sb-contaminated soil, implying the loss of their ecological contributions to the environment (e.g., increase in soil aeration and maintenance of soil structure). By measuring various types of biomarkers along a concentration gradient, this study provides a mechanistic understanding of how earthworms resist or succumb to Sb toxicity. Since extreme Sb contamination in soil (>100 mg/kg) is rarely found in nature, we are optimistic that the health and performance of earthworms are not influenced by Sb in most circumstances, but regular monitoring of Sb in soil is recommended to ensure the integrity and functioning of soil environment. Further studies are recommended to evaluate the long-term impact of Sb in the soil ecosystem through bioaccumulation and trophic transfer among soil-dwelling organisms.

Ovary organization and ultrastructure in six species of Amynthas and Metaphire earthworms (Annelida, Crassiclitellata, Megascolecidae)

Ovaries in earthworms belonging to the family Megascolecidae are paired structures attached to the septum in the anterior part of the XIII segment. They are fan to rosette shaped with numerous rows of growing oocytes, known as egg strings, radiating from the ovary center towards the segmental cavity. The histological and ultrastructural ovary organization in megascolecids and the course of oogenesis remain unknown. The paper presents the results of light and electron microscopy analyses of ovaries in six megascolecid species, three from the genus Amynthas and three from Metaphire. Both parthenogenetic and sexually reproducing species were included in the study. The organization and ultrastructure of ovaries in all studied species are broadly similar. Considering the histological organization of ovaries, they could be divided into two zones. Zone I (proximal, close to the connection with the septum) is tightly packed with germline and somatic cells. Germ cells are interconnected via intercellular bridges and thin strands of the central cytoplasm (known as cytophore) and form syncytial cysts. Cysts unite oogonia, early meiotic cells (till diplotene), and clustering cells develop synchronously. During diplotene, interconnected cells lose developmental synchrony; most probably, one cell per cyst grows faster than others, detaches from the cysts, and becomes an oocyte. The remaining cells grow slightly and are still interconnected via the thin and reticular cytophore; these cells are considered nurse cells. Zone II has a form of egg strings where growing oocytes are isolated one from another by thin somatic cells and form short cords. We present the ultrastructural details of germline and somatic cells. We propose the term "Amynthas" type of ovaries for this ovary organization. We suppose that such ovaries are characteristic of other megascolecids and related families.

Bioaccumulation of pesticide residue in earthworms collected from the agricultural soils of Kuttanad-a unique agroecosystem in India.

Earthworms encompass significant soil faunal biomass and have tremendous potential to provide vital ecosystem services. Earthworms are considered bioindicators of chemical contaminants and can provide early warnings of ecosystem deterioration. Studies pertaining to the accumulation of pesticide residues in earthworm in biomass in agrarian ecosystems are scarce. The Kuttanad agroecosystem (KAE), situated on the southwest coast of India, is one of the few regions globally supporting farming on land below the mean sea level. This investigation was conducted to assess the bioaccumulation of pesticide residues in earthworms from the KAE. The earthworms species Glyphidrilus annandalei collected from agricultural soils of the study area were analyzed for the presence of pesticides residues such as α-BHC, γ-BHC, atrazine, heptachlor, α-chlordane, γ-chlordane, 4,4-DDE, 4,4-DDD, 4,4-DDT, β-endosulfan, and endrin ketone in their biomass. Analysis of the earthworm samples using a gas chromatograph revealed the presence of ten pesticide residues with notable concentrations (α-BHC, 0.36ng/g; γ-BHC, 0.41ng/g; heptachlor, 0.10ng/g; atrazine, 0.89ng/g; α-chlordane, 0.07ng/g; γ-chlordane, 0.10ng/g; 4,4-DDE, 0.05ng/g; 4,4-DDD, 0.11ng/g; 4,4-DDT, 0.31ng/g; β-endosulfan, 0.19ng/g; and endrin ketone, 0.13ng/g). Six groups of pesticide residues are ΣBHC, ΣDDT, atrazine, Σchlordane, endrin ketone, and β-endosulfan were observed during bioaccumulation factor analysis, and the results show the following trend: atrazine > ΣBHC > ΣDDT > Σchlordane > Σendosulfan > Σendrin. As earthworms are a crucial component of this region's food chains, bioaccumulation of pesticide residues in earthworms can pause adverse consequences. Increasing trends in pesticide application in the KAE and bioaccumulation of pesticide residues in earthworm biomass can affect the entire food web.

Earthworms neutralize the influence of components of particulate pollutants on soil extracellular enzymatic functions in subtropical forests.

Human activities are increasing the input of atmospheric particulate pollutants to forests. The components of particulate pollutants include inorganic anions, base cations and hydrocarbons. Continuous input of particulate pollutants may affect soil functioning in forests, but their effects may be modified by soil fauna. However, studies investigating how soil fauna affects the effects of particulate pollutants on soil functioning are lacking. Here, we investigated how earthworms and the particulate components interact in affecting soil enzymatic functions in a deciduous (Quercus variabilis) and a coniferous (Pinus massoniana) forest in southeast China. We manipulated the addition of nitrogen (N, ammonium nitrate), sodium (Na, sodium chloride) and polycyclic aromatic hydrocarbons (PAHs, five mixed PAHs) in field mesocosms with and without Eisenia fetida, an earthworm species colonizing forests in eastern China. After one year, N and Na addition increased, whereas PAHs decreased soil enzymatic functions, based on average Z scores of extracellular enzyme activities. Earthworms generally stabilized soil enzymatic functions via neutralizing the effects of N, Na and PAHs addition in the deciduous but not in the coniferous forest. Specifically, earthworms neutralized the effects of N and Na addition on soil pH and the effects of the addition of PAHs on soil microbial biomass. Further, both particulate components and earthworms changed the correlations among soil enzymatic and other ecosystem functions in the deciduous forest, but the effects depended on the type of particulate components. Generally, the effects of particulate components and earthworms on soil enzymatic functions were weaker in the coniferous than the deciduous forest. Overall, the results indicate that earthworms stabilize soil enzymatic functions in the deciduous but not the coniferous forest irrespective of the type of particulate components. This suggests that earthworms may neutralize the influence of atmospheric particulate pollutants on ecosystem functions, but the neutralization may be restricted to deciduous forests.

Vermitechnology: A Sustainable Approach to Manage Organic Waste in Urban Areas

Vermicomposting is the natural process of compost formation by converting organic wastes into organic fertiliser utilising earth worms and cow dung. It is being widely used for solid waste management. Many species of earthworms are utilised in this process such as Eisenia fetida, Eudrilus eugeniae, Eisenia andrei, Lampito rubellus and Drawida willis. They feed on the organic waste to produce vermicompost, vermiwash and more earthworms as resultant products. Composting process with this technique takes around 28-120 days and it depends upon the type of worms and organic waste used. Kirori Mal College of the University of Delhi is pioneer in adopting the vermicomposting on a large scale. It has put 15 beds in place in its nursery. This set of fifteen composting beds is able to utilise about 1.7 tons of dry leaves in a single cycle and converts them into very nutritious fertilizer. As we could run four such cycles in a year, the Kirori Mal College has the potential of consuming about seven tons of dry leaves annually and put it to a better use, which otherwise, would have been a responsibility of the Municipal Corporation of Delhi. Along with the vermicompost, the process also produces vermiwash, a concentrated liquid fertilizer, which is stored and is being utilized after dilution. The vermicomposting also leads to rapid multiplication of earthworms, which can be sold in the market and the spare ones can be utilised for the next cycle. Vermicomposting for the disposal of the dry organic waste is very cost effective and energy efficient.