Predatory Nematodes Research Articles

Uptake of phytodetritus by meiobenthos using 13C labelled diatoms and Phaeocystis in two contrasting sediments from the North Sea

Meiobenthic uptake of 13C labelled diatom Skeletonema costatum and Prymnesiophyte Phaeocystis was investigated in permeable and fine grained depositional sediments from the Southern Bight of the North Sea at different sediment horizons. Both the diatom and Phaeocystis–derived organic matter (OM) cascaded into meiobenthic biomass in low but similar percentages and label uptake was highest at the upper cm in both stations. Phaeocystis–derived OM might be as important as diatoms as a food source for the meiobenthos. Meiobenthic biomass in the coarse sediment was lower than in the fine sediment; however label uptake per unit of organism carbon was higher. This was explained as an adaptation to an environment where only low amounts of labile OM are present. In this station, the so-called “stout nematodes” (length to width ratio < 15, [Vanaverbeke, J., Soetaert, K., Vincx, M. 2004a. Changes in morphometric characteristics of nematode communities during a spring phytoplankton bloom deposition. Mar. Ecol. Prog. Ser. 273, 139–146]) showed lower uptake compared to the slender nematodes. Therefore their previously reported opportunistic response to a pulsed food supply must rely then on their life-history characteristics. In finer sediments Sabatieria showed the highest uptake at the 1–3 cm layer, reflecting migration to the sediment-water interface to feed on freshly deposited labile OM. Richtersia 13C uptake was fairly low, indicating the exploitation of another carbon source than the one derived from Skeletonema costatum or Phaeocystis. Enoploides presented the highest uptake, indicating that these predacious nematodes have another food source besides meiobenthic preys. Generally total uptake was low and not nearly sufficient to meet nematode carbon requirements.

IN VITRO MASS PRODUCTION OF PASTEURIA PENETRANS (MANKAU) SAYRE AND STARR FOR THE MANAGEMENT OF MELOIDOGYNE INCOGNITA (KOFOID AND WHITE) CHITWOOD

ABSTRACT Plant parasitic nematodes are parasitized and preyed by a variety of soil organisms which includes predatory nematodes, fungi, bacteria, viruses, protozoans, turbellarians, tardigrades, mites and other microarthropods. One such spore forming and an obligate parasite is Pasteuria penetrans. The major limitation in the use of Pasteuriaspp. is their inability to grow in the absence of host nematodes. In vivo systems although proven are unlikely to be adopted for large scale application in most farming systems. Attempts were made to culture the organism in in vitro. Among the symbiotic bacteria used for mass production co-culturing with Enterobacter proved to be successful in culturing this obligate organism in a specially developed medium for mass multiplication.

Suppression of root-knot nematodes in natural and agricultural soils

The potential of the invertebrate communities in agricultural and natural soils to suppress Meloidogyne incognita on coleus ( Coleus blumei) was evaluated in two greenhouse experiments. Soil from adjacent natural and agricultural habitats was collected from four locations that had very different soil types (loamy sand, muck, sand and rock). Soil of each type was placed into pots, planted with coleus seedlings, inoculated with 2000 eggs of M. incognita, and arranged in a 4 × 2 factorial design. Root-knot nematodes were suppressed in natural soil compared to agricultural soil for loamy sand, sand and rock soils, but not for muck soil. Plants grew larger and had less root galling in natural soils than in agricultural soils. Free-living nematodes (bacterivores, fungivores, omnivores and predators) were monitored but did not show population patterns consistent with the suppression of root-knot nematodes observed in natural soils. Reasons for the opposite result (higher root-knot levels in natural than in agricultural soil) on muck soil are unknown, but this soil type was very different from the other soils in its unusually high organic matter content and very low levels of omnivorous and predatory nematodes. The agricultural muck in particular was unusually low in fungivorous nematodes and extremely high in levels of sodium and macronutrients. Despite the exception on the muck soil, the relative suppression of root-knot nematodes in natural compared to agricultural soils of the other three soil types (loamy sand, sand and rock) support the idea that potential for nematode suppression may be greater in natural than in agricultural soils.

Dynamics of sustainable grazing fauna and effect on performance of gas biofilter

The inherent operational problems of biofilters such as a pressure drop increase and nutrient limitations were managed in a toluene-removing gas biofilter with a sustainable grazing fauna consisting of micrometazoa and ciliate protozoa. Dynamic populations of predatory nematodes (Caenorhabditis sp.), rotifers (Philodina sp.), tardigrades (Echiniscus sp.) and fly larvae represented the micrometazoa community in the filter bed. Colpoda inflata, Euplotes harpa and Acineria sp. constituted the grazing ciliate community. The spatiotemporal distribution and abundance of the grazing fauna depends on physicochemical conditions and interspecies interactions in the biofilter. Of the micro metazoa, Caenorhabditis and Philodina tolerated wide concentration ranges for toluene (0.75-2.63 g m(-3)) and CO(2) (0.92-6.08 g m(-3)) and maintained stable populations of 3.4-4.7 x 10(3) and 5.8-7.65 x 10(4) g medium(-1), respectively. The grazing fauna supported a stable toluene-degrading bacterial community composed of four Pseudomonas spp. Under a maximum toluene load of 120.72 g m(-3) h(-1), at steady-state conditions 80% toluene removal was achieved in the biofilter. Of the grazing organisms, owing to their reproductive cycle and feeding behaviour, fly larvae were not suited for application in the biofilter. Meanwhile, organisms such as nematodes, rotifers and ciliates capable of tolerating a wide pollutant concentration range and maintaining a sustainable population are ideal candidates for application in biofilter technology.

First field release of a predatory nematode, Mononchoides gaugleri (Nematoda: Diplogastrida), to control plant-parasitic nematodes

Predatory nematodes are an important entity of the soil food web with biological control potential against plantparasitic nematodes (Bilgrami, 1997). Low fecundity, long life cycle, difficult culture conditions, cannibalism and susceptibility to changing environmental conditions restrict the use of mononchs and stylet-bearing predators as biological control agents. The possibility of using nematodes as biological control agents of plant-parasitic nematodes lies with diplogastrid predators (Diplogastrida). Among the advantages of diplogastrids over mononchs and stylet-bearing predators, Siddiqi et al. (2004) and Bilgrami et al. (2005) have listed ease of in vitro culture, high rates of reproduction and predation, short life cycle, and ability to detect and respond to prey attractants and rare cannibalism. Diplogastrids possess greater tolerance to unfavourable environmental conditions (Bilgrami, 1997), density-dependent predation (Bilgrami et al., 2005), ability to reduce root galling (Fauzia et al., 1998) and decrease in parasitic nematode populations in pots (Osman, 1988). This is the first report of a predatory nematode being field-released to control plant-parasitic nematodes. Our goal was to evaluate the effects of Mononchoides gaugleri (Nematoda: Diplogastrida) on naturally occurring plantparasitic and non-parasitic nematode populations in a turfgrass field. A field experiment was conducted at Rutgers University Turfgrass Station, New Brunswick, NJ, USA. The experiment was laid out in a completely randomised design within a 260 × 170 cm plot. Forty 10 cm long sections of PVC pipe (10 cm internal diam.) were driven into the ground in five vertical rows; each row was 20 cm apart and contained eight PVC pipes. The area encircled by the pipe is referred to as a microplot. Thirty-nine microplots were divided into three groups, i.e., controls I and II, and

Laboratory studies on the biocontrol potential of the predatory nematode Koerneria sudhausi (Nematoda: Diplogastridae)

Abstract The predatory nematode Koerneria sudhausi reproduced on bacteria that developed spontaneously on a nutrient medium in Petri dishes. The nematode population had a female/male ratio of 2.9 : 1, but female nematodes could reproduce asexually on the bacteria. Each female produced about 60 progeny at 25°C in 9 days without mating. The generation time (egg to egg) at the same temperature was 8 days. Koerneria sudhausi reproduced at 17°C at the same rate as at 25°C, if the bacteria were available as a food source. When the nematode was introduced to a monoxenic culture of Meloidogyne javanica on tomato roots on agar, the nematode fed on second-stage juveniles and eggs. The nematodes introduced to M. javanica-inoculated soil before transplanting tomato seedlings reduced the root galling index in pot experiments. The results suggested that this predatory nematode, K. sudhausi, may serve as a candidate for a biological control agent against root-knot nematodes, because the nematode can be easily cultured on bacteria and achieve a high reproduction rate.

Predator-prey relationship between the cyclopoid copepod Diacyclops bicuspidatus and a free-living bacterivorous nematode

Abstract The potential of copepods as predators of free-living nematodes was tested by presenting Diacyclops bicuspidatus, a common holarctic cyclopoid copepod, with Panagrolaimus sp. as prey in the laboratory. Diacyclops bicuspidatus readily fed on nematodes of all size classes, including prey longer than itself. No size preference was observed. Handling times varied between a few seconds and several minutes, depending on the size of the prey. At different prey densities, the feeding rates of D. bicuspidatus followed a type II functional response. Starved D. bicuspidatus consumed up to 45.1 nematodes in 2 h, equivalent to 43.5% of the copepod's body mass. Indications that nematophagous nutrition is common among freshwater copepods are discussed.

Cover crops and organic mulches for nematode, weed and plant health management

AbstractTraditional cover cropping systems for nematode management seldom consider weed and soil nutrient management concurrently. Integrating cover crops suppressive to plant-parasitic nematodes with a cover crop mulching system could improve traditional approaches. Two field experiments were conducted in 2003 and 2004 to evaluate 'Tropic Sun' sunn hemp (Crotalaria juncea) and 'Iron Clay' cowpea (Vigna unguiculata) as summer cover crops and as organic mulches. Both experiments were in a 3 × 3 split-plot design in which the main plots were summer planting of sunn hemp, cowpea or fallow, and the subplots were organic mulch of sunn hemp, cowpea or no mulch. The summer cover crop was followed by turnip (Brassica rapa) and lima bean (Phaseolus lunatus) in the autumn. Using sunn hemp as organic mulch suppressed root-knot nematodes more effectively than using it as a cover crop, but only on a less susceptible host such as turnip, and not on a very susceptible host such as lima bean. While sunn hemp as a cover crop failed to enhance beneficial free-living nematodes, sunn hemp as an organic mulch enhanced bacterial-feeding nematode population densities. Sunn hemp mulch also suppressed broadleaf weeds but not grasses or nutsedges. Although sunn hemp and cowpea cover crops did not increase lima bean N and K content, their mulches increased N and K content. Similar results were observed for turnip and lima bean yields. Population density of root-knot nematodes was positively related to abundance of omnivorous nematode in 2003. The abundance of plant-parasitic nematodes was negatively related to the infestation levels of Pasteuria penetrans, and the abundance of predatory nematodes in 2004. Factors that might have affected the performance of sunn hemp on nematode communities are discussed.

Actus salvadoricus Baqri and Jairajpuri (Mononchida: Mylonchulidae) from Japan with comment on the phylogenetic position of the genus Actus based on 18S rDNA sequences

The nematode genus Actus belonging to the order Mononchida, an important group of predatory nematodes, is rare in the world. Actus salvadoricus Baqri and Jairajpuri, 1974, which had been described from El Salvador, were found from subtropical forest in the northern part of Okinawa Island, Japan. Its morphological observation is made herein and its phylogenetic position is elucidated based on 18S rDNA sequence. A. salvadoricus collected from Okinawa is characterized by having its buccal cavity with a moderately developed dorsal tooth, vertical subventral plates with a single row of denticles arranged as 3:3 or 3:4 or 2:4 on two plates, distinct excretory pore, elongate-conoid ventrally arcuate tail, with tandem caudal glands and terminal spinneret. Based on the nearly complete 18S rDNA sequence data already known and revealed in this work, phylogenetic trees of Mononchina were constructed using parsimony and maximum likelihood algorithms. The results show that the genus Actus forms a sister group with the species of the genus Mylonchulus in the suborder Mononchina, showing the valid status of its taxonomic group. Jpn. J. Nematol. 38 (2), 57-69 (2008).

Role of tardigrades in the suppressive service of a soil food web

In a previous study, soil suppressiveness to populations of the plant-parasitic nematode Meloidogyne incognita was correlated with abundance of omnivore and predatory nematodes. In the current study, performance of the regulatory function switched from nematodes to tardigrades when predatory nematodes disappeared due to predation pressure and/or unfavorable environmental conditions. Two tardigrade species, Macrobiotus richtersi and M. harmsworthi effectively suppressed nematode populations. While there were significant changes in the soil food web over time, the regulatory function was maintained. Under experimental conditions, M. richtersi consumed 61 nematodes per day, indicating that tardigrades may significantly reduce nematode biomass. The impact of tardigrades on soil food web dynamics and their relationships with nematodes are discussed.

Soil nematode community, organic matter, microbial biomass and nitrogen dynamics in field plots transitioning from conventional to organic management

Dynamics of soil bulk density, organic matter, microbial biomass, nitrogen, and nematode communities were assessed for a period of 4 years in field plots transitioning from conventional to organic farming practices. A rotation of soybeans, corn, oats and hay was used as an organic transitioning strategy and the conventional farming system had a corn and soybean rotation for comparison. Organic corn received raw straw pack beef manure and poultry compost at the rate of 27 and 28 Mg/h, respectively, and organic oats received raw straw pack beef manure and poultry compost at the rate of 18 and 1.8 Mg/h, respectively, while conventional plots received synthetic fertilizers. All crops in the organic system received primary tillage (chisel plow, disked and tined) whereas only corn received primary tillage in the conventional system but soybeans were no-till. Weed control was mechanical (twice diskings, rotary hoeings and row cultivation) in the organic system whereas herbicides were used in the conventional system. Soil bulk density did not differ in the two systems over a 4-year period but organic farming had slightly higher organic matter, mineral associated organic matter and particulate organic matter. Conventional system had more N in the mineral pools as indicated by higher NO 3 −-N whereas organic system had higher N in the microbial biomass indicating shifts in nitrogen pools between the two systems. Bacterivore nematodes were more abundant in the organic than the conventional system for most of the study period. In contrast, the conventional system had significantly higher populations of the root lesion nematode, Pratylenchus crenatus, than the organic system after completion of the rotation cycle (transition period) in spring 2004. The organic hay plots had the lowest populations of P. crenatus compared to corn, soybeans and oats. Nematode faunal profile estimates showed that the food webs were highly enriched and moderately to highly structured and the decomposition channels were bacterial in both systems. The lack of differences in structure index between the organic and conventional systems is probably due to the excessive tillage in the organic farming system, which may have prevented the build up of tillage-sensitive omnivorous and predatory nematodes that contribute to the structure index. We conclude that transition from conventional to organic farming can increase soil microbial biomass-N and populations of beneficial bacterivore nematodes while simultaneously reducing the populations of predominant plant-parasitic nematode, P. crenatus. Our findings also underscore the potential benefits of reducing tillage for the development of a more mature soil food web.

A new species of Trileptium (Nematoda, Thoracostomopsidae) from a sandy beach in southeastern Australia, with a key to species and observations on geographical distribution

Thoracostomopsidae are common predatory marine nematodes found in littoral and sub‐littoral sands. The buccal cavity is characterised by a mandibular complex and onchia (teeth) forming grasping jaws. Three constituent subfamilies and genera are distinguished by variations in the development of these structures. Of the three subfamilies, Thoracostominae have been found in sub‐littoral habitats and have not been reported from Australia. A number of species from several genera of Enoplolaiminae have previously been recorded from southeastern Australian beaches. In this paper, Trileptium australis n. sp. belonging to the third subfamily, Trileptiinae, is described from one of these beaches. In this genus, weakly developed mandibles and one, or three, well developed onchia are situated closer to the mouth opening than in Enoplolaiminae, and the lips have a lower profile. Important specific diagnostic characters of Trileptium australis n. sp. are the possession of three onchia, absence of cuticular annulation, presence of a pre‐cloacal supplementary organ, thin strongly curved spicules with mid‐ventral pegs and a gubernaculum that loops over the spicules. A dichotomous key for the 11 described species, based on male characters, is provided. The geographical distribution of all the described species is reviewed. One species, T. subterraneum has a very wide geographical distribution, but other species appear to be restricted to one sea or ocean.

Collembolans feeding on soil affect carbon and nitrogen mineralization by their influence on microbial and nematode activities

We manipulated Collembola Folsomia candida Willem density and observed the density effect on carbon and nitrogen mineralization and on nematodes in microcosms filled with mineral soil. Collembolan densities were 0 (control), 25 (low), 100 (medium), and 400 (high) individuals per microcosm. The Collembola enhanced soil respiration and nitrogen mineralization rate in a density-dependent manner (P < 0.05). The correlation between collembolan density and the metabolic quotient of microbes, qCO2, was weakly positive (r = 0.44, P < 0.05). Collembola did not affect microbial biomass. These results suggested that enhanced carbon and nitrogen mineralization was an indirect effect of Collembola mediated by increased microbial activity. Collembola changed the Cnema/Cmic ratio, but only when present at the low density. Thus, Collembola had both positive and negative effects on the nematode population. The positive impact probably depends on the enhancement of microbial activity due to Collembola grazing behavior, while the negative effect appears to result from predation of nematodes.

Changes in nematode communities at the long-term sand extraction site of the Kwintebank (Southern Bight of the North Sea)

We investigated the long-term effects of sand extraction activities on the nematode communities from the Kwintebank. Although changes in nematode community composition cannot be completely uncoupled from natural processes, we suggest that the morphological changes in the sandbank and physical disturbance associated with the dredging activities indeed affected nematode community composition. Nematode diversity did not change since the start of the extraction activities but nematode community composition changed significantly. The SIMPER routine identified predatory nematodes to be important for the within group similarity at the start of the exploitation, while similarity in 1997 and 2001 was determined by the contribution of deposit feeding nematodes. In addition, long nematodes, vulnerable to physical disturbance became less important. These changes are attributed to long term changes in sediment characteristics in combination with additional short-term disturbances by the creation and filling of dredge furrows which are related to the extraction activities.

Consumption rate of phytonematodes by Pergalumna sp. (Acari: Oribatida: Galumnidae) under laboratory conditions determined by a new method

Although several generalist species of Pergalumna are known to be nematode predators, the potential of oribatid mites as natural enemies of phytonematodes has been underestimated. The objective of this work was to estimate the consumption rate of a Pergalumna sp. when feeding on two major pest nematodes, Meloidogyne javanica and Pratylenchus coffeae, under laboratory conditions. A new method was used, in which live nematodes are offered to mites and subsequently consumption is quantified based on the sclerotized, well preserved structures in the mite's fecal pellets. The assay was evaluated during 5 days, at 25 degrees C and 96% relative humidity, with three replicates for each nematode species. Every replicate consisted of a group of four mites isolated in an arena, to which 400 nematodes were transferred daily. The daily produced fecal pellets were mounted in Hoyer's medium for examination under a microscope. The nematode buccal stylets and cephalic frameworks were counted to estimate the number of nematodes consumed. It was estimated that a single mite daily ingested 18.3 +/- 0.8 (mean +/- SE) M. javanica (J(2) juveniles) or 41.6 +/- 7.2 P. coffeae (juveniles + adults), the maximal daily consumption being 34 M. javanica and 73 P. coffeae. The method showed to be practical, precise and suitable for laboratory studies in which nematophagous mites classified as engulfers are included.

Effects of Kodiak® (Bacillus subtilis Strain GBO3) on Soil-Inhabiting Nematodes Near the Rhizosphere of Treated versus Untreated Snap Bean Seeds In Situ

ABSTRACT A field study was conducted at the West Virginia University Organic Research Farm to determine the effect of the bacterial biological control agent Kodiak® on beneficial soil nematodes. Kodiak® was applied to bean seeds prior to planting, and predatory, bacterial-feeding, and plant parasitic nematode abundance near the bean roots was monitored during two growing seasons. The abundance of non-target, beneficial soil nematodes within and around bean rhizospheres did not differ overall among plants treated with Kodiak® versus untreated plants. The data presented here do not indicate any detrimental or non-target impacts of Kodiak® on soil nematodes. Additionally, bean yield was not affected when the product was used in a manner consistent with organic farming practices.

The somatic female gonad of Cephalobidae (Nematoda): cellular architecture and associated function

Abstract The female reproductive system of the free-living nematode family Cephalobidae is examined by means of differential interference contrast, scanning electron and fluorescent microscopy. The model nematode Caenorhabditis elegans and the predatory nematode Prionchulus punctatus are also included in this study; the former mainly to test our results with the very detailed knowledge of this model organism, the latter to provide a representative of the more distantly related Enoplea. In this comparative approach, the analysed gonad structures are discussed with respect to their functional and phylogenetic significance. The general cellular composition of the cephalobid gonad – namely an oviduct comprising two rows of four cells, a distinctly offset spermatheca consisting of 8-16 cells, and a uterus composed of distinct cell rows – differs from all known Nematoda except that of the plant-parasitic Tylenchomorpha. Despite the striking evolutionary conservation of the cellular architecture of the cephalobid gonad there is a complex subcellular specialisation, namely a significant and functionally relevant variation in myofilament organisation, both among Cephalobidae and between major groups of nematodes. We demonstrate the presence of microfilaments that vary in pattern among species and that may play an important role in egg propulsion. The phenomenon of endotokia matricida, in which eggs do not leave the female body, is found to be associated with a massive rupture of the cytoskeleton in the uterus wall. The complexity of the myofibril structure and the associated potential to propagate oocytes actively cannot be solely explained by differences in phylogenetic history, but is also linked to body diameter. In the larger Acrobeloides maximus, the proximal end of the ovary sheath is adorned with 12 distinct longitudinal bands, antibody binding positively for paramyosin, while in the smaller Cephalobus cubaensis myofilament organisation is at random.

Effects of tillage and fertilizer on nematode communities in a Japanese soybean field

No-tillage (NT) cropping systems develop distinct soil ecosystems characterized by a diverse soil fauna and slow fungal decomposition. However, nematode community analyses sometimes fail to detect these characteristics because the treatment before study or the sampling period is too short or the studies are not comprehensive. Different nematode taxa may occur depending on the geographic region and soil type, thereby affecting the usefulness of nematode analyses for soil biological assessment. However, studies in Asia are scarce. Thus, in this 2-year study, we compared nematode populations, community structures, and soil physicochemical properties between long-term NT and conventional tillage (CT) treatments combined with chemical (CF), organic (OF), or no (NF) fertilizer treatments in a Japanese soybean field. We then examined whether nematode diversity and community indices could detect differences among the treatments in the Japanese andosols. Although the effects of tillage on nematode densities were significant, the overall trend in NT–CT differences was not clear, except for omnivores and Meloidogyne. The effects of tillage on nematode diversity and community indices were apparent: diversity indices, maturity index (MI) and related indices, structure index, and channel index were higher, whereas enrichment index (EI) was lower in NT because of higher densities of K-strategy taxa, fungal and facultative root feeders, and lower densities of r-strategy bacterial feeders. Fertilizer treatments also affected nematode densities: most feeding groups were less abundant in NF and predatory nematodes were more abundant in OF than in other treatments. OF increased nematode diversity via an increase in microbivorous and predaceous nematodes. However, the effects of fertilizer on most community indices were not apparent. Interactions between tillage and fertilizer effects were significant for Pratylenchus and total nematode densities, MI, and EI. Among the soil properties differing among treatments, Ca and Mg content, cation exchange capacity, and percent total nitrogen affected nematode community structure. In conclusion, nematode community analyses using index calculations are useful for assessing soil biological properties under different tillage treatments in Japanese andosols, as well as in soil types in other countries. However, index calculations were less sensitive at detecting fertilizer treatment effects, probably because of simultaneous increases in r- and K-strategy nematodes and OF compost that was too decomposed. Other community analyses such as indicator species analysis or diversity evaluations should be used to detect fertilizer effects.

A review on the role of predatory soil nematodes in the biological control of plant parasitic nematodes

Predatory nematodes feed on soil microorganisms including plant parasitic nematodes. They reduce populations of plant parasitic nematodes in virtually all soils because of their constant association with plant parasitic nematodes in the rhizosphere, and also release nutrients in plant-available forms, which may enable plants to better withstand nematode burden on their roots. Predation by nematodes of the orders Mononchida, Diplogasterida, Dorylaimida and Aphelenchida, has been studied but the data available in field/natural conditions are insufficient to conclude whether they are effective biocontrol agents of plant parasitic nematodes. However, among the different types of predators, diplogasterids are the most suited for biocontrol of nematodes, because of their short life cycles, easy culture, prey-specificity, chemotaxis sense and resistance to adverse conditions. This article summarizes progress to date and suggests ways to encourage the use of predatory nematodes as biocontrol agents in the management of plant parasitic nematodes.

Nematode communities in contaminated river sediments

Nematode communities of eight sites from three river catchments were investigated in terms of the genera composition, feeding types, and life-history strategists. The sampling sites showed a gradient of anthropogenic contamination with heavy metals and organic pollutants being important factors in differentiating the sites. Nematode community structure was related to sediment pollution and the hydro-morphological structure of the sampling sites. Heavily contaminated sites were characterized by communities with high relative abundances of omnivorous and predacious nematodes ( Tobrilus, c– p 3; Mononchus, c– p 4), while sites with low to medium contamination were dominated by bacterivorous nematodes ( Monhystera, Daptonema; c– p 2) or suction feeders ( Dorylaimus, c– p 4). The relatively high Maturity Index values in the heavily polluted sites were surprising. Nematodes turned out to be a suitable organism group for monitoring sediment quality, with generic composition being the most accurate indicator for assessing differences in nematode community structure.