Dominant Nematode Research Articles

Nematodes Associated with Two Species of Mentha (Lamiaceae) in Balochistan, Pakistan


 Nematodes associated with Mentha spicata L. and Mentha longifolia L. were investigated in Balochistan in various localities so as to assess the variation in density of different nematode species found in the rhizosphere. Ten species of nematodes were found associated with Mentha spicata while four species were found in the rhizosphere of M. longifolia. Significant differences in nematode density were recorded (p at the most p < 0.01). The dominant nematodes associated with Mentha spicata were Pratylenchus projectus and Merlinius khuzdarensis while those associated with Menthe longifolia were Xiphinema americanum and Pratylenchus thornei.
 

Are nematodes costly to fig tree–fig wasp mutualists?

AbstractMost mutualisms are exploited by parasites, which must strike an evolutionary balance between virulence and long‐term persistence. Fig‐associated nematodes, living inside figs and dispersed by fig wasps, are thought to be exploiters of the fig–fig wasp mutualism. The life history of nematodes is synchronized with the fig development and adapted to particular developmental characteristics of figs. We expect host breeding systems (monoecious vs. gynodioecious figs) and seasonality to be central to this adaptation. However, the details of the adaptation are largely unknown. Here, we conducted the first field surveys on the prevalence of nematodes from monoecious Ficus microcarpa L.f. (Moraceae), gynodioecious Ficus hispida L.f., and their pollinating fig wasps in two seasons and two developmental stages of figs in Xishuangbanna, China. We followed this up by quantifying the effects of nematodes on fitness‐related traits on fig wasps (e.g., egg loads, pollen grains, and longevity) and fig trees (seed production) in gynodioecious F. hispida. The magnitude of nematode infection was compared between pre‐ and post‐dispersal pollinators to quantify the probability of nematodes being transported to new hosts. Our results showed that Ficophagus microcarpus (Nematoda: Aphelenchoididae) was the only nematode in F. microcarpa. In F. hispida, Martininema guangzhouensis (Nematoda: Aphelenchoididae) was the dominant nematode species, whereas Ficophagus centerae was rare. For both species of Ficus, rainy season and inter‐floral figs had higher rates of nematode infection than the dry‐hot season and receptive figs. Nematodes did not affect the number of pollen grains or egg loads of female wasps. We did not detect a correlation between seed production and nematode infection. However, carrying nematodes reduced the lifespan and dispersal ability of pollinator wasps, indicating higher rates of post‐emergence mortality in infected fig wasps. Severely infected fig wasps were likely ‘filtered out’, preventing the overexploitation of figs by wasps and stabilizing the interaction over evolutionary time.

Sensitive and rapid detection of Ortleppascaris sinensis (Nematoda: Ascaridoidea) by loop-mediated isothermal amplification.

Ortleppascaris sinensis is the dominant nematode species infecting the gastrointestinal tract of the captive Chinese alligator, a critically endangered species. Gastrointestinal nematode infection may cause a loss of appetite, growth, a development disorder, and even mortality in alligators, especially young ones. This research first establishment a loop-mediated isothermal amplification (LAMP) assay in rapidly identifying O. sinensis, upon the basis of the complete internal transcribed spacers (ITS) gene. Eight sets of primers were designed for recognition of the unique conserved ITS gene sequences, and one set was selected to be the most suitable primer for rapid detection. The specific as well as the sensitive features of the most appropriate primer in LAMP reactions for O. sinensis, and feces specimens of Chinese alligators suffering from O. sinensis were determined. Turbidity monitoring and Te Visual Reagent methods were used for determining negative and positive consequences. According to this study, amplification and visualization of the target DNA could be realized through two detection approaches during 50 min at 65 °C isothermal temperature. The sensitivity of LAMP was a detecting limitation of 3.46 pg/µl DNA. No cross-reactions were found between O. sinensis and any other of the nine heterologous nematode parasites, which shows the outstanding specific features of the primers. The LAMP assay could also perform a detection of target DNA of O. sinensis in the feces samples of Chinese alligators. This LAMP assay is useful for directly detecting O. sinensis in the Chinese alligator breeding centers, particularly due to its rapidity, simplicity and low cost.

Diversity of Soil Nematode in Utilization Block Integrated Educational Conservation Forest, Wan Abdul Rachman Great Forest Park

Change of land forest in Wan Abdul Rachman Forest Park became agroforestry, affect of cover condition and decrease the content of soil matter. Nematode was one of the soils biotas that can be used as an indicator of change in the soil status. The aim of study is to know the community and diversity of nematodes on the Utilization Block, Integrated Educational Conservation Forest, Wan Abdul Rachman Great Forest Park. The research was conducted in April to May 2018. The soil samples were taken on arboretum one, arboretum two, arboretum three and arboretum four in Integrated Educational Conservation Forest, Wan Abdul Rachman Great Forest Park. Nematode observations were conducted in the Plant Pests Laboratory, Faculty of Agriculture, University of Lampung. Nematodes was identified to genus level based on morphological traits. The analysis used were including the index of diversity, dominance and similarities between genus arboretum. The results showed that there were 30 genus of nematode consists of 19 plant parasitic nematode genera, six nematoda bacterial-feeding, three nematode fungal-feeding and two predator nematodes. The dominant nematode genera were Criconomella, Helycotylenchulus and Rotylenchulus. The abundance of nematodes ranges from 171-617 individuals/300cm3 soil. The diversity of soil nematodes based on the Shannon-Wienner index ranges from 2,47 – 2,80. The Shannon-Whienner Index criteria were classified as moderate. The Simpson Index ranges from 0,89 – 0,93. The highest similarity index genus in arboretum three and four with a value of 0,81 and the lowest in arboretum two and three which is 0,54. Key words: nematodes community, Integrated Educational Conservation Forest, Wan Abdul Rachman Great Forest Park

Responses of an abyssal meiobenthic community to short-term burial with crushed nodule particles in the south-east Pacific

Abstract. Increasing industrial metal demands due to rapid technological developments may drive the prospection and exploitation of deep-sea mineral resources such as polymetallic nodules. To date, the potential environmental consequences of mining operations in the remote deep sea are poorly known. Experimental studies are scarce, especially with regard to the effect of sediment and nodule debris depositions as a consequence of seabed mining. To elucidate the potential effects of the deposition of crushed polymetallic nodule particles on abyssal meiobenthos communities, a short (11 d) in situ experiment at the seafloor of the Peru Basin in the south-east Pacific Ocean was conducted in 2015. We covered abyssal, soft sediment with approx. 2 cm of crushed nodule particles and sampled the sediment after 11 d of incubation at 4200 m water depth. Short-term ecological effects on the meiobenthos community were studied including changes in their composition and vertical distribution in the sediment as well as nematode genus composition. Additionally, copper burden in a few similar-sized but randomly selected nematodes was measured by means of micro X-ray fluorescence (µXRF). At the end of the experiment, 46±1 % of the total meiobenthos occurred in the added crushed nodule layer, while abundances decreased in the underlying 2 cm compared to the same depth interval in undisturbed sediments. Densities and community composition in the deeper 2–5 cm layers remained similar in covered and uncovered sediments. The migratory response into the added nodule material was particularly seen in polychaetes (73±14 %, relative abundance across all depth layers) copepods (71±6 %), nauplii (61±9 %) and nematodes (43±1 %). While the dominant nematode genera in the added nodule material did not differ from those in underlying layers or the undisturbed sediments, feeding type proportions in this layer were altered, with a 9 % decrease of non-selective deposit feeders and an 8 % increase in epistrate feeders. Nematode tissue copper burden did not show elevated copper toxicity resulting from burial with crushed nodule particles. Our results indicate that burial with a 2 cm layer of crushed nodule particles induces changes in the vertical structure of meiobenthos inside the sediment and an alteration of nematode feeding type proportions within a short time frame of 11 d, while nematode tissue copper burden remains unchanged. These findings considerably contribute to the understanding of the short-term responses of meiobenthos to physical disturbances in the deep sea.

Diversity of Arthropods and Parasitic Nematodes Population in Intercropping Patterns of Robusta Coffee


 
 
 Shade plants affect the microclimates around the plants which directly affect the population of arthropods, especially insects. Therefore, this research was needed to analyze the diversity and role composition of insects in Robusta coffee plantations based on different intensity of shade plants. Samplings of insects and parasitic nematodes were conducted in intercropping patterns of Robusta coffee namely mixed intercropping patterns, coffee-pepper intercropping patterns and coffee-banana intercropping patterns. In each intercropping pattern of Robusta coffee, samplings were conducted as much as ten plants using random sampling. Data analysis was done by calculating the Shannon-Wiener diversity index (H') and evenness index (E). The results showed that diversity index in all Robusta coffee intercropping patterns were < 3, indicating that the diversity of insects in all intercropping patterns was relatively. Insect diversity in coffee-pepper inter- cropping pattern is found higher than the one in either mixed intercropping pattern or coffee-banana intercropping patterns. Out of those intercropping patterns, insects from Formicidae family of Hymenoptera order was found to be the most dominant insects. The composition of insects in all of those three intercropping patterns has been mainly dominated by insects from the family of Formicidae and Hymenoptera order since they are natural enemy insects. Pratylenchus coffeaehas been confirmed as the most dominant nematode species in the three Robusta coffee intercropping pattern. P. coffeae had the highest population average of 3279 in coffee-pepper intercropping pattern.
 
 

Salivary IgA: A biomarker for resistance to Teladorsagia circumcincta and a new estimated breeding value

Teladorsagia circumcincta is the dominant nematode of sheep in cool, temperate climates. Faecal nematode egg counts (FEC) are widely used to identify the intensity of infection and as a measure of host resistance to nematodes. However due to density-dependent effects on worm fecundity the relationship between FEC and worm burden is not linear. In addition collecting FEC data is challenging on a practical level and there is a need for more reliable markers of resistance. There are two major known mechanisms of immunity to T. circumcincta: IgE against third stage larvae (L3) and IgA against fourth stage larvae (L4), which inhibits parasite growth. In this study salivary IgA responses were measured in over 5000 animals against L3 antigen by Enzyme Linked Immunosorbent Assay (ELISA). Antigen-specific IgA levels were negatively correlated with FEC (r=−0.26, SE = 0.02) and were heritable (h2 = 0.16, SE = 0.04) indicating that they can be used to identify resistant animals suitable for inclusion in selective breeding programs. Antigen-specific IgA responses were not negatively correlated with muscle depth. Our analyses indicate that selection for T. circumcincta L3 antigen-specific IgA is possible without impacting on the production traits for the Lleyn breed.

Identifikasi Genera Nematoda pada Lahan Perkebunan Karet (Hevea braziliensis) di Desa Santan Ulu Kecamatan Marangkayu Kabupaten Kutai Kartanegara

This study aims to determine the dominant nematode genus and nematode population associated with rubber plants. Field research were carried out in Santan Ulu Village, Marangkayu District, Kutai Kartanegara Regency. The laboratory works was carried out at the Laboratory of Plant Pest and Disease Sciences, Faculty of Agriculture, Mulawarman University. The study was conducted for 3 months from October to December 2017. The method in this study is a diagonal method on nine rubber trees that have produced. The obtained nematodes were identified and calculated by the population of each genus. The results showed that there are five species of nematodes in rubber plantation areas aged 5, 7 and 10 years, namely Aphelenchulus, Dorylemus, Pratylencus, Rhabditis, and Rotylenchulus. Weeds that grow on rubber plantations, namely, Imperata cylindrica L, Mikania micranta, Melastoma offine, Chromolaena odorata, and Paspalum conjungtum.

Pharmacokinetic assessment of methimazole-mediated modulation of albendazole biotransformation and efficacy in goats

To assess the hypothesis that hepatic microsomal oxidation inhibitor methimazole (MTH) could increase bioavailability of albendazole (ABZ), a study was undertaken to understand the pharmacokinetics and efficacy of ABZ in goats with and without co-adminstration of ABZ with MTH at 7.5 and 3.0 mg/kg body weight, respectively. Significant increased values (P<0.05) of time to reach concentration maximum (calculated), area under concentration-time curve (0-∞), elimination half-life (t1/2β) and total area under the first movement of plasma drug concentration time curve were observed for ABZ-SO (albendazole sulphoxide) in goats following coadministration of ABZ and MTH. Faecal egg count reduction and lower 95% confidence limit revealed resistance and susceptible for ABZ alone and co-administration of ABZ and MTH, respectively. The dominant nematode exhibiting resistance was Haemonchus spp. ED 50 for egg hatch was 0.196 indicating resistance to benzimidazole. The study suggested that coadministration of ABZ and MTH affects pharmacokinetic disposition of ABZ, which could possibly result in potentiation of anthelmintic activity of ABZ as observed through faecal egg count reduction test.

Gastrointestinal helminths of backyard chickens in selected areas of West Shoa Zone Central, Ethiopia

Gastrointestinal parasites of chickens are prevalent in many parts of the world including Ethiopia. This study was conducted with backyard chickens in Ambo, Holeta and, Dire Inchini in the West Shoa zone with the objectives of estimating the prevalence of gastrointestinal helminth infections, identifying the species present and determining associated risk factors. A cross-sectional study was conducted using 252 chickens purchased from local markets. Chickens were killed humanely and gastrointestinal tracts were examined for adult helminths. Identification of the helminths was performed using morphology and microscopy. The overall prevalence of helminth parasites in chickens was 92.1% (232/252) [95% confidence interval (CI): 88.0% - 95.1%]. 80.2% (204/252) [95% CI: 75.3% - 86.9%] and 77.8% (196/252) [95% CI: 72.1% - 82.8%] of chickens were infected with diverse nematode and cestode species, respectively. Parasitological examination revealed the presence of three nematode and five cestode species. Ascaridia galli (69.8%) and Heterakis gallinarum (13.5%) were the dominant nematode species and Railletina tetragona (54.0%) and Railletina echinobothrida (46.8%) were the most prevalent species of cestodes identified. A significant difference (p < .05) was observed between the prevalence of nematode parasites and sex, age, and origin of the chicken. Similarly, sex and origin of the chickens were significantly different with the prevalence of cestode infections. Higher prevalence was observed in male versus female chickens, in young versus adult chickens and in chickens from Holeta and Direinchin compared to Ambo. In contrast, weight, health status, diarrhea status, and age (for cestodes) were not significantly associated with nematode and cestode infection. In conclusion, the present study detected a high prevalence of diverse types of gastrointestinal helminths in backyard chickens, which could result in poor health and reduce productivity. Therefore, the present study strongly suggests appropriate and strategic control of helminthiasis to improve the health and output of backyard chickens in the study areas.

Nematode survey and biochemical characterization of Meloidogyne spp. in a main banana production area in Brazil

Brazil is the third leading banana producing country worldwide. It produces approximately 6.8 million tons in 550 thousand hectares, which represents a gross production value of 3.4 billion dollars per year. Bananas are affected by many pathogens, whereas nematodes are of main concern. Of 132 nematode species, approximately 54 are associated with the banana rhizosphere. These species are involved in the destruction of primary roots and damage to the fixation system, which results in toppling of the trees and/or reduced productivity. The main parasite species of banana trees are Radopholus similis, Helicotylenchus sp., Pratylenchus coffeae, and Meloidogyne sp. Taking into consideration the importance of banana growers in the Brazilian state of Bahia and the limited information regarding the distribution and presence of the dominant nematode species, in this study, we determined the occurrence of the main phytonematodes in banana producing regions and used isoenzyme characterization to determine the prevalent species (Meloidogyne spp). A total of 147 soil samples were collected in 36 municipalities in Bahia, representing nine regions. Approximately 65% of the samples were taken in rhizosphere areas of Prata subgroup cultivars (AAB), followed by Cavendish (22%) and Plantain (10%) cultivars, with the remainder taken from those of the Silk and Pisang Mas cultivars. Helicotylenchus multicinctus was found in 87.1% of the crops sampled, followed by Rotylenchulus reniformis in 63.3%, Meloidogyne spp. in 61.9%, Pratylenchus spp. in 2.7% and R. similis in 2.0%. Regarding the species of Meloidogyne, M. incognita was found in 41.5% of samples, followed by M. arenaria and M. javanica in 36.6% and 18.3% of the analyzed populations, respectively.

Effect of gastrointestinal nematodes on serum copper and phosphorus of growing beef calves in northwestern Argentina.

The aim of this work was to study the effect of gastrointestinal nematodes (GINs) on copper (Cu) and phosphorus (P) in blood of beef cattle in two ranches (R1 and R2) located in northwestern Argentina. In 2015-2016 (R1) and 2016-2017 (R2), in each ranch, 22 weaned female calves were divided into two groups: calves treated systematically with 200mcg/kg moxidectin every 45-50days (TG) and untreated calves (UTG). The following parameters were measured: number of fecal eggs (epg), fecal cultures, serum Cu and P levels, and live weight gain (LWG). Differences between groups were compared using analysis of variance and Tukey test. GIN infections in both ranches were subclinical and moderate, showing the highest epg (R1 = 907 ± 754; R2 = 1049 ± 1040) by mid-winter. Epg values of TG groups were always negligible (> 93% of moxidectin efficacy). The dominant nematode genera were Cooperia and Haemonchus. The average serum Cu values (μg/dl) indicated low (R1 = 49.7 ± 18) and severe (R2 = 27.2 ± 14) deficiency. The effect of treatments was evident in both ranches from late winter, with TG showing significantly (p < 0.01) higher serum levels in winter, spring, and early autumn (R1 = 65.1, 50.9, and 60.3; R2 = 48.0, 25.7, and 22.4) than UTG (R1 = 44.3, 33.9, and 32.9; R2 = 25.5, 18.2, and 16.4). There were no differences in serum P levels between groups. LWG of TG increased significantly (p < 0.008) (27.2% in R1 and 38.6% in R2), with respect to those of UTG. This study showed a negative effect of GIN on serum Cu values in moderately infected growing calves.

RELATIONSHIP OF FREE - LINGVING NEMATODE COMMUNITIES TO SOME ENVIRONMENTAL CHARACTERISTICS IN THE ORGANIC SHRIMP FARMS, CA MAU PROVINCE

Nematode communities (NC) in Tam Giang’s organic shrimp farms ponds (TGOSFP), Nam Can district, Ca Mau province were investigated in three seasons (March - dry, July - transfer and November - wet season) of 2015. Our findings underlined that the NC were expressed by high density and diversity. In addition, the environmental characteristics in TGOSFP may also be not quite optimal for shrimp farming because of high percentage of TN, TOC, low pH and anaerobic condition in sediment. The results of CCA analysis showed that main environmental parameters, such as TN, TOC, depth, DO, salinity and pH almost completely governed the abundances of several dominant gennera, things like Desmodora, Sabatieria, Terschellingia, Dichromadora, Pomponema, Halalaimus, Ptycholaimellus and Sphaerotheristus. Subsequently, the results of Pearson correlation confirmed that the abundances of genus Sabatieria, Terschellingia were significantly positive correlated with TOC, TN and depth. In contrast, genera like the Desmodora, Halalaimus and Ptycholaimellus had negative correlations with organic enrichment (TOC and TN). Additionally, almost genera were positively correlated with salinity. Analysis of the dominant nematode genera in combination with maturity index (MI) value are able to determine the ecological quality status of sediment (EcoQ) in TGOSFP. Results showed that moderate and poor EcoQ in most of TGOSFP throughtout the dry - trans - wet season. The attribute of NC and their correspondence with environmental characteristics can be considered as a good tool for environmental monitoring.

Survey of parasitic contamination of sewage sludges in northern Iran

The use of sewage sludge as fertilizer in agriculture is a convenient and economic solution, but it is essential to monitor presence of parasitic contamination. This study investigated parasites in sewage sludge of wastewater treatment plant in Gorgan, Iran. This descriptive-analytical study was performed on 18 sewage sludge samples collected from wastewater treatment plant of Gorgan within 6 months with three repeatitions per month. The samples were analyzed in the laboratory of School of Public Health at Golestan University of Medical Sciences. Analysis of parasites was done using Bailenger method of counting parasites in chamber of McMaster slides with volume of 0.3 ml. The results showed that majority of parasite eggs in the sewage sludge was related to nematodes. The dominant nematode eggs detected were related to Ancylostoma duodenale, Necator americanus and Enterobious vermicolaris. However, no parasite was found in dried sewage sludge. Considering the amount of parasite eggs in the returned sludge, it is necessary to modify the treatment process. However, it is permissible to use dried sewage sludge as agricultural fertilizer.Keywords: Parasite eggs, Protozoa, Sewage sludge, Iran

Response of estuarine meiofauna communities to shifts in spatial distribution of keystone species: An experimental approach

Current climate change directly affects species distribution by altering their physical environment and indirectly by altering interspecific interactions. The geographical distribution of fiddler crabs, keystone species of intertidal estuarine sediments, is supposed to expand poleward as a response to climate change. We experimentally investigate whether the introduction of a new species of fiddler crabs, where another different species already occurs, may affect the structural and functional composition of meiobenthic communities in intertidal areas. In order to disentangle the effect of abundance from species identity, we set up two indoor experiments (substitutive and a partial additive design) manipulating the diversity and density of two keystone species, Leptuca uruguayensis and L. leptodactyla. The results showed that the increase of the diversity keystone species did not impact any measured descriptors of nematode assemblages. By contrast, high density of keystone species, independent of the species, strongly affected the meiofauna total density, and the density of numerically dominant nematode genera. The results did not reveal any functional change in the meiofauna. Our experiments, designed to mimic the indirect effects of range expansion showed that while increasing diversity of functionally redundant keystone species had no effect on preys, increasing density negatively affected the structure of intertidal habitats.

Epidemiology and effect of gastrointestinal nematodes on beef cattle from tropical Argentina

The aim of this work was to study the epidemiology and the harmful effect of gastrointestinal nematodes (GINs) on beef cattle in the piedmont forest and grassland region of northwestern Argentina, between March 2015 and March 2016. Sixty weaned female calves were divided into three groups: STG-calves treated systematically with 200mcg/kg moxidectin every 40-50days; LTG-calves treated as usually locally implemented, with 200mcg/kg ivermectin on May 4 and August 5; and UTG-calves not receiving treatment. Moreover, a group of 20 untreated first-calving cows was monitored. Eggs per gram of faeces (epg) and faeces cultures were performed. Live weight gain (LWG) was recorded. Differences among groups were compared using analysis of variance and Tukey test. At the start of the experiment, mean epg was from moderate to high (595 ± 480); therefore, this group was treated in May. Mean UTG epg peaked (907 ± 754) in mid-winter, decreasing toward spring. LTG epg only decreased partially after treatment, showing 54.2% of ivermectin efficacy. Epg values of STG were always negligible values (95.8% of moxidectin efficacy). The dominant nematode genus was Cooperia (81.9%), followed by Haemonchus (15.5%). The effect of treatments was evident from middle autumn, with STG showing a significantly (p < 0.002) higher LWG than the other groups. Toward the end of the trial, LWG of STG and LTG increased by 27.2 and 8.2%, respectively, to those of UTG. This preliminary study showed a winter epg peak and a negative effect of GINs on LWG, even in moderately infected calves.

Effect of short-term hypoxia on the feeding activity of abundant nematode genera from an intertidal mudflat

The effect of short-term hypoxia (6 days) on the feeding activity of abundant nematode genera was investigated by means of a tracer experiment. Nematodes were sampled from the Paulina intertidal flat in the Westerschelde estuary (south-west Netherlands) and incubated with 13C pre-labelled diatoms at the sediment-water interface in oxic and hypoxic treatments. In general, specific uptake and uptake of carbon per unit of nematode carbon were low in all studied genera, which indicated that the added diatoms represented a limited food source for the investigated nematode genera. Results from such a low uptake are difficult to interpret; however, there was no significant decrease in feeding activity of all dominant nematodes in the hypoxic treatments. The low carbon uptake might be related to low access of nematodes and their low feeding preference to the added diatoms in the experimental cores.

Macrofaunal nematodes of the deep Whittard Canyon (NE Atlantic): assemblage characteristics and comparison with polychaetes

AbstractLarge nematodes form an important component of deep‐sea macrofaunal assemblages, but are often considered to be part of the meiobenthos and are rarely studied. We analysed the standing stocks, diversity, and functional group and genus‐level composition of macrofaunal nematodes at lower bathyal depths (3,500 m water depth) in the Whittard Canyon system (NE Atlantic) and on the adjacent continental slope. Five replicate sample sets were obtained using a Megacorer, at four locations (three canyon branches, one slope). Sediment samples were processed on a 500‐μm mesh to provide both nematode and polychaete data from the same samples. The dominant nematode genera included Paramesacanthion, Metacylicolaimus, Cylicolaimus and Phanodermopsis. Nematode standing stocks (density and biomass) increased significantly from slope to canyon locations. Similarly, nematode dominance increased substantially (and diversity decreased) from slope to canyon locations. Nematode feeding groups and tail shape groups also appeared to exhibit common trends across study locations. Nematode genus‐level faunal composition varied significantly between slope and canyon locations. We describe and discuss the broadly similar trends detected in the matching polychaete data, noting some differences in the polychaete density and diversity responses. We suggest that the similar trends in macrofaunal nematode and polychaete ecology across our four study locations reflect responses to both changing sedimentology and food availability.

Effects of various bivalves on meiobenthic and nematode assemblages in shallow sandy sediments

A laboratory microcosm experiment was performed to study the effect of bivalves on meiobenthic and nematode community structures. Three bivalve species dominant in shallow coastal sediments of the southern Baltic Sea differing in terms of feeding mode, faecal deposition and sediment depth penetration (Macoma balthica, Cerastoderma glaucum and Mya arenaria) were selected as model organisms: our experiment demonstrated that although the bivalves had no overall effect on total meiobenthic densities, they variously affected a number of meiobenthic major taxa. Species buried under the sediment surface (M. balthica, M. arenaria) facilitated meiobenthos to penetrate deeper sediment layers compared to the surface-dwelling bivalves (C. glaucum). The most conspicuous response of meiobenthos and nematodes to bivalve activities was, however, observed at the sediment surface: densities of juvenile bivalves and rotifers, and the dominant nematode species (Adoncholaimus thalassophygas, Desmolaimus cf. zeelandicus and Halomonhystera disjuncta) were significantly reduced in surface sediments in Macoma microcosms compared to other treatments. It is suggested that different bivalve feeding modes (deposit-feeding vs. suspension-feeding), attributes of faecal deposition (to the sediment surface vs. to subsurface sediments) and depth of sediment penetration can significantly change meiobenthic and nematode communities in sandy sediments.

Bottom-up control of fertilization on soil nematode communities differs between crop management regimes

We evaluated how fertilization impacted nematode trophic groups via changes in trophic resources (soil microbes, plant roots) and the soil environment in a 3-year fertilization experiment in a double-cropped paddy rice and upland wheat agroecosystem. Fertilization exerted a strong influence on bacterial- and fungal-feeding nematodes by changing soil microbes and the soil environment in both phases, whereas plant- and root-associated fungal-feeding nematodes were bottom-up controlled by plant roots in the upland wheat phase only. Also, fertilization-induced linkages between bacteria phyla and bacterial-feeding nematode genera were inconsistent across crop phases. Although fertilization results in bottom-up control of nematode feeding groups in well-drained soils, our findings suggest environmental filtering due to water management and crop species can be responsible for the abundance of dominant nematode genera.