Search

Abstract: The effect of earthworms on humus composition and humic acid (HA) characteristics was studied in a rice–wheat rotation agroecosystem. Experimental plots in the rotation had five treatments, i.e., incorporation or mulching of maize residues with or without added earthworms and a control. Compared with the control, the application of maize residues to soil either alone or in combinations with earthworms strongly affected the humus composition and HA characteristics. In the presence of earthworms, the carbon ratio of HA to fulvic acid (FA), and the alkyl C/O-alkyl C and hydrophobic C/hydrophilic C ratios of HA were slightly higher, while the aliphatic C/aromatic C ratio of HA was slightly lower following maize residue incorporation than the same treatment without earthworms. In contrast, these ratios generally remained almost constant following maize residue mulching. Thus, earthworm activity following maize residue incorporation was more favorable for the HA formation, and was associated with a decrease in aliphaticity of HA, and an increase in its degree of humification and hydrophobicity. [Copyright &y& Elsevier]

A hydroponic experiment was carried out to study the effects of earthworm (Metaphire guillemi) mucus on tomato Hezuo 903 (Lycopersicon esculentum) seedlings growth and cadmium (Cd) accumulation. The experiment included three levels of Cd addition rates (0, 5 and 10 mg L-1), two levels of earthworm mucus addition (20 and 40 ml per pot) treatments (EML and EMH), and the control (CK). The results showed that compared with the control, earthworm mucus addition significantly increased shoot and root dry weights of tomato seedling by 13.8-44.5% and 12.4-33.2%, respectively. In contrast, high earthworm mucus addition (EMH) led to a 4% shoot weights decrease at 10 mg Cd L-1 compared with CK. Cadmium concentrations and accumulations in both shoot and root of tomato seedlings were significantly increased (p < 0.01) with increasing Cd and earthworm mucus addition levels. Cadmium concentrations and accumulations in root were much higher than those in corresponding shoot. Present study indicated that earthworm mucus could enhance tomato seedlings growth and Cd accumulation. Our work might be not only very useful for understanding how earthworms enhance plant growth and heavy metals accumulation, but also for further application of earthworms in phytoextraction. [ABSTRACT FROM AUTHOR]

In order to investigate the basic mechanism of earthworm activities enhancing plants growth and heavy metals accumulations. A hydroponic experiment was carried out to investigate the effects of earthworm mucus and mimic amino acids solution of earthworm mucus on cadmium (Cd) subcellular distributions and chemical forms in tomato seedlings. The result showed that earthworm mucus significantly increased the concentrations of Cd stored in soluble fraction in subcellular distribution and the concentrations of inorganic and soluble forms of Cd in tomato seedlings, which may explain the increase plants growth and Cd accumulation by earthworm mucus. Meanwhile, amino acids have same function as earthworm mucus, but the effect was much lower than of earthworm mucus. These results indicated that earthworm mucus could increase tomato seedlings growth and Cd accumulations through changing Cd subcellular distribution and chemical forms in plants. [Copyright &y& Elsevier]

Earthworms naturally secrete substantial amounts of mucus (relative to their body size) from the cuticle when moving through the soil. However, how the metabolites in the epidermally derived mucus affect soil microfauna is largely unknown. The objective of this study was to determine how earthworm mucus affected the physiology of the model nematode Caenorhabditis elegans and that of two soil-dwelling bacterial-feeding nematodes: Mesorhabditis sp. and Protorhabditis sp. The traits examined included phobotaxis, reproduction, mortality, body size, feeding inhibition rate, and feeding preference. Two nematode species escaped from the earthworm mucus, whereas earthworm mucus reduced the reproduction of C. elegans and increased the mortality of C. elegans and Mesorhabditis sp. Moreover, earthworm mucus reduced the feeding rate of C. elegans and Protorhabditis sp. and changed the feeding preferences of all three species of nematodes. At 48 h, earthworm mucus increased feeding on Bacillus amyloliquefaciens JX1 for C. elegans and Protorhabditis sp. and reduced feeding on Escherichia coli OP50 for Mesorhabditis sp. These results suggest that earthworm mucus can be detrimental to bacterial-feeding nematodes and provide insights into the non-trophic interactions between earthworms and other soil biota. • Two of the three bacterial-feeding nematodes escaped from earthworm mucus. • Earthworm mucus reduced the reproduction of C. elegans. • Earthworm mucus increased the mortality of the C. elegans and Mesorhabditis sp. • Earthworm mucus inhibited the feeding rate of C. elegans and Protorhabditis sp and changed the feeding preferences of all the bacterial-feeding nematodes. [ABSTRACT FROM AUTHOR]

As ubiquitous ecosystem engineers, earthworms play an important role in shaping the architecture and functioning of soil systems. However, there is limited knowledge on how earthworms modify the soil microbiome in relation to soil biogenic aggregates, hot-spots formed by earthworms, especially in agricultural systems. We investigated microbial communities in physical fractions and bulk soil from an arable field with consecutive rice - wheat cropping after manipulating earthworms and organic amendments for 13 years. Earthworms significantly enhanced soil aggregation by 33.4% across two consecutive cropping seasons. The assemblage of bacterial communities varied strongly between soil aggregate fractions and with earthworm presence, while the assemblage of fungal communities varied most with organic amendments and less between aggregate fractions. Structural equation modelling (SEM) suggests that besides direct effects on bacteria and fungi, earthworms affected bacteria indirectly via increasing soil aggregation (MWD), but mediated fungi via lowering pH, indicating that the role of soil aggregates in structuring soil bacterial communities override that of resource availability. In conclusion, results of our over-decade field experiment suggest that earthworms modify soil microbial communities primarily through mediating soil habitat architecture and affecting resource supply. • A long-term study explored earthworm impacts on aggregate-associated microbiome. • Earthworms increase soil macro-aggregates (>2 mm) formation. • Earthworms modify soil bacterial community mainly via stimulating soil aggregation. • Earthworms modify soil fungal community mainly via changing chemical properties. [ABSTRACT FROM AUTHOR]

Benzo[a]pyrene (BaP) and cadmium (Cd) are soil pollutants that persist in the environment and impacting soil health. Earthworms are selective consumers, yet little is known about how their feeding and burrowing habits translate into species-specific differences in pollution accumulation and distribution. Here, we exposed three ecophysiologically distinct earthworm species, Eisenia fetida (epigeic), Pheretima guillelmi (endogeic), and Metaphire guillelmi (anecic) to different concentrations (0, 1, 10, 30, 60, 100, 300, 500 mg/kg) of BaP or Cd in natural fluvo–aquic soil for 14 days. BaP and Cd accumulation and distribution patterns were analyzed at the individual and organ levels. The results showed that the adsorption behavior of BaP or Cd in earthworms and the organs fit the Langmuir adsorption model well (R 2  > 0.8, p  < 0.001). E. fetida and M. guillelmi accumulated more BaP than Cd, with the respectively higher predicted maximum internal concentration (C max ) of BaP (1946.27 ± 306.29 mg/kg, 2046.61 ± 90.64 mg/kg) and the lower C max of Cd (279.75 ± 49.57 mg/kg, 318.11 ± 60.64 mg/kg), while P. guillelmi showed the opposite trend with 927.10 mg/kg of Cd C max and 358.82 ± 68.35 mg/kg of BaP C max . The low mobility of endogeic worms may reduce their BaP accumulation, and lead to a lower BaP bioaccumulation factor (BAF) than that observed for the other two earthworms; P. guillelmi had a BAF of 8.64 ± 1.79, which was far less than that of E. fetida (106.93 ± 11.84) and M. guillelmi (350.16 ± 67.15). Whereas the higher Cd accumulation in P. guillelmi may be due to their highly efficient geophagous feeding strategy, at the same time the highest Cd BAF achieved (e.g. 203.54 ± 19.96 under 1 mg/kg Cd exposure). BaP distributed mainly in the body walls of all three earthworms (average 60.78%), as its high hydrophobicity increased its dermal uptake. More BaP than Cd accumulated in the reproductive organs, and C max of BaP in E. fetida , P. guillelmi, and M. guillelmi in the reproductive organs was 4031.08 ± 1237.38 mg/kg, 490.76 ± 79.88 mg/kg, and 3675.24 ± 794.68 mg/kg, respectively. However, Cd was more abundant in the gizzard and gut, as its hydrophilic nature meant Cd was mainly ingested orally, and the C max of Cd in E. fetida , P. guillelmi, and M. guillelmi in the gizzard and gut, respectively, was 452.43 ± 48.33 and 360.83 ± 44.36 mg/kg, 996.03 and 809.11 mg/kg, and 93.37 and 109.19 mg/kg. By contrast, for E. fetida , more Cd was distributed in the body wall (average 50.16%), possibly due to its high affinity for this organ (the average logK L for the body wall was −3.60) predicted by the Langmuir adsorption model, also the worm ingested less soil. These data suggest that ecotype influences the accumulation and distribution of pollutants in earthworms, as their ecophysiological properties (e.g., motility, food choices, and feeding efficiency) affect their exposure to and ingestion of pollutants. The distinct chemical properties of BaP and Cd also appear to affect their accumulation and distribution in earthworms. These factors should be considered when using earthworms as bioindicators in environmental risk assessments. [ABSTRACT FROM AUTHOR]

Different pollutants induce distinct toxic responses in earthworms ( Eisenia fetida ). Here, we used proteomics techniques to compare the responses of E. fetida to exposure to the 10% lethal concentration (14d-LC 10 ) of benzo[ a ]pyrene (BaP) or cadmium (Cd) in natural red soil (China). BaP exposure markedly induced the expression of oxidation-reduction proteins, whereas Cd exposure mainly induced the expression of proteins involved in transcription- and translation-related processes. Furthermore, calmodulin-binding proteins were differentially expressed upon exposure to different pollutants. The calcium (Ca 2 + )-binding cytoskeletal element myosin was down-regulated upon BaP treatment, whereas the Ca 2 + -binding cytoskeletal element tropomyosin-1 was up-regulated upon Cd treatment. Some proteins exhibited opposite responses to the two pollutants. For instance, catalase (CAT) and heat shock protein 70 were up-regulated upon BaP treatment and down-regulated upon Cd treatment. A significant ( p < 0.05, one-way ANOVA with least-significant difference (LSD) test) increase in the level of reactive oxygen species (ROS) and CAT activity further showed that BaP mainly induces oxidative stress. Real-time PCR analysis showed that mRNA expression often did not correlate well with protein expression in earthworms subjected to Cd or BaP treatment. In addition, the expression of the gene encoding the protein metallothionein, which was not detected in the protein analysis, was induced upon Cd treatment, but slightly reduced upon BaP treatment. Therefore, BaP and Cd have distinct effects on the protein profile of E. Fetida with BaP markedly inducing ROS activity, and Cd mainly triggering genotoxicity. Capsule summary Distinct patterns of protein expression are induced in earthworms upon exposure to different pollutants; BaP markedly induces high levels of ROS, while Cd resultes in genotoxicity. [ABSTRACT FROM AUTHOR]

The aims of the present study were to compare the toxic effects of benzo[ a]pyrene (B aP) and to screen for rapid and sensitive biomarkers that can be used to assess the environmental risks of B aP in earthworms in different natural soil types. The authors exposed Eisenia fetida to 2 types of soil (red soil and fluvo-aquic soil) spiked with different concentrations (0 mg kg−1, 1 mg kg−1, 10 mg kg−1, 100 mg kg−1, and 500 mg kg−1) of B aP for 7 d or 14 d. Benzo[ a]pyrene-induced weight variation altered the activities of antioxidant enzymes (superoxide dismutase [SOD]; catalase [CAT]; and guaiacol peroxidase [POD]) and changed the content of malondialdehyde (MDA). In addition, using the comet assay, the authors determined the DNA damage in earthworms. The results revealed that the comet assay was suitable for evaluating the genotoxicity of B aP in the soil, even at the lowest examined concentration. The MDA content was the least sensitive indicator of B aP toxicity. A 3-way analysis of variance (ANOVA) was used to determine whether the soil type, exposure concentration, and duration affected the B aP toxicity. The antioxidant enzyme activities and the MDA content were shown to be significantly correlated with the exposure concentration. The percentage of weight variation ( p < 0.001), CAT activity ( p < 0.05), and SOD activity ( p < 0.01) were significantly affected by the soil type, and the POD activity ( p < 0.01), CAT activity ( p < 0.001), and SOD activity ( p < 0.001) were significantly affected by the exposure duration. Therefore, measuring DNA damage in earthworms is a simple and efficient means of assessing B aP genotoxicity in a terrestrial environment, and the effects of the soil type and exposure time on the other parameters that were investigated in E. fetida, which were used as responsive biomarkers, should be considered. Environ Toxicol Chem 2014;9999:1-8. © 2014 SETAC [ABSTRACT FROM AUTHOR]

Abstract: The effect of earthworms on soil hydrolases (protease, urease, invertase, and alkaline phosphatase) and dehydrogenase activities was investigated in maize residue amended rice–wheat rotation agro-ecosystem. Experimental plots in the rotation had five treatments, i.e. incorporation or mulching of maize residues with or without added earthworms and an untreated control. The application of maize residues to soil without earthworms significantly enhanced the five soil enzyme activities compared with the control treatment during rice and wheat cultivation. The presence of earthworms further significantly enhanced protease activity in the soils with both incorporated and mulched maize residues during two cultivation seasons, but only significantly increased alkaline phosphatase activity in the soil with incorporated maize residue during the rice cultivation season. Invertase activity was significantly enhanced by the presence of earthworms in the soil with maize residue incorporation during two cultivation seasons. There were no changes in dehydrogenase activity when earthworms were present. Additionally, the five enzyme activities in earthworm casts were significant higher than those in the surrounding soil, especially dehydrogenase and invertase activities. Whatever the treatment, the values obtained for the enzyme activities in both soil and casts, except for dehydrogenase activity in earthworm casts, were significantly higher under wheat than those in rice-cultivated soil. These results indicate that the presence of earthworms strongly affected soil enzyme activities, depending on the method of organic residue application, and the enhanced enzyme activities of earthworm casts probably contributed to the surrounding soil enzyme activities. [Copyright &y& Elsevier]

Abstract: The influence of earthworms on nematodes and protozoan communities was determined during the wheat phase of a six year rice–wheat rotation agro-ecosystem. Experimental plots in the rotation had five treatments, i.e. incorporation or mulching of maize residues with or without added earthworms and a control. The addition of maize residues to soil strongly affected the abundance and community structure of nematodes and protozoa in the absence of earthworms. The presence of earthworms gave significantly lower total nematode numbers at all soil depths following maize residue incorporation than the same treatment without earthworms, and also gave lower (although not significantly) total nematode numbers in the upper soil layer following maize residue mulching than the same treatment without earthworms. This was mainly due to a significant decrease in bacterial-feeding nematode numbers. Earthworms also strongly affected the distribution of the number of total nematodes and two trophic groups (bacterial and plant feeders) with soil depth. In the presence of earthworms, total protozoan and flagellate numbers significantly increased at all soil depths following both incorporation and mulching of maize residues, while numbers of amoebae increased only when maize residues were mulched. Additionally, in earthworm casts total nematode numbers (mainly bacterial and fungal feeders) were significantly higher, whereas total protozoa numbers (mainly flagellates and amoebae) were significantly lower than that in soil from 0 to 5cm layer. These results indicated that earthworm activity could affect the abundance and community structure of microfauna, and change their distribution between soil layers and cast material, depending on the mode of application of organic residues. [Copyright &y& Elsevier]

A correction is presented to the article on "Does ecotype matter? The influence of ecophysiology on benzo pyrene and cadmium accumulation and distribution in earthworms" which to be appeared on 2018 issue.