Nematode Species Composition Research Articles

Faecal egg count reduction tests and nemabiome analysis reveal high frequency of multi-resistant parasites on sheep farms in north-east Germany involving multiple strongyle parasite species

Anthelmintic resistance in sheep parasitic gastrointestinal nematodes is widespread and a severe health and economic issue but prevalence of resistance and involved parasite species are unknown in Germany. Here, the faecal egg count reduction test (FECRT) was performed on eight farms using fenbendazole, ivermectin and moxidectin and on four farms using only moxidectin. A questionnaire was used to obtain data on management practices to potentially identify risk factors for presence of resistance. All requirements of the recently revised WAAVP guideline for diagnosing anthelmintic resistance using the FECRT were applied. Nematode species composition in pre- and post-treatment samples was analysed with the nemabiome approach. Using the eggCounts statistic package, resistance against fenbendazole, ivermectin and moxidectin was found on 7/8, 8/8 and 8/12 farms, respectively. No formal risk factor analysis was conducted since resistance was present on most farms. Comparison with the bayescount R package results revealed substantial agreement between methods (Cohen's κ = 0.774). In contrast, interpretation of data comparing revised and original WAAVP guidelines resulted in moderate agreement (Cohen's κ = 0.444). The FECR for moxidectin was significantly higher than for ivermectin and fenbendazole. Nemabiome data identified 4 to 12 species in pre-treatment samples and treatments caused a small but significant decrease in species diversity (inverse Simpson index). Non-metric multidimensional scaling and k-means clustering were used to identify common patterns in pre- and post-treatment samples. However, post-treatment samples were scattered among the pre-treatment samples. Resistant parasite species differed between farms. In conclusion, the revised FECRT guideline allows robust detection of anthelmintic resistance. Resistance was widespread and involved multiple parasite species. Resistance against both drug classes on the same farm was common. Further studies including additional drugs (levamisole, monepantel, closantel) should combine sensitive FECRTs with nemabiome data to comprehensively characterise the anthelmintic susceptibility status of sheep nematodes in Germany.

Nematode production in artificial ponds: a long-term perspective

Summary Nematodes are the most abundant multicellular animals on Earth and play an important role as intermediaries in energy fluxes. However, estimations of nematode biomass turnover and secondary production have been poorly defined for decades and it is difficult to reach a consensus about the importance of nematodes for ecosystem functioning. Here we monitored monthly the nematode species composition, abundance and biomass over 3-10 years in a set of artificial urban ponds, and we used different allometric models to estimate biomass turnover and secondary production. During the first 3 years of colonisation of the pond bottom, the nematode community was rather species-poor and mostly composed of small bacterivorous species (Monhysterids); however, the community quickly reached impressive numbers (up to 21 million individuals m−2) achieving a maximum annual production of 3.8-11.6 gC m−2 year−1 depending on the allometric model used for estimation. However, over the long-term (3-10 years), abundance and community structure eventually became dramatically altered by anoxic events occurring in one pond, dampening nematode production to low levels (0.3-0.6 gC m−2 year−1) without clear resilience. The comparison of models helped us to formulate general recommendations in order to popularise the use of nematode secondary production as a useful ecosystem diagnostic tool. Overall, results indicated that under good conditions of oxygenation nematodes are a highly productive component of the zoobenthos of ponds. We also discussed the consequences of this finding for sustainable pond aquaculture, as nematodes constitute an important local and nutritive resource for juveniles of economically important fish, such as carp and tilapia.

Long‐term grazing intensity by reindeer alters the response of the soil micro‐food web to simulated climate change in subarctic tundra

Top–down control by nematodes over soil microorganisms – considered to be stronger over bacteria than over fungi – may dampen microbial responses to global changes in tundra. To test whether large grazers alter the responses of belowground trophic networks to global changes, we employed factorial warming and nitrogen fertilization treatments in adjacent sites with different reindeer grazing intensities for the past 50 years. Lightly grazed tundra is dominated by dwarf shrubs and a more fungal‐based microbial community, while in heavily grazed tundra the high reindeer densities during autumn migration have induced a shift into graminoids and a more bacterial‐based microbial community. We analysed the soil micro‐food web (i.e. the nematode density, trophic structure and species composition) as well as fungal, bacterial and total phospholipid fatty acids (PLFAs) after four growing seasons of warming and fertilization both before and during reindeer migration. We predicted that bacterivore densities are higher and fungivore densities lower under heavy than light grazing (i.e. nematode populations before migration reflect grazing effects via the base of the food web), whereas reindeer migration induces a negative impact on nematode densities under heavy grazing (disturbance by trampling is the driving factor). We further predicted that nematodes negate treatment effects on microbial biomass to a stronger extent in the bacterial‐based heavily grazed tundra than in the fungal‐based lightly grazed tundra. Fungivore densities were higher under light than under heavy grazing, but nematodes did not respond to trampling. Warming increased fungivores and the fungal PLFAs irrespective of grazing and timing but, under heavy grazing, it increased bacterivores while the bacterial PLFAs remained steady. Fertilization increased carnivores and influenced nematode species composition, diversity and maturity interactively with warming. Our data suggest that large grazers affect tundra soil nematodes via bottom–up effects through microbial community composition and biomass, which in turn may alter the strength of their top–down control over soil bacteria under climate warming.

Variations of Free-Living Marine Nematode’s Taxonomic Structure and Functional Traits in Contrasting Sandy Beach Habitats

In the present study, two temperate sandy beaches, which were located on the coast of different seas with different hydrological states, were selected to investigate the variations and drivers of the taxonomic structure and functional traits of the free-living marine nematode. According to the present study, Xyalidae and Chromadoridae were widely observed in both locations, but the species composition and functional traits were not completely the same. In fine sands, non-selective deposit feeders or colonizers (nematodes with c-p = 2) were far more quantitatively than other functional traits, suggesting a relatively restricted range of functional traits. The increased microhabitat heterogeneity in coarse sands can support species with more diverse functional traits. Chl-a was the most prominent variable that significantly related to nematode species composition and functional traits at XB sites. Nematode data were closely related to temperature or temperature-related environmental factors, such as DO and salinity, at GB sites.

Disentangling the Effect of Seasonal Dynamics on Meiobenthic Community Structure From River Matla of Sundarbans Estuarine System, India

In estuarine sediment, meiobenthos serve as an excellent candidate to perform a range of ecosystem services. However, even though the taxonomic sufficiency of meiobenthos in detecting spatiotemporal gradients is well recognized, very little is known about their functional attributes in response to environmental descriptors. To bridge this knowledge gap, the taxonomic structure and trait-based functional diversity patterns of meiobenthic assemblage, focusing on nematode species composition, were assessed for the first time from the unexplored central sector of Sundarbans Estuarine System (SES). Sediment samples were collected seasonally (monsoon, winter, spring, and summer) selecting a total of eight stations across River Matla (the widest and longest river of SES). Distinct seasonal successional patterns had been observed in meiobenthic abundance modulated by seasonal alteration in the sedimentary environment (PERMANOVA, p < 0.05). Our study revealed a strong preponderance of meiobenthic density in spring (2978 ± 689.98 ind. 10 cm–2) and lowest during monsoon (405 ± 51.22 ind. 10 cm–2). A total of 11 meiobenthic taxa were identified with the dominance of nematodes. Altogether, 79 species of nematode belonging to 22 families had been identified across the entire study area and nematode assemblage was dominated by Sabatieria praedatrix, Sphaerolaimus balticus, Desmodora communis, Dorylaimopsis punctata, and Daptonema hirsutum. Principal component analysis depicted a distinct separation of seasons with reference to environmental variables. Distance-based redundancy analysis delineated that meiobenthic communities were mainly structured by organic matter, salinity, and dissolved oxygen concentration. Biological trait analyses of nematode assemblages were applied to gather the ecological information based on morphological and ecological characteristics. The most common morphotypes were slender body shape, clavate tail shape, striated cuticle pattern, and non-selective deposit feeders with colonizing abilities of 2–3 (c–p score in a scale from 1 to 5). Results from BIO-ENV showed that sediment organic matter and dissolved oxygen played overriding roles in shaping the functional compositions of nematodes. Thus, the characterization of meiobenthos and nematode assemblages in the context of taxonomic as well as functional attributes represents a first step toward building of baseline data which could help to evaluate the ecological status of SES and direct future research priorities concurrently.

A 4 year observation of gastrointestinal nematode egg counts, nemabiomes and the benzimidazole resistance genotypes of Teladorsagia circumcincta on a Scottish sheep farm

Anthelmintic resistance threatens the sustainability of sheep production globally. Advice regarding strategies to reduce the development of anthelmintic resistance incorporates the outcomes of modelling exercises. Further understanding of gastrointestinal nematode species diversity, and population dynamics and genetics (which may vary between species) is required to refine these models; and field studies combining faecal egg outputs, species composition and resistance genetics are needed to calibrate them. In this study, faecal samples were taken from ewes and lambs on a commercial farm in south-eastern Scotland at approximately 3 t-4 week intervals between spring and autumn over a period of 4 years. Faecal egg counts were performed on these samples, and L3 were collected from pooled coprocultures. Deep amplicon sequencing was used to determine both the species composition of these L3 and the proportions of benzimidazole-resistant single nucleotide polymorphisms in the isotype-1 β-tubulin locus of the predominant species, Teladorsagia circumcincta L3. Despite consistent management throughout the study, the results show variation in gastrointestinal nematode species composition with time and between age groups, that was potentially associated with weather conditions. The F200Y benzimidazole resistance mutation is close to genetic fixation in the T. circumcincta population on this farm. There was no evidence of variation in isotype-1 β-tubulin single nucleotide polymorphisms frequency between age groups, and no genetic evidence of reversion to benzimidazole susceptibility, despite targeted benzimidazole usage. This study highlights the need to include speciation when investigating gastrointestinal nematode epidemiology and anthelmintic resistance, and serves as an example of how genetic data may be analysed alongside species diversity and faecal egg counts, when markers for other anthelmintic classes are identified.

Impact of historical sulfide mine tailings discharge on meiofaunal assemblages (Portmán Bay, Mediterranean Sea)

Portmán Bay is one of the most contaminated and chronically impacted coastal marine areas of the world. Here, from the 1957 to 1990, about 60 million tons of mine tailings from the processing of sulfide ores were dumped directly at the shoreline. The resulting deposit provides a unique opportunity to assess the impact of mine tailings on coastal marine ecosystems after ca 30 years since the discharge has ceased. We investigated meiofaunal abundance, biomass and biodiversity along a gradient of metal concentration that overlaps with a bathymetric gradient from 30 to 60 m depth. Despite the localized presence of extremely high concentration of metals, the bay was not a biological desert, but, nevertheless, was characterized by evident signs of impact on benthic diversity. Meiofaunal variables increased significantly with decreasing metal contamination, eventually reaching values comparable to other uncontaminated coastal sediments. Our results show that mine tailings influenced the spatial distribution of meiofaunal taxa and nematode species composition. In particular, we report here that the bay was characterized by the dominance of nematode opportunistic species tolerant to high metal concentration. The effects of mine tailing discharge on meiofaunal biodiversity and composition were still evident ca 30 years after the end of the mining activities. Overall, this study provides new insights on the potential impact of mine tailings disposal and metal contamination in coastal sediments, and, can also contribute to predict the potential long-term consequences of ever-expanding deep-sea mining industry on benthic environments.

Seasonal distribution of abundance, biomass and secondary production of free-living nematodes and their community composition in different stream micro-habitats

Summary The nematode communities of four different micro-habitats in an unpolluted first-order stream were investigated over a 13-month period in a study of the sediment and the biofilms on dead wood, macrophytes and leaf litter. Nematode abundances, biomass and secondary production were analysed, together with the species composition, proportion of feeding types and diversity of the nematode communities of the micro-habitats. Differences between the investigated micro-habitats in terms of seasonal variations, species composition, proportion of feeding types and diversity were expected. The annual mean values of nematode abundance, biomass and secondary production differed significantly between the micro-habitats. Abundances were highest on dead wood, whereas biomass and secondary production were highest in sediment. In the sediment and on leaf litter, nematode abundance and biomass showed pronounced seasonal patterns. The largest contribution to the total secondary production of the stream was from sediment nematodes. In total, 108 nematode species were detected in the micro-habitats during the 13-month study. Comparisons between them revealed differences in nematode species composition. The annual mean species number was significantly higher in sediment and on leaf litter than on dead wood and macrophytes, whereas the annual mean Shannon-Wiener index was significantly higher in sediment than at all other micro-habitats. All micro-habitats in the studied stream, as well as the stream as a whole, were dominated by nematode species belonging to the deposit feeders. Our study clearly showed that the composition of nematode communities from different micro-habitats within a single stream reach can differ markedly.

Impact of historical contamination on meiofaunal assemblages: The case study of the Bagnoli-Coroglio Bay (southern Tyrrhenian Sea)

The effects of contaminants on marine organisms have been documented since decades, but the long-term responses and recovery rates of benthic communities to mixtures of contaminants, several years after the cessation of industrial activities, need to be further investigated. Bagnoli-Coroglio Bay (Gulf of Naples, Tyrrhenian Sea) is a typical example of historically contaminated coastal area due to industrial activities stopped at the beginning of nineties. In the present study we carried out a fine spatial scale analysis of the distribution of meiofaunal (and nematodes) assemblages along five bathymetric transects located at increasing distance from the historical source of contamination in relation with the polycyclic aromatic hydrocarbon and heavy metal concentrations present in the sediment. Meiofaunal abundance and biomass changed widely along transects but independent from the distance from the source of contamination. Even when the contamination levels were expected to induce significant detrimental biological consequences, meiofaunal abundance and biomass were similar to those reported in unpolluted benthic coastal areas worldwide. Conversely, biodiversity in terms of meiofaunal taxa richness was generally low (range: 5–8 taxa in 12 of the overall 15 stations investigated). This was explained by the lack of sensitive groups such as ostracods, gastrotrichs and tardigrades commonly encountered in benthic coastal ecosystems, thus reflecting an overall poor/moderate environmental quality of the investigated area. Nematode (structural and functional) diversity was also low, particularly at stations characterized by higher contamination levels. At the same time, nematode species composition did not change significantly among stations suggesting a widespread effect of contaminants able to reduce the variability (i.e., turnover diversity) within the assemblages of the whole study area. Overall, our results indicate that even decades after the cessation of contaminant emissions, benthic biodiversity was affected in terms of both meiofaunal taxa and nematode species. These findings strongly reinforce the call for reducing sources of chronic pollution in marine ecosystems and provide new insights for a better understanding of the ecological recovery of historically contaminated marine environments.

Response of a nematode community to the fungicide fludioxonil in sediments of outdoor freshwater microcosms compared to a single species toxicity test

When entering aquatic ecosystems, hydrophobic organic chemicals like the fungicide fludioxonil partition to the sediment compartment where they pose potential risks to benthic invertebrates. To assess the ecological risk for sediment-dwelling invertebrates, nematodes are a suitable organism group, as they are abundantly present and possess key positions in the benthic food web. Therefore, the toxicity of the fungicide fludioxonil to nematodes was assessed in a standardized sediment toxicity test with Caenorhabditis elegans (ISO 10872), as well as in an outdoor sediment-spiked microcosm test system. In the microcosms, effects on the nematode species composition were studied, while exposure concentrations of fludioxonil were monitored in total sediment and pore water. Toxic effects on nematodes were better predicted using concentrations in pore water than total sediment concentrations. In laboratory single species tests, fludioxonil showed considerably lower toxicity in spiked field-collected sediment, compared to artificial ISO-sediments. Applying an assessment factor of 10 to the C. elegans 96-h EC10, a Tier-1 RACNematode of 7.99 mg kg−1 dry artificial sediment (corresponding to 69 μg l−1 in pore water) appeared to be protective for nematode communities in microcosms that showed no response in total abundance and species composition up to 39.9 mg fludioxonil kg−1 dry sediment (corresponding to 392 μg l−1 in pore water).

Does vertical distribution of meiobenthic community structure differ among various mangrove habitats of Sundarban Estuarine System?

Mangroves are the most productive environments that play significant ecological and socioeconomic roles. For the first time we investigated vertical stratification of meiofaunal community and nematode species composition from the sediments of five mangroves (Aegiceras corniculatum, Bruguiera gymnorrhiza, Avicennia alba, Rhizophora mangle and Sonneratia caseolaris) at Bali Island in the worlds’ largest mangrove ecosystem of Sundarbans, India. Among different mangrove species, S.caseolaris had the highest density of meiofauna with the lowest in B. gymnorrhiza. A total of eight taxa were recorded from the sediment of different mangrove habitats. In terms of percentage composition, free-living nematodes dominated followed by harpacticoid copepods, kinorhynch, ostracods, foraminifera, polychaete, halacarid mite and bivalve juvenile. The vertical profile of meiofaunal composition suggested upper 3–4 cm harboured 90% of total meiofauna, although they were present up to 15 cm depth. Environmental variables explained meiofaunal community structure. Availability of food sources such as phaeopigments, Chlorophyll a, organic carbon and sediment texture controlled meiofaunal distribution. The nematode fauna consisted of 52 species belonging to 39 genera and 20 families. The trophic structure of nematode taxa revealed a community dominated by epistrate feeders (2A) followed by selective deposit feeders (1A). Moreover, marine nematode genera were used to test Maturity Index (MI), life strategy or biological traits (i.e. c–p classes) and Index of Trophic Diversity (ITD) for assessing ecological health. Higher MI among different mangrove vegetation indicated a stable environment; moreover, biological trait analysis showed that mangrove sediments were dominated by r-strategists. Lower values of ITD index revealed a proportionate occurrence of trophic diversity in nematode communities among different vegetation. In the current context of habitat destruction and anthropogenic perturbations, investigation of ecological interactions between mangroves and meiofauna would be imperative for ecosystem monitoring and sustainable development in future.

Effects of the water-soluble fraction of a crude oil on estuarine meiofauna: A microcosm approach

Although soluble hydrocarbons persist for only hours to days in aquatic environments, they potentially pose a high toxicity to aquatic biota. Here we investigate effects of the water-soluble fraction (WSF) of crude oil on estuarine meiofauna, with special focus on nematodes. Copepods and amphipods were the most sensitive taxa, disappearing almost completely within 3 weeks after exposure. In nematodes, we observed mostly sublethal short-term effects of WSF, such as changes in feeding-type composition and age structure. In the longer term (months), total nematode density and species composition were significantly affected, whereas different diversity indices did not exhibit significant responses. Deposit-feeding and predatory nematodes were the most affected feeding types. Nevertheless, sensitivity was species-specific, with sometimes opposing responses between even congeneric species. Our results demonstrate the need to assess WSF effects on communities at the species level and over time periods well exceeding the residence time of the WSF in the environment.

Effects of the water-soluble fraction of a crude oil on freshwater meiofauna and nematode assemblages

Oil water-soluble fractions (WSFs) compounds have low persistence in water; evaporating in a matter of hours to days. Nonetheless, they pose high toxicity to exposed biota. Their effects may be instantaneous or delayed, affecting, respectively, mainly survival vs growth and reproduction. We investigated the effects of crude oil WSFs on freshwater meiobenthos, with a focus on nematode assemblages, in community microcosm experiments lasting 15 weeks. Treatments consisted of the application of different concentrations of oil WSFs, i.e. high (100%) medium (50%) and low (10%), and effects were assessed one, three, nine and 15 weeks after contamination, allowing us to detect both short-term and lasting effects of oil-WSF. Additionally, we compared the effects of a single contamination event with those of a so-called ‘constant’ oil-WSF contamination where we replenished evaporated water with water containing the medium concentration of oil WSF. Next to nematodes, the most abundant meiofaunal taxa were rotifers, gastrotrichs, oligochaetes and tardigrades. Total abundance, different diversity indices, the composition of feeding-types and the age structure were investigated in the assessment of direct oil effects on the structure of nematode assemblages. Limited immediate effects were observed, except for a significant decrease of the index of taxonomic distinctness, which already appeared in the first week. Significant impacts on total nematode abundance, diversity and species composition only became apparent after 9–15 weeks of incubation, indicating that delayed effects of a single exposure are far more pronounced than instantaneous effects. Moreover, for most response variables, the strongest impacts were not observed in the highest-concentration treatment, but in a medium-concentration treatment with regular replenishment of oil WSF, suggesting that internal exposure may be important in generating effects. Furthermore, the predictability of the sensitivity of individual species was sometimes poor, which may not only result from these species' sensitivities, but also from alterations in interspecific interactions in polluted communities. Further toxicity tests should be carried out in order to unravel the main modes of action of crude oil WSF which lead to the observed long-term sublethal effects on nematode communities.

Biodiversity and distribution of meiofauna in the Gioia, Petrace and Dohrn Canyons (Tyrrhenian Sea)

Habitat heterogeneity is a major structuring agent of benthic assemblages promoting high turnover in species composition and ultimately contributing to overall higher diversity. Submarine canyons, a pervasive feature of the continental margins worldwide, increase habitat heterogeneity at multiple spatial scales. In the present study, we test the hypothesis that different topographic structures or/and food sources controlling the abundance, biomass and biodiversity (using meiofauna and nematodes as a model study) in canyon systems. To do so, we compared different topographic structures: canyon edge, thalweg and axis, and the upper shelf and open slope in the Gulf of Gioia (Gioia and Petrace Canyons) and in the Gulf of Naples (Dohrn Canyon) (Tyrrhenian Sea) at different depths. Our results suggest that meiofaunal abundance and biomass are generally higher in the canyon thalwegs than in the canyon edge or adjacent open slopes at regional scale. This pattern is not always confirmed for biodiversity and when thalwegs are compared to different topographic structures within the Gioia Canyon system. In our study, the role of food quantity and quality is preeminent to explain the spatial distribution of meiofaunal variables among different topographic structures at 200-m while habitat heterogeneity become relevant at 500-m and within the Dohrn Canyon. In Gioia and Petrace Canyons we observed a high food availability is associated to specific topographic structures (thalwegs) that influenced the meiofaunal abundance and diversity distribution and nematode diversity and species composition. Each topographic structure shows a high number of exclusive species that contributes to a high species turnover and high overall biodiversity in all canyon systems. Changes in nematode composition determine also differences in the functional diversity (trophic guilds composition) and life strategy of the nematode assemblages. Our findings reveal that the presence of different topographic structures influences the spatial distribution of food quality and quantity that determine the presence of exclusive taxa and species enhancing both local and regional diversity.

Species composition and structure of complex of phytonematodes of ornamental plants under conditions of Kiev Goloseevskiy park

The purpose of the research: study of fauna phytonematodes of ornamental crops. Materials and methods. Studies were conducted in 2016-2017 years in Kiev Goloseevskiy park, Ukraine. Materials for studies were samples of soil, plants, larvae and adult nematodes. Production of temporal and permanent preparations, determination of nematode species composition were conducted according to common methods. Results and discussion. 41 phytonematode species belonging to 29 species, 16 families and 5 series were found in rhizosphere of ornamental plants of Goloseevskiy park. According to taxonomic structure 49% species of ornamental plant phytonematode complex belong to Tylenchidae, 36% - to Rhabditida, 7% - to Dorylaimida, 4% - to Enoplida and 4% - to Araeolaimida. It is reasonable to divide species of nematodes found in rhizosphere of plants into 4 groups: phytohelminths, micohelminths, saprobionts and predaceous species. Phytohelminths are 11 species, micohelminths are 7 species, saprobionts are 20 species and 2 species are predaceous speciesof nematodes. Cassagnau index was used in order to determine the state of dominance of dispersed species of nematodes (Cassagnau, 1947). According to this parameter Helycotylenchus dihystera, Aphelenchoides fragarie and Ditylenchus dipsaci were the predominate phytoparasitic species. The following species which we often found were: Tylenchorhynchus dubius, Pratylenchus penetrans, P. pratensis, D. destructor, Paratylenchus nanus, Rotylenchus robustus, A. ritzemabosi, species which we found rarely was Longidorus elongatus.

Factors influencing the nematode community during composting and nematode-based criteria for compost maturity

Pilot studies indicate that shifts in the nematode species composition, life strategies and feeding behavior during composting appear to be fairly consistent and, therefore, promising as a potential tool to assess compost maturity. However, this has been only based on a limited number of, mainly, non-replicated observations. In this study, we tested whether the nematode community succession patterns are recurrent for parallel processes and assessed the relationship between the changes in the nematode community and potential important variables (i.e., temperature, duration of composting and the microbial community). The nematode and microbial community of three simultaneously running Controlled Farm Composting and a reference Green Waste composting process were analyzed through time. Bacterial-feeding enrichment opportunists were most numerous during and directly after the heat peaks. Subsequently, the bacterial-feeding/predator community dominated and the fungal-feeding nematodes became more dominant during maturation, confirming general community patterns from previous experiments. Nematode abundances significantly fluctuated with temperature and the relative abundance of fungal-feeding nematodes increased as the duration of the curing process increased. The amount of fungal-feeding nematodes was associated significantly with both duration of composting and temperature, and the F/(F+B) ratio was only significantly associated with duration of composting. Based on these results, and additional data from an industrial reference compost process and on available literature, a Nematode-based Index of Compost Maturity (NICM) is proposed, combining four nematode-based criteria (i.e., nematode abundance, F/(F+B) ratio, the presence of more than one fungal-feeding taxon and the presence of diplogasterids). Nevertheless, the NICM should be considered as work in progress which should be tested for a wider range of composts from diverse feedstock mixtures, locations (sites) and composting techniques, to validate the use of the index and allow more reliable interpretation of particular values of this index.

Insights into the benthic communities response to the inflow of Black Sea mesotrophic waters in the North Aegean Sea

The effects of the Dardanelles inflow of buoyant, modified Black Sea waters (BSW) of low salinity and temperature, on the meio- and macrobenthic communities of the north Aegean ecosystem was investigated during two cruises in October 2013 and March 2014. Sediment samples were collected from two stations subjected to the BSW effect, one shallow and one deep north of the Dardanelles Straits, and from two stations of similar bathymetry, which were considered to be outside the influence of BSW and were located to the south of the Dardanelles Straits. Results suggest that there is an effect of the BSW on benthos, as both meiofaunal and macrofaunal standing stocks were lower at the most distant, and therefore least affected from the inflow, station, and higher at the station of similar bathymetry which was affected the most by the BSW inflow. Univariate and multivariate non-parametric analyses (nMDS, PERMANOVA) provided further support, indicating differences between the two areas (North vs. South) in the case of the deep stations, while differences between depth categories were evident in the area outside the BSW influence zone. Distance-based linear modeling (DISTLM) indicated that meiofauna correlated with proxies of food availability and sediment characteristics. Macrofauna, on the other hand, showed a rather high significant correlation with depth only. Nematode species composition was statistically significant different between depth categories only, yet the nMDS ordination clearly separated the deep southern station from the rest, with non-selective deposit feeders dominating the stations under the influence of the BSW, and epistratum feeders being important at the stations outside the influence of the BSW. It is concluded that both the meiofaunal and macrofaunal communities at the northern stations benefit from a constant input of high amounts of organic matter to the seafloor, while those at the southern area may be occasionally affected by the thermohaline BSW front, which may reach as far as the southern stations, resulting in higher but rather unpredictable organic enrichment.

Effect of the Hebei Spirit oil spill on intertidal meiofaunal communities in Taean, Korea

In December 2007, approximately 10,900tons of oil from a crude carrier spread rapidly onto the coast of South Korea. We studied the effects of oil on meiofauna by comparing two contaminated intertidal sites with an uncontaminated site. During 2008–2009, the density of meiofauna fluctuated among the contaminated sites but did not vary by season. Seasonal changes in density were observed at contaminated sites 3years after the oil accident. Meiofauna appeared to be more sensitive to oil pollution stress at the more heavily contaminated site than at the less contaminated site. CLUSTER analysis showed that meiofauna communities in the 3years immediately following the accident significantly differed from those sampled later. A non-metric multidimensional scaling analysis showed that nematode species composition in the first month after the accident significantly differed from those sampled later. Long-term monitoring is needed to assess the effects of oil on the meiofaunal community.

Effect of anthelmintic treatment strategy on strongylid nematode species composition in grazing lambs in Scotland

BackgroundRefugia based anthelmintic protocols aim to reduce the rate of development of anthelmintic resistance in gastrointestinal nematodes (GIN). Previous studies have illustrated the impact of different drenching regimes on drug efficacy and animal growth; however, the impact on nematode populations has yet to be characterised within natural infections. This study investigated the changes in species composition of GIN throughout the grazing season, following implementation of four different ivermectin drenching regimes over six years: neo-suppressive monthly treatment (NST), targeted selective treatment (TST), strategic prophylactic treatment (SPT) and treatment upon observation of clinical signs (MT).MethodsLambs were grazed on one of eight replicate paddocks each grazing season following treatment regimes assigned in year 1. Faecal samples were collected fortnightly from all animals and hatched to first stage larvae (L1). DNA was extracted from individual L1 and a multiplex PCR assay targeting the internal transcribed spacer 2 (ITS2) region of Teladorsagia circumcincta, Trichostrongylus spp. and Haemonchus contortus conducted. Other species were identified using species-specific PCR. Worm-naïve tracer lambs were grazed on the paddocks at the start and end of each grazing season and adult worms recovered at post mortem to investigate the parasite population on pasture.ResultsResults showed an overall decrease in species diversity in egg output from the NST group which occurred within a single grazing season and was consistent throughout the experiment. Species diversity was protected over six years in groups implementing TST, SPT and MT treatment regimes, designed to offer refugia. The expected shift in species prevalence throughout the season from Teladorsagia to Trichostrongylus was observed in all but the NST group where only Teladorsagia spp. were recovered from trial lambs by the end of the experiment. Worm burdens indicated the presence of several species at relatively low abundance on pasture in the NST group in 2011. However, these species were not represented in egg output from trial lambs, probably due to the frequent anthelmintic treatment administered throughout the grazing season.ConclusionThe molecular methods utilised here worked well. The comparable results of the three refugia-based treatment regimes suggest that nematode diversity can be maintained using part or whole group treatments if a rich supra-population of parasites are available to re-infect animals post treatment.

The Effect of Dreissena polymorpha on Bacterioplankton, Nematode Fauna and their Relations to Environmental Factors in Ogosta Reservoir (Danube Basin)

Abstract Spatial, seasonal, and annual bacterioplankton dynamics in recently infested by the species Dreissena polymorpha Ogosta Reservoir were studied for the first time during three year period. Bacterioplankton total number was higher in spring in ecotone zones, than in summer at thermocline. NH4-N, PO4-P, turbidity, dissolved oxygen, COD and chlorophyll-a correlate positively, while transparency and Ca2+ negatively with bacteria. Nematode species composition, included 22 species studied (13 rarely found and Rhabditis brevispina new for Bulgaria) belonging to nine families. The D. polymorpha impact is positive on nematodes and phytoplankton, negative on zooplankton and bacterioplankton, but weak positive on larger bacteria, rods and attached bacteria.