ChapterPDF Available

Enchytraeids

Authors:
  • IFAB Institut für Angewandte Bodenbiologie, Hamburg, Germany

Abstract

Like most other soil organisms and especially soil fauna, potworms have been ignored for a long time, in both natural and agricultural systems, because they were simply deemed unimportant. One of the first occasions when enchytraeids attracted scientific attention was when they were suspected to be potential pest organisms. However, ecological research on potworms was also hampered by some practical problems: difficulties with their extraction from soil, and especially a lack of unambiguous taxonomic identification criteria. Since the development of relatively simple and reliable extraction methods and a revision of enchytraeid taxonomy, an increasing number of ecological studies have been carried out, and it has repeatedly been demonstrated that enchytraeids may constitute a major element of the soil faunal community in a variety of habitats.
G. Benckiser (ed.), Fauna in Soil Ecosystems: Recycling Processes, Nutrient Fluxes, and
Agricultural Production. Marcel Dekker, Inc., New York 1997
... They are rarely differentiated into taxonomic groups due to the relative complexity of identification [5]. Therefore, only few studies on the identification and analysis of their functional composition are available [6], although differences in ecological specialization of representatives of different genera of the family can be significant [5,7,8]. ...
... The total number of enchytraeids was calculated for each sample. They were identified to the genus or, when possible, species level and divided into ecological groups based on their preference for certain soil pH: basophilous, neutrophilous, and acidophilous [5][6][7][8][23][24][25]. Species with unknown pH preference and individuals not identified to the species level made RUSSIAN up an additional group that was not included in analysis. ...
... Table 1. Abundance (ind./m 2 ) of enchytraeid genera (bold) and species (where applicable) in different types of habitats in three study regions (the numbers of habitat replicates are shown in parentheses) and the division of enchytraeid taxa into ecological groups with respect to soil acidity and moisture preferences (according to[5][6][7][8][23][24][25]) ...
Article
Communities of soil animals (meso-and macrofauna) in rice paddies tend to be fragmented, and have extremely low abundance. Nevertheless, some groups, such as enchytraeids, may become dominant in flooded conditions, as shown in tropical rice agroecosystems. However, the fauna and functional composition of enchytraeids (Annelida, Clitellata, Enchytraeidae) under such conditions have not yet been studied at temperate latitudes. We have investigated enchytraeid communities and the ratio of their functional groups in the main rice-growing regions of Russia: Krasnodar krai, Primorsky krai, and the Republic of Kalmykia. Samples were taken in summer-early autumn of 2016 in four habitat types: flooded rice paddies, drained paddies occupied by upland crops, adjacent bunds, and undisturbed grasslands (control). Generalized linear model analysis showed that the factor habitat type and its interaction with the factor region had a significant effect on the total enchytraeid abundance, with the factor region alone having no such effect. Their abundance was the highest in the control habitats and bunds (mean and standard error for all the regions: 3278 ± 1131 and 3255 ± 762 ind./m 2 , respectively), being insignificantly lower in the paddies under upland crops (1282 ± 850 ind./m 2) and decreasing to a minimum of 415 ± 323 ind./m 2 in the flooded paddies. A comparison between the last two habitat types shows that enchytraeids can relatively quickly restore their abundance in the rice paddies after draining. Principal component analysis revealed a positive correlation between the density of enchytraeids belonging to basophilous ecological group and bioavailable phosphorus content. The correlation between the abundance of acidophilous enchytraeids and this parameter was negative. Thus, the abundance ratio of enchytraeid ecological groups could be used as an informative indicator of the concentrations of nutrient elements and depends on physical and chemical characteristics of paddy soils. Despite the low abundance of enchytraeids in these soils, they can be an important component of the detrital food webs during periods of paddy-drainage in intensive rice agroecosystems at temperate latitudes.
... Wolters, 1988;Williams and Griffiths, 1989;Briones et al., 1998;Cole et al., 2001Cole et al., , 2002van Vliet et al., 2004;Fox et al., 2006;Carrera et al., 2011). Up to 30% of the total organic carbon flow in a detrital food web may pass through the enchytraeid-controlled channels (as reviewed by Didden et al., 1997), but such rates are unlikely to be achieved for recalcitrant organic matter. However, the direct contribution of enchytraeids to rice crop residue degradation and carbon loss from soil, to our knowledge, has not yet been quantified. ...
Article
https://authors.elsevier.com/c/1YS4i8g13JWo3 (free access until March 15, 2019) The contribution of soil enchytraeids (potworms) to carbon cycling is often considered marginal and is therefore rarely quantified. In our experiment we aimed at evaluating the impact of the model enchytraeid species Enchytraeus buchholzi Vejdovsky, 1879 on rice straw degradation and associated CO2 release from soil. We filled 48 microcosms with soil collected in rice paddies of the Republic of Kalmykia, Russia, at 75% water holding capacity and added 0.5 g dry rice straw sealed in litterbags to each of them. Half of the microcosms were inoculated with 100 potworms. On days 3, 6, 9, 14, 21 and 31 after the start of the experiment, we measured CO2 emissions from soil. In addition, we terminated four microcosms with and four without enchytraeids at each of these dates to measure both rice straw mass loss and enchytraeid recovery rates. E. buchholzi significantly accelerated the relative rice straw mass loss (10.2 ± 1.4 and 14.2 ± 2.0%, respectively). It also significantly reduced CO2 emissions by 35% on average across the whole observation period. Though the number of potworms extracted dropped by 61% of the initial density up to day 9, it then consistently increased and reached a mean density of 365 individuals per microcosm at the end of the experiment. Considering both the rapid reproduction of E. buchholzi and the efficient mitigation of CO2 release, the promotion of enchytraeid activity may be a promising management measure for stabilizing carbon in paddy soils amended with rice straw. This opens up innovative perspectives for further research on exploiting the potential of the soil fauna for sustainable recycling of rice crop residues.
... It is the result of a lack of knowledge about the biology of enchytraeids and their superficial morphological similarity to the herbivorous nematodes. To date, no enchytraeid species is known to feed on the living tissue of healthy plants (Esser and Simpson, 1994;Didden et al., 1997;Schmelz et al., 2013). However, there are several papers of early naturalists in which they erroneous stated that potworms can be plant pests. ...
... enchytraeid numbers are usually associated to competition with earthworms (Räty, 2004 Räty andHuhta, 2003). However, Didden et al. (1997) found that both groups can perfectly coexist in the same soil depending on temperature and moisture levels and concluded that they occupy different niches. Therefore, by exhibiting better adaptations to specific conditions, certain species can exploit certain habitats more successfully than others. ...
Article
Full-text available
Litter biodegradation is a process of life. Organisms feed, reproduce, die and decompose. Decomposition is essential, and it is never complete. In addition, the elements generated by this process become new bricks for building more complex structures in a dynamically evolving environment. In this article, we show some pictures of the main actors in litter biodegradation. We also try to associate living organisms to the soil aggregates they generate, furnishing photographs of organisms and aggregates visible in the field even with a naked eye. The transformation of dead bodies, organs or cells and droppings in the soil ecosystem is influenced by biotic and abiotic factors and hence it must be considered as a dynamic, never ending, local evolution. Instead of focusing on specific data, we have tried to present the involved phenomena to a non-specialised public (naturalists, students, teachers, etc.) through the use of graphical schemes, indicating arrows, photographs, and drawings. In the end, readers will be aware that things are not as simple as expected, that static models cannot give a precise image of a reality in constant evolution. The article can be inspected as a photo album, read as a comic strip or used as a dictionary. The authors aim to illustrate rather than to explain the relationships between humus systems, climate and biodiversity.
... It is the result of a lack of knowledge about the biology of enchytraeids and their superficial morphological similarity to the herbivorous nematodes. To date, no enchytraeid species is known to feed on the living tissue of healthy plants (Esser and Simpson, 1994;Didden et al., 1997;Schmelz et al., 2013). However, there are several papers of early naturalists in which they erroneous stated that potworms can be plant pests. ...
Article
The authors evaluated the diversity of Enchytraeids in the no-tillage system cultivated with soybean over two years, the most used soil management technique for grain cultivation in Brazil. Samples were collected according to ISO 23611-3 and extracted with the hot-wet methodology. Compared to native forests, no-tillage areas presented less richness of genera, individual density, and changes to the structure of the community. Among the chemical and physical variables of the soil, it was identified that the clay, calcium, potassium, moisture and total nitrogen contents of the soil affect the enchytraeid community.
Article
Full-text available
Smaller body-sized invertebrate groups are known to be highly sensitive to environmental pollution. Like soil nematodes, enchytraeids have very permeable cuticles and come into direct contact with heavy metals; therefore they can be adversely affected by soil pollution. However, in contrast to nematodes, fewer data on enchytraeids are at our disposal to assess their functional responses to heavy metals. Such an assessment would be of greatest value, as in any edaphic community, enchytraeids are the only functional group bridging the detrital energy flux across the bacterial-driven and the fungal-driven pathways. For this purpose we investigated and evaluated the effect of heavy metals on the occurrence and biomass of enchytraeids in different soils in The Netherlands. Samplings of topsoils were carried out in 297 sites with Pleistocene sandy soils, river clay and sea clay under different environmental stress and all recovered enchytraeid species have been included in three existing phy-logenetical clades (hereafter: A, B, and C). Our results show that the biomass of the enchytraeid species belonging to the Clade C is highly correlated with Cr, Cu and Zn in sandy soils (all 2-tails significance values share p < 0.005, n = 186) but is correlated with Cu and Hg in loamy soils (p < 0.05, n = 111), whilst the biomass of the enchytraeid species belonging to the Clade B is highly correlated with either Cd + Cu + Pb in sandy soils (p < 0.025, n = 186) or Hg + Pb in loamy soils (p < 0.05, n = 111). The entire enchytraeid community actively contributes to promote the rapid turnover of soil organic matter. Given that clay-rich soils retain a much higher amount of heavy metals in contrast to sandy soils, most enchytraeids share different values as bioindicators according to the soil type, even comparing river clay with sea clay. Hence, elemental availabilities have disproportionately strong effects on enchytraeids and on the entire edaphic community according to the soil types.
Article
Full-text available
Enchytraeidae (Oligochaeta, Annelida) are often considered to be typical forestliving organisms, but they are regularly found in agroecosystems of the temperate regions of the world. Although less known than their larger relatives, the earthworms, these saprophagous organisms play similar roles in agricultural soils (but at a smaller scale), e.g., influencing soil structure and organic matter dynamics via microbial communities, and having a central place in soil food webs. Their diversity is rarely studied or often underestimated due to difficulties in distinguishing the species. New genetic techniques reveal that even in anthropogenically highly influenced soils, more than 10 species per site can be found. Because of their close contact with the soil pore water, a high ingestion rate and a thin cuticle, they often react very sensitively to a broad range of pesticides. Firstly we provide a short overview of the diversity and abundance of enchytraeid communities in agroecosystems. Afterwards, we explore the available data on enchytraeid sensitivity toward pesticides at different levels of biological organization, focusing on pesticides used in (mainly) European agroecosystems. Starting with non-standardized studies on the effects of pesticides on the sub-individual level, we compile the results of standard laboratory tests performed following OECD and ISO guidelines as well as those of higher-tier studies (i.e., semi-field and field tests). The number of comparable test data is still limited, because tests with enchytraeids are not a regulatory requirement in the European Union. While focusing on the effects of pesticides, attention is also given to their interactions with environmental stressors (e.g., climate change). In conclusion, we recommend to increase the use of enchytraeids in pesticide risk assessment because of their diversity and functional importance as well as their increasingly simplified use in (mostly standardized) tests at all levels of biological organization.
Article
Lumbricids and enchytraeids are two keystone fauna groups strongly responsible for the functioning of detrital food webs in temperate soils but acting at contrasting spatial scales. The relationships between both groups are poorly understood: considering their close kinship and trophic habits as generally microbi-/saprovores, competitive interactions are expected. However, due to engineering activities, various non-trophic earthworm impacts on enchytraeids also play a role, which has never been evaluated. We experimentally simulated and quantitatively estimated the effects of major non-trophic earthworm activities (burrowing, cast deposition, mucus release) and, in addition, of earthworm mortmass decay on the abundance of enchytraeids. Effects of two earthworm species belonging to epigeic (Lumbricus rubellus) and endogeic (Aporrectodea caliginosa) ecological groups were tested.
Article
Full-text available
Enchytraeids are a significant part of soil biota especially in arable land; it is therefore important to know their sensitivity to management. Reduced tillage (RT) is a cultivation method that benefits many groups of soil fauna, but the effects RT has on enchytraeids remains unclear. The aim of this study was to ascertain how the enchytraeid abundance at a research site on sandy soil in Northeast Brandenburg was affected by RT and conventional tillage (CT) during a ten year observation period and what reasons there may be for any observed effects of cultivation methods on enchytraeids. Works of several authors led to our hypothesis that a change in food availability and possible antagonistic relations to earthworms are likely to be the reasons for a negative effect of RT on enchytraeids abundance. Therefore, we examined the correlation between enchytraeids and plant residue as well as earthworms using Spearman's rank correlation coefficient. Our study showed that RT had a distinctly negative effect on the abundance of enchytraeids at our research site. The results of the study also showed that their abundance correlated significantly positive with plant residue under CT while under RT no correlation was ascertained. These findings support the thesis of Hendrix et al. (1986), which states that the bacteria-based food webs developing under CT favor organisms with high metabolic activity like enchytraeids, whilst the fungi-based food webs that occur under RT favor other soil animals such as earthworms. While earthworms were indeed favoured by reduced tillage at the experimental site, no clear relationship, neither positive nor negative, was found with respect to enchytraeid vs. earthworm abundances.
Article
Full-text available
Enchytraeus crypticus n.sp. and Enchytraeus doerjesi n.sp. were discovered in laboratory cultures of terrestrial enchytraeids in the course of a project evaluating various non-light-microscopical techniques for their taxonomic utility. Ultrastructural and molecular features of the two species are published elsewhere; the present paper describes their conventional morphological characters and their life cycle data under laboratory conditions.
Article
Full-text available
(1) Annual carbon and nitrogen budgets were calculated for four cropping systems: barley without N fertilizer (B0), barley fertilized with 120 kg N ha-1 year-1 (B120), a meadow fescue ley with 200 kg N ha-1 year-1 (GL), and a lucerne ley (LL) capable of fixing nitrogen. The data base included studies of above- and below-ground primary production and N uptake, decomposition, soil respiration, nitrogen fixation, gaseous N losses, N leaching, soil micro-organisms and soil fauna. All major inputs and outputs of C and N were determined from independent measurements, over a 2-year period. (2) Net annual primary production (including rhizodeposition) was 260, 480, 740 and 790 g C m-2 in B0, B120, GL and LL, respectively. Annual inputs of organic carbon to the soil were less different between crops, i.e. 150-180 g C m-2 in barley and 260-270 g C m-2 in the leys. Total annual soil respiration, 230 g C m-2 in barley and 350-400 g C m-2 in the leys, closely matched the input of C to decomposer organisms plus C respired by roots. Both leys accumulated C, mainly as increases in plant standing crop. (3) Total inputs and outputs of nitrogen were roughly balanced in the fertilized barley, while total N in the unfertilized barley declined by 4 g m-2 year-1. Total N increased in the nitrogen-fixing lucerne ley, with a net increase in plant standing crop of 9 g N m-2 year-1 and in soil N of 3 g N m-2 year-1. In contrast, the grass ley showed a net change in total N of -5 g m-2 year-1. (4) Net nitrogen mineralization ranged between 8 g m-2 year-1 in B0 and 21 g m-2 year-1 in GL, and corresponded to c. 1% of total soil N in barley and c. 2% of total soil N in the leys. The nitrogen balances and other data from the field experiment suggest that the grass ley considerably enhanced net mineralization of soil organic matter N. (5) Total losses of nitrogen due to leaching and gaseous emissions (denitrification, ammonia volatilization and NOx emission) ranged between 1 g N m-2 year-1 in B0 and GL to 2 g m-2 year-1 in LL. Denitrification rates were lowest in barley, but both unfertilized and fertilized barley leached more N than the leys. (6) There were no large differences in microbial biomass between treatments but estimated microbial production was 50% higher in the leys than in the barley treatments. This pattern corresponded to that of soil meso- and macrofauna biomass and total faunal consumption and respiration, where B0 < B120 < GL < LL.
Article
Ecological studies on soil nematodes, enchytraeids, collembolans and mites in a 1948 Pseudotsuga menziesii plantation at Shawnigan, British Columbia were made from March 1971 to March 1972. The plantation was thinned to 1,900 stems/ha and urea was applied at 0, 224 and 448 kg N/ha just before faunal sampling. Monthly samples were extracted in high-gradient apparatus, Murphy split funnels and simple wet funnels. Fifty-two and 53% of collembolans and mites, respectively, occurred in the top 5.3 cm of the 17.5-cm soil profile studied. The Pearson and Hartley power function test indicated that for intramonth sampling to show statistical significance of treatment, at least 10 samples per treatment would be required for any of the groups under experimental conditions similar to the one reported here. Collembolans and mites exhibited significant downward seasonal distribution, and urea treatment accentuated this phenomenon for all four groups, suggesting that sampling below 6 cm would be required to observe the full impact of urea fertilization on the soil fauna. Except for enchytraeids, seasonal population fluctuation contrasted with the generally observed pattern in temperate regions of spring and fall peaks and showed increases through the spring, culminating in summer and autumn maxima. Urea fertilization increased annual mean population of nematodes by 1.41 and 2.51 times the control for 224 and 448 kg N/ha, respectively, and decreased enchytraeids by 0.52 and 0.28 times the control for the same two fertilizer rates; collembolans and mites were not significantly affected.
Article
Larvae of the scarabaeid beetle Pachnoda ephippiata were used to evaluate 5 respirometers potentially applicable to studies of the ecological energetics of terrestrial invertebrates. Over a 3‐h period the Gilson differential respirometer, a simple constant‐pressure device, an infrared gas analyser, and a gas chromatograph gave a similar relationship between oxygen uptake (or carbon dioxide output × RQ‐) and the ash‐free dry weight of the larvae. A diaferometer lacked the sensitivity to give satisfactory results. The effect of varying several environmental factors on the respiration rate of the larvae was tested. Changing the illumination regime from light to dark to light had no significant effect on the rate of oxygen uptake; shaking the flasks caused a significant decrease. In a 24‐h run with the Gilson respirometer a period of high respiratory activity falling to a slowly declining ‘steady’ state was particularly noticeable in the largest larvae. Their respiration rate fell more sharply when approximately 50% of the available oxygen had been removed. Adding soil to the flasks extended the period of high respiratory activity, which lasted until the partial pressure of oxygen reached 50–60% of the original. Larval respiration rate declined after respired air in the flask had been replaced, but later increased towards a level predictable from unflushed controls. The IRGA respirometer demonstrated that larval carbon dioxide output was lower in room air than in air scrubbed of carbon dioxide. None of the respirometers most often employed by energeticists studying terrestrial invertebrates was entirely satisfactory. An apparatus incorporating a thermal conductivity detector (i.e., a diaferometer or modified gas chromatograph apparatus) would approach the ‘ideal’. However, the energy expended in metabolism can be estimated from the results obtained with a closed‐vessel respirometer (as opposed to a constant‐flow device) by increasing the measured respiration rate by a factor of about × 2.5.
Article
Three soils developed in Late Weichselian loess in France were studied to document morphological features related to agricultural and faunal activities. One soil had been in deciduous forest at least 100 years, one had been in permanent grass pasture for at least 25 years, and one had been annually cultivated for at least 50 years. The investigation included field descriptions, chemical and physical characterizations, and thin section studies. The surface horizon (Ap) of the cultivated soil was thicker than surface horizons of the forest and pasture soils, probably because of deep tillage (to about 35 cm depth). Another probable effect of deep tillage of the cultivated soil was to mix horizons, destroying evidence of an eluvial zone near the soil surface. Soil in both forest and pasture exhibited numerous features related to faunal activity in both surface and subsurface horizons, including large channels, abundant fecal pellets, channel infillings, and organic intercalations. These features were correlated with rather weak expression of illuvial clay accumulations in pores of the B horizons, although bulk characterization indicated the presence of argillic horizons. In contrast, B horizons of the cultivated soil had somewhat lesser macroporosity and fewer fecal pellets, infillings, and intercalations but strongly expressed illuvial coatings. With the assumption that the three soils had similar morphologies before cultivation, the observations suggest that greater faunal activity in the soils in forest and pasture led to more significant disruption of illuvial pedological features than in the soil under cultivation.
Article
The influence of the enchytraeid species Cognettia sphagnetorum on N mineralization in homogenized mor humus was examined in a laboratory study. The mor humus was incubated in containers (150 ml) for 8 months at various temperatures and with different moisture levels. Two series were used, one with C. sphagnetorum and one without. The presence of enchytraeids in the cultures increased the level of NH4+ and NO3- by about 18% compared with the cultures without enchytraeids. Almost 40% of this difference was explained by the decomposition of dead enchytraeids. Temperature and soil moisture were the most important factors controlling the mineralization rate. The optimum moisture for N mineralization was between pF 1.6 and 1.1.
Article
Enchytraeids were sampled in 1980-85 in an agricultural field experiment with 4 cropping systems: barley Hordeum vulgare without nitrogen fertilization (BO); barley receiving 120 kg N ha-1yr-1 (B120); grass ley (GL); and lucerne Medicago sativa ley (LL). The enchytraeid fauna was composed of 3 widely distributed, sexually reproducing species of high reproductive capacity. Juveniles were mainly found in summer and early autumn. Mean enchytraeid abundance in September in 5 yr did not differ significantly between cropping systems but the dynamics did so. Mean abundance was 8400 m-2 in the top 20 cm of the soil and mean biomass was 0.45 g dry mass m-2. The vertical distributions of enchytraeid numbers and biomass in BO and B120 were more uniform than in GL, where the enchytraeids were concentrated at the surface. In LL, the vertical distribution was intermediate between those for GL and barley. The vertical distribution of enchytraeids reflected distribution of roots, and possibly organic matter and pore space. Towards the end of the experiment, abundance and biomass were greater in BO than in B120. In the 2 months after ploughing, enchytraeid abundance increased in GL from 4700 to 28 000 m-2 and dry biomass increased from 0.3 to 0.9 g m-2. Respiration of the total enchytraeid fauna was 1.2-2.6 g C m-2yr-1. This constituted 0.5-1.6% of total heterotrophic soil respiration. Consumption (16-34 g dry mass m-2yr-1) corresponded to 3-12% of organic matter input to the soil. -from Authors
Article
Enchytraeidae colonized faster than most microarthropods and had the highest biomass during the first summer. Arthropod species composition changed between the early phase (first autumn, spring and summer) and later phases of decomposition, and was possibly related to substrate changes. After the early phase arthropod species composition and diversity were similar between samplings. Collembola and astigmatid mites dominated in abundance, gamasid mites in biomass. Collembola had higher body masses in early samplings than in later samplings, indicating that adults colonized the litter-bags and then reproduced. Numbers of arthropods and enchytraeids per unit volume were higher in the straw than in the surrounding soil. Contributions to total carbon loss were small, 0.8% for enchytraeids and 0.2% for microarthropods.-from Authors