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Three new species of the Microlaimus genus (Nematoda: Microlaimidae) are described from sample sediments collected in the South Atlantic, along the Continental Shelf break of Northeastern Brazil. Microlaimus paraundulatus sp. n. possesses four setiform cephalic sensillae, a buccal cavity with three small teeth, arched and slender spicules and a wave-shaped gubernaculum. Microlaimus modestus sp. n. is characterized by four small cephalic sensillae, a buccal cavity with three teeth (one large dorsal tooth), cephalated spicules and a strongly arched gubernaculum in the distal region. Microlaimus nordestinus sp. n. is characterized by the following set of features: relatively long body, eight rows of hypodermal glands that extend longitudinally along the body and a funnel-shaped gubernaculum surrounding the spicules at the distal end. An amendment of the diagnosis is proposed for the genus. [ABSTRACT FROM AUTHOR]

Three new species of the Microlaimus genus (Nematoda: Microlaimidae) are described from sample sediments collected in the South Atlantic, along the Continental Shelf break of Northeastern Brazil. Microlaimus paraundulatus sp. n. possesses four setiform cephalic sensillae, a buccal cavity with three small teeth, arched and slender spicules and a wave-shaped gubernaculum. Microlaimus modestus sp. n. is characterized by four small cephalic sensillae, a buccal cavity with three teeth (one large dorsal tooth), cephalated spicules and a strongly arched gubernaculum in the distal region. Microlaimus nordestinus sp. n. is characterized by the following set of features: relatively long body, eight rows of hypodermal glands that extend longitudinally along the body and a funnel-shaped gubernaculum surrounding the spicules at the distal end. An amendment of the diagnosis is proposed for the genus.

Fish products in Slovakia have been heavily infected with Anisakis spp. larvae, which causes human anisakiasis. We found larvae in all tested samples of frozen Atlantic herring. Anisakid allergen t-Ani s7 testing revealed 2 positive cases in humans, signaling need for health authorities to closely monitor zoonotic marine parasites, even in inland areas.

Summary: The family Oncholaimidae comprises ca 350 species of widespread nematodes. They are common in the seas and oceans and are also found in freshwater lakes and rivers. Here we provide the first description of Metoncholaimus species from the South China Sea. Metoncholaimus placatus sp. n. is characterised by the spicules 2.2-2.8 anal body diam. long, gubernaculum small, nearly parallel to the spicules, S-curved. Supplementary organ is composed of transversely elongated prominence with two sensillar structures (receptors). A pictorial key to the species level of Metoncholaimus species is provided. In this study, the D2-D3 domain of the LSU rDNA and the nearly full-length SSU rDNA were selected as targets for species identification. Phylogenetic relationships within the family Oncholaimidae remained unresolved despite of the various sequences analysed in different loci. [ABSTRACT FROM AUTHOR]

Nematodes represent the most abundant benthic metazoan of all seas and oceans, and their relative importance increases with increasing water depth. Understanding the biodiversity patterns of this dominant phylum could be a critical step towards our comprehension of the evolutionary patterns across the largest biome of the biosphere. For instance, it has been assumed for a long time that nematodes are ubiquitous across depths, latitudes and biogeographic regions, but there is still little scientific evidence for this lack of endemism. The present study is based on a meta-analysis of nematode biodiversity data collected from 246 deep-sea sites of the Atlantic Ocean and Mediterranean Sea. We explored the cosmopolitanism, rareness and potential endemism of nematode genera in deep-sea sediments. The results of this analysis indicate that only one-third of nematode families are widely distributed and could potentially be cosmopolitan, whereas 94% of the nematode genera are linked to specific habitats or bathymetric ranges. Singleton nematode genera (i.e. genera presenting as a single individual only in one specific habitat) increased in importance with increasing water depth. We conclude that rareness and endemism may be a far more common feature than previously thought in deep-sea nematode assemblages and hypothesise that the deep ocean interior could be a huge reservoir of endemic nematode species.

Wastewater treatment plants (WWTPs) represent major point sources of pollution in coastal systems, affecting benthic ecosystems. In the present study, we assessed the potential role that WWTPs have in shaping nematode communities and established baseline knowledge of free-living nematode community structures in St. Andrew Bay, Florida. Sediment samples were collected from four sites representing areas of WWTP outflow and areas with no apparent outflow, during the winter and summer. Nematode communities across sites were significantly different, and the differences were strongly associated with the distance to the nearest WWTP. While the communities were not different along transects at each site, nor across seasons, community dissimilarity across sites was high, implying strong contrasts throughout the bay system. Dominance of tolerant, opportunistic genera and Ecological Quality Status assessments suggest that the system is stressed by organic enrichment, possibly linked to the WWTPs. Our results suggest that knowledge on the life-history of dominant genera is imperative to assess the ecological quality of a benthic system, in addition to taxonomic and functional metrics. Considering the value of marine nematodes as bioindicators, more work should be done to monitor temporal variability in nematode communities in this system as future infrastructure changes alter its dynamics. [ABSTRACT FROM AUTHOR]

Cyatholaimidae is a common and diverse family of mainly marine nematodes, potentially, with a large number of species to be discovered. The taxonomy of the group is marked by a lack of information about the evolutionary history of the characters and of detailed descriptions of morphological structures that may be taxonomically relevant. Two new species of the family are described from a sublittoral region in Southeastern Brazil, emphasizing the importance of the distribution and morphology of pore complex and pore-like structures present on the cuticle. The taxonomic importance of the cuticle ornamentation and spicule shape for the Biarmifer species, as well as the precloacal supplements structures of Pomponema species, are discussed. Biarmifer nesiotes sp. nov. differs from other species of the genus by the presence of eight longitudinal rows of pore complex on the cuticle and by the shape of the copulatory structure. Pomponema longispiculum sp. nov. differs from the most similar species, P. stomachor Wieser, 1954, by the smaller number of turns of the amphidial fovea, the shorter tail and the beginning of the cuticle lateral differentiation (3/4 of the pharynx length vs. end of the pharynx, respectively). We also obtained the SSU rDNA sequence from Pomponema longispiculum sp. nov., which is closely related to Pomponema sp. (MN250093) by about 91%. Updated tabular keys to species identification of each genus (Biarmifer and Pomponema) are included, containing morphometric data, characters related to cuticle ornamentation, and copulatory structures. [ABSTRACT FROM AUTHOR]

Nematodes represent the most abundant benthic metazoan of all seas and oceans, and their relative importance increases with increasing water depth. Understanding the biodiversity patterns of this dominant phylum could be a critical step towards our comprehension of the evolutionary patterns across the largest biome of the biosphere. For instance, it has been assumed for a long time that nematodes are ubiquitous across depths, latitudes and biogeographic regions, but there is still little scientific evidence for this lack of endemism. The present study is based on a meta-analysis of nematode biodiversity data collected from 246 deep-sea sites of the Atlantic Ocean and Mediterranean Sea. We explored the cosmopolitanism, rareness and potential endemism of nematode genera in deep-sea sediments. The results of this analysis indicate that only one-third of nematode families are widely distributed and could potentially be cosmopolitan, whereas 94% of the nematode genera are linked to specific habitats or bathymetric ranges. Singleton nematode genera (i.e. genera presenting as a single individual only in one specific habitat) increased in importance with increasing water depth. We conclude that rareness and endemism may be a far more common feature than previously thought in deep-sea nematode assemblages and hypothesise that the deep ocean interior could be a huge reservoir of endemic nematode species. [ABSTRACT FROM AUTHOR]

Cyatholaimidae is a common and diverse family of mainly marine nematodes, potentially, with a large number of species to be discovered. The taxonomy of the group is marked by a lack of information about the evolutionary history of the characters and of detailed descriptions of morphological structures that may be taxonomically relevant. Two new species of the family are described from a sublittoral region in Southeastern Brazil, emphasizing the importance of the distribution and morphology of pore complex and pore-like structures present on the cuticle. The taxonomic importance of the cuticle ornamentation and spicule shape for the Biarmifer species, as well as the precloacal supplements structures of Pomponema species, are discussed. Biarmifer nesiotes sp. nov. differs from other species of the genus by the presence of eight longitudinal rows of pore complex on the cuticle and by the shape of the copulatory structure. Pomponema longispiculum sp. nov. differs from the most similar species, P. stomachor Wieser, 1954, by the smaller number of turns of the amphidial fovea, the shorter tail and the beginning of the cuticle lateral differentiation (3/4 of the pharynx length vs. end of the pharynx, respectively). We also obtained the SSU rDNA sequence from Pomponema longispiculum sp. nov., which is closely related to Pomponema sp. (MN250093) by about 91%. Updated tabular keys to species identification of each genus (Biarmifer and Pomponema) are included, containing morphometric data, characters related to cuticle ornamentation, and copulatory structures.

Summary: The family Haliplectidae is reported from Iran for the first time and Haliplectus iranicus sp. n., from a mangrove forest in the Persian Gulf, is described. The new species is characterised by one ventromedian supplement near to cloacal aperture and a group of three supplements, 10-15 μ m anterior to cloacal opening, absence of protuberant caudal papillae and tail sexual dimorphism. A tabular key containing morphometric data and morphological information of 26 valid Haliplectus species is presented. Near full length SSU rDNA sequences are provided for H. iranicus sp. n. Our SSU analysis strongly indicates that Haliplectus does not belong to the order Plectida as in the current classification, and confirms the monophyly of Haliplectus based upon currently available data, but phylogenetic relationships of the genus remain uncertain. In fact, the classification of Haliplectidae is considered incerta sedis within the class Chromadorea. [ABSTRACT FROM AUTHOR]

Differences in resource use or in tolerances to abiotic conditions are often invoked as potential mechanisms underlying the sympatric distribution of cryptic species. Additionally, the microbiome can provide physiological adaptations of the host to environmental conditions. We determined the intra- and interspecific variability of the microbiomes of three cryptic nematode species of the Litoditis marina species complex that co-occur, but show differences in abiotic tolerances. Roche 454 pyrosequencing of the microbial 16S rRNA gene revealed distinct bacterial communities characterized by a substantial diversity (85-513 OTUs) and many rare OTUs. The core microbiome of each species contained only very few OTUs (2-6), and four OTUs were identified as potentially generating tolerance to abiotic conditions. A controlled experiment in which nematodes from two cryptic species (Pm1 and Pm3) were fed with either an E. coli suspension or a bacterial mix was performed, and the 16S rRNA gene was sequenced using the MiSeq technology. OTU richness was 10-fold higher compared to the 454 data set and ranged between 1118 and 7864. This experiment confirmed the existence of species-specific microbiomes, a core microbiome with few OTUs, and high interindividual variability. The offered food source affected the bacterial community and illustrated different feeding behaviour between the cryptic species, with Pm3 exhibiting a higher degree of selective feeding than Pm1. Morphologically similar species belonging to the same feeding guild (bacterivores) can thus have substantial differences in their associated microbiomes and feeding strategy, which in turn may have important ramifications for biodiversity-ecosystem functioning relationships.

Three new species of Microlaimus are described from the continental shelf of the Campos Basin, southwest Atlantic, Brazil. Microlaimus campiensis sp. n. differs from all other species in the presence of two anterior testes, slender spicules with enlarged proximal ends, 7-11 pre-cloacal papilliform supplements, and females with a pair of constriction structures, one on each branch of the ovary. Microlaimus alexandri sp. n. shows sexual dimorphism in the size of the amphidial fovea, which occupies 100% of the diameter of the corresponding area in the male; the buccal cavity provided with five teeth and a slightly cuticularized cuticular ring. Microlaimus vitorius sp. n. has four longitudinal-lateral rows of glands associated with small pores, one seta and three pores small pre-cloacal, and the gubernaculum has a triangular base. An amendment to the diagnosis of the genus is proposed, where the number of teeth was modified. [ABSTRACT FROM AUTHOR]

Abstract Intragenomic rRNA variation is a critical concern for eukaryotic metabarcoding studies, due to its potentially confounding effects on species delimitation and biodiversity estimates derived from ‐Omics data. In the present study, we assessed patterns associated with 18S rRNA metabarcoding loci in marine nematodes, including characterization of intragenomic rRNA gene variants (number of variants and abundance profiles) and aspects of datasets that can obscure biological signals (e.g., amplification of nontarget DNA, ambiguous taxonomy assignments). We estimated amplicon sequence variants (ASVs) using DADA2 from an 18S rRNA metabarcoding dataset (Illumina MiSeq) generated from individual marine nematodes. Illumina data were analyzed in conjunction with nematode morphological identifications and nearly full‐length 18S reference sequences (~1,600 bp Sanger barcodes) generated for a subset of the same specimens. Our results indicated that levels of intragenomic rRNA variation appeared to vary widely across nematode taxa (irrespective of phylogenetic clades or ecological feeding groups) and that coamplification of nontarget DNA was common (relic DNA, gut contents, etc.). The DADA2 pipeline appeared to produce a biologically accurate profile of intragenomic rRNA variants in nematodes that was consistent with “Head‐Tail” patterns (of dominant vs. minor rRNA gene variants) identified in previous studies. Although intragenomic rRNA variation appears to be ubiquitous in marine nematodes, nematode identifications were highly congruent across our three methods for species delimitation (traditional morphological taxonomy, Sanger DNA barcoding, and high‐throughput metabarcoding). In spite of pervasive intragenomic variation and high copy number of rRNA genes, the most abundant ASVs in metabarcoding datasets are likely to represent true species barcodes and thus confer an accurate view of extant biodiversity. However, our findings also emphasize the importance of applying bioinformatic filtering techniques and developing well‐curated reference databases in order to better link rRNA molecules with specimen‐level data and alleviate the confounding effects of intragenomic gene variants in studies of microbial eukaryotes.

Three new species of Microlaimus are described from the continental shelf of the Campos Basin, southwest Atlantic, Brazil. Microlaimus campiensis sp. n. differs from all other species in the presence of two anterior testes, slender spicules with enlarged proximal ends, 7–11 pre-cloacal papilliform supplements, and females with a pair of constriction structures, one on each branch of the ovary. Microlaimus alexandri sp. n. shows sexual dimorphism in the size of the amphidial fovea, which occupies 100% of the diameter of the corresponding area in the male; the buccal cavity provided with five teeth and a slightly cuticularized cuticular ring. Microlaimus vitorius sp. n. has four longitudinal-lateral rows of glands associated with small pores, one seta and three pores small pre-cloacal, and the gubernaculum has a triangular base. An amendment to the diagnosis of the genus is proposed, where the number of teeth was modified.

Piipironus grandis gen. et sp. nov. is described from Piip submarine volcano, the Bering Sea. Piipironus gen. nov. shows all main characters of Thalassironinae but differs from all known ironids in the form of the amphid (spiral vs pocket-like) and the simultaneous presence of precloacal papilliform supplements and tubular postcloacal organs. Pared tubular postcloacal organs have never been described before for the family Ironidae. The combination of papilliform precloacal supplements and the pair of tubular postcloacal organs described for Piipironus grandis gen. et sp. nov. is unique among nematodes. The study of the nematofauna of the Piip submarine volcano began quite recently, and Piipironus is the second new genus of nematodes described from here from one sample of bottom sediments. This can be taken as one of the examples of the hyper-high diversity of marine nematodes.

Piipironus grandis gen. et sp. nov. is described from Piip submarine volcano, the Bering Sea. Piipironus gen. nov. shows all main characters of Thalassironinae but differs from all known ironids in the form of the amphid (spiral vs pocket-like) and the simultaneous presence of precloacal papilliform supplements and tubular postcloacal organs. Pared tubular postcloacal organs have never been described before for the family Ironidae. The combination of papilliform precloacal supplements and the pair of tubular postcloacal organs described for Piipironus grandis gen. et sp. nov. is unique among nematodes. The study of the nematofauna of the Piip submarine volcano began quite recently, and Piipironus is the second new genus of nematodes described from here from one sample of bottom sediments. This can be taken as one of the examples of the hyper-high diversity of marine nematodes. [ABSTRACT FROM AUTHOR]

This paper reports on the genus Cobbionema Filipjev, 1922 in Sweden with the description of four species and a revision of the genus. Cobbionema acrocerca Filipjev, 1922 is relatively small in size, with a tail that has a conical proximal and a digitate distal section. Cobbionema cylindrolaimoides Schuurmans Stekhoven, 1950 is similar to C. acrocerca in most characters except having a larger body size and heavily cuticularized mandibles. Cobbionema brevispicula sp. nov. is characterised by short spicules and a conoid tail. Cobbionema acuminata sp. nov. is characterised by a long two-part spicule, a conical tail and three (one mid dorsal and two ventrosublateral) sharply pointed tines in the anterior chamber of the stoma that are located more anterior than in all the other species. We also present a molecular phylogeny of the family based on the nearly full-length 18S and the D2-D3 expansion segment of the 28S rRNA genes. Maximum Likelihood and Bayesian trees inferred from both genes strongly support a clade that included Cobbionema, Demonema Cobb, 1894 and Halichoanolaimus de Man, 1888 and another clade with Gammanema Cobb, 1920 and Latronema Wieser, 1954 nested together. None of the trees supported the monophyly of the subfamilies Choniolaiminae and Selachinematinae.

Summary: Members of the family Leptolaimidae are reported for the first time from Iran with description of two new species of Leptolaimus from the Persian Gulf in the south of the country. Leptolaimus hormozganensis sp. n. is described based upon three populations. It differs from other Leptolaimus species in the position of the pharyngeal supplement and the number of precloacal tubular supplements and has a single sickle-shaped tubular pharyngeal supplement at mid-pharynx level in both sexes, 9-12 male precloacal supplements and one female preanal supplement. Leptolaimus dimorphus sp. n. is characterised by the presence of a pharyngeal tubular supplement only in some adults, one female preanal supplement and four male precloacal supplements. It differs from other species in that the pharyngeal supplement is only present in some specimens, presence of four male precloacal supplements, tail 50-59 μ m long and ventrosublateral position of vulva on either the right or left side of the body. Near full length SSU rDNA sequences are provided for L. hormozganensis sp. n. and two different males (one with, and one without, a pharyngeal supplement) of L. dimorphus sp. n. COI sequences for three populations of L. hormozganensis sp. n. from different regions of the Persian Gulf are also obtained. New sequences of two Leptolaimus species formed a clade with other sequenced Leptolaimus spp. and representatives of two genera of Leptolaimidae, i.e. , Aphanolaimus and Paraplectonema in a phylogeny based on SSU rDNA gene with 1.00/81 Bayesian posterior probability/maximum likelihood bootstrap (BPP/BS) values. Molecular phylogeny confirmed the synonymy of Leptolaimus and Halaphanolaimus that was formerly proposed based only on morphology. Based on SSU sequences and morphological characters, the presence of a pharyngeal supplement may not be a species-specific character and should not be used to differentiate genera. [ABSTRACT FROM AUTHOR]

The high local-scale species diversity of marine meiofauna, and of nematodes in particular, has puzzled ecologists for decades. Both pronounced niche differentiation and neutral dynamics have been suggested as mechanisms underlying that high diversity. Differential resource use is the most plausible basis for niche differentiation, yet the vast majority of studies demonstrating that this is prominent in marine nematodes are based on laboratory experiments on single species or highly simplified assemblages. Only a small number of studies have investigated resource differentiation under natural conditions. Here we use natural stable-isotope ratios of carbon and nitrogen, as well as fatty-acid profiles, to assess differential resource use and trophic structure in nine abundant estuarine tidal flat nematode species, comprising different presumed feeding modes (deposit feeders, epistratum feeders, predators) and resource guilds (herbivores, carnivores) based on buccal cavity morphology. Nematodes comprise up to three different trophic levels (from primary to tertiary consumers), yet with the exception of some herbivores, omnivory is prominent. Bivariate isotopic niche spaces were of similar size among most species, irrespective of their trophic level. Herbivory not only contributed importantly to the nutrition of suspected herbivores, but also to that of species that were previously considered carnivores based on the morphology of their buccal cavity. Herbivory mainly targets diatoms in some nematode species, yet includes dinoflagellates in others. Bacteria, in contrast, appear to be of limited nutritional importance. Odontophora setosus is identified as a predator/omnivore (possibly of heterotrophic protists) with a trophic level in between that of secondary and tertiary consumers. Our study thus demonstrates that resource differentiation is pronounced among as well as within nematode feeding modes and resource guilds. However, this study included only the most abundant species of the in situ community, hence it remains to be established whether and to what extent its conclusions can be extrapolated to entire, often highly species-rich communities. [ABSTRACT FROM AUTHOR]

Seagrass meadows are hot spots of biodiversity and play a key role in the provisioning of ecosystem goods and services but are often subjected to a regression due to a combination of multiple anthropogenic and climate-induced impacts. The ecological restoration of these habitat-forming species is a priority to reverse biodiversity loss and for the recovery of key ecosystem functions. Here we investigated the effects of seagrass (Cymodocea nodosa) restoration action on benthic biodiversity recovery assessed by a time-series analysis carried out for one year. We used nematode assemblages, the most widespread metazoan on global sediments, as a proxy of benthic biodiversity and compared the species richness, expected species number (ES51) and composition in donor and in restored seagrasses and in the adjacent unvegetated sediments. One year after the intervention, nematode biodiversity in restored seagrasses was more similar to that of the donor site than in unvegetated sediments, suggesting a progressive recovery. Overall, the nematode biodiversity of the restored seagrasses resulted in an intermediate level between unvegetated and pristine seagrass meadows, providing evidence that restoration intervention contributed to biodiversity recovery. Pristine and restored seagrass meadows hosted a high number of exclusive species, which resulted in an increase in the overall biodiversity in the investigated location. Our results indicate that the restoration of seagrass meadows has positive effects on benthic biodiversity and contributes to enhance the local biodiversity. • Nematode biodiversity in restored seagrasses recovers to values similar to the donor sites. • Pristine and restored seagrass meadows host a high number of exclusive species. • Seagrass restoration promotes high levels of benthic biodiversity. • Pristine and restored seagrasses enhance the local biodiversity of the coastal area. [ABSTRACT FROM AUTHOR]

Cold seeps provide high environmental heterogeneity for marine benthos. Site F is one of the active cold seeps in the South China Sea. In this study, free-living marine nematode communities were investigated at Site F and the adjacent deep-sea area. A total of 67 genera and 32 families were identified. The mean density at cold seep sites ranged from 13.6 to 181.8 ind./10 cm2, and that at the adjacent deep-sea sites ranged from 36.9 to 301.4 ind./10 cm2. At cold seep sites, the most dominant nematode genera were Desmoscolex , Pierrickia , Sabatieria , Halalaimus , and Dorylaimopsis while at deep-sea sites, the most dominant genera were Retrotheristus , Thalassomonhystera , Desmoscolex , Cobbia , and Halalaimus. Deposit feeders of nematodes were dominant at all sites. Results of biological trait analysis showed that there was high environmental heterogeneity for nematodes at Site F. Water depth, sediment organic matter content, and sand proportion had important influences on nematode communities. • The deep-sea nematode Desmoscolex was found abundantly at the cold seep site. • Biological trait analysis showed high environmental heterogeneity at this site. • Water depth and sediment characteristics had significant effects on nematodes. • Organic matter caused changes in nematode diversity and functional differentiation. [ABSTRACT FROM AUTHOR]

This study presents patterns of spatial and temporal variation in the meiofaunal community and nematode associations on the volcanic sandy beaches of Trindade Island, a remote oceanic island in the South-east Atlantic Ocean. Samples were collected in August (rainy season) and December 2014 (dry season) on four beaches (Tartarugas, Parcel, Cabritos and Portugueses) at three zones of the intertidal (high, mid and low). A total of 10 meiofaunal groups were found. Copepods (31%) and nematodes (27%) dominated the meiofauna in all beaches and zones, regardless of the season. Nematodes were comprised mainly of non-selective deposit feeders, with a total of 27 genera from 12 families, with Cyatholaimidae, Xyalidae and Oncholaimidae as the most diverse and abundant. Significant differences were found in the meiofaunal community, as well as in nematode associations, among seasons and intertidal zones but not among beaches. The sediment characteristics were the main drivers regulating the structure of meiobenthic fauna in Trindade Island. Our findings are also compared to other studies focusing on the meiofauna and nematodes of oceanic islands with carbonate and volcanic sediments; the major patterns are herein presented. [ABSTRACT FROM AUTHOR]

Abstract Little is known about the diet and feeding strategies of deep-sea nematodes. In this study, we investigated the trophic ecology of several macrobenthic nematode species in the abyssal zone of the Sea of Okhotsk and adjacent northwest Pacific by means of stable isotope and fatty acid analyses. A wide range of δ13C and δ15N values was found, with δ13C values ranging from −37.8 to −16.4‰ and δ15N values ranging from 5.7 to 19.2‰. The fatty acid composition of the nematode species demonstrated high variation. Planktonic FAs were found in high abundance in the nematodes at all stations, with values ranging from 31% to 34% (Metoncholaimus sp.) to 59% (Synonchinae gen. sp.). The abundance of bacterial FAs ranged from 13% to 22%. The isotopic and FA signatures exhibited a wide range of food sources in the nematode diet and highlighted the importance of sediment bacteria in the diet. The depleted isotopic signatures coupled with the increased abundance of bacterial FAs suggest that chemosynthetically derived organic matter can be an important carbon source for macrobenthic nematodes in the Kuril Basin. [ABSTRACT FROM AUTHOR]

Abstract: Studies of host‐associated microbes are critical for advancing our understanding of ecology and evolution across diverse taxa and ecosystems. Nematode worms are ubiquitous across most habitats on earth, yet little is known about host‐associated microbial assemblages within the phylum. Free‐living nematodes are globally abundant and diverse in marine sediments, with species exhibiting distinct buccal cavity (mouth) morphologies that are thought to play an important role in feeding ecology and life history strategies. Here, we investigated patterns in marine nematode microbiomes, by characterizing host‐associated microbial taxa in 281 worms isolated from a range of habitat types (deep‐sea, shallow water, methane seeps, Lophelia coral mounds, kelp holdfasts) across three distinct geographic regions (Arctic, Southern California and Gulf of Mexico). Microbiome profiles were generated from single worms spanning 33 distinct morphological genera, using a two‐gene metabarcoding approach to amplify the V4 region of the 16S ribosomal RNA (rRNA) gene targeting bacteria/archaea and the V1–V2 region of the 18S rRNA gene targeting microbial eukaryotes. Contrary to our expectations, nematode microbiome profiles demonstrated no distinct patterns either globally (across depths and ocean basins) or locally (within site); prokaryotic and eukaryotic microbial assemblages did not correlate with nematode feeding morphology, host phylogeny or morphological identity, ocean region or marine habitat type. However, fine‐scale analysis of nematode microbiomes revealed a variety of novel ecological interactions, including putative parasites and symbionts, and potential associations with bacterial/archaeal taxa involved in nitrogen and methane cycling. Our results suggest that in marine habitats, free‐living nematodes may utilize diverse and generalist foraging strategies that are not correlated with host genotype or feeding morphology. Furthermore, some abiotic factors such as geographic region and habitat type do not appear to play an obvious role in structuring host–microbe associations or feeding preferences. [ABSTRACT FROM AUTHOR]

The present study describes the nematode assemblage of the bay of Tamandaré (Brazil), a tropical sandy beach, during the low, flood, high and ebb tides of two consecutive tidal cycles in four different months of the year (May, July, September and November). The nematode assemblage was dominated by Metachromadora and Perepsilonema and varied significantly between months and tides. Densities were lower in July, and changes in assemblage structure occurred during the transitional periods between rainy and dry months, which showed the influence of rainfall. Flood and ebb tides appeared to exercise the greatest influences over the tidal cycle, although the patterns were not very clear. Identification at genera/species level is recommended for future studies, to better understand the patterns of nematode assemblages during tidal cycles.

Marine nematodes play a vital role in the ecosystem of seas and estuaries as a diverse species, universally rich and often showing sensitive responses to ecological changes. During present study, surveys were conducted at four locations of Sindh coast viz., Kaemari, Korangi Creek, Ibrahim Haidry, Mubarak Village and two of Balochistan coast viz., Gadani and Sonmiani beach. As a result, four new species Oncholaimus paraoxyuris n. sp., Metoncholaimus medispiculatum n. sp., Theristus (P) karachiense n. sp. and Theristus cylindricus n. sp. were found. O. paraoxyuris, M. medispiculatum and T. karachiense were molecularly identified on the basis of 18S ribosomal gene with accession numbers KY497017, KY979964 and KY979968, respectively. [ABSTRACT FROM AUTHOR]

Investigations into nematode density and species assemblages have been conducted in different types of mangroves worldwide, but these studies have typically been limited to one type of plant or tree species. The invasive salt marsh grass Spartina alterniflora has successively invaded native mangroves along the southern coasts of China during the preceding two decades. However, few meiofauna studies on the impacts of S. alterniflora have been conducted, and the consequences of this invasion on ecosystem composition and function remain unclear. The hypothesis of this study was that the spatial and seasonal distribution of nematode assemblages vary significantly among three native mangrove habitats ( Kandelia obovata, Aegiceras corniculatum, and Avicennia marina) and between these habitats and a fourth habitat that was colonized by S. alterniflora, in Zhangjiang Estuary, China. Our results demonstrated that different species dominated in different habitats seasonally. Highly significant differences in density, number of species, diversity index, and maturity index were present among the four habitats. ANOSIM results revealed that there were significant differences in nematode assemblages among the four habitats and seasons, with the S. alterniflora habitat exhibiting the lowest mean values of number of species, Shannon-Wiener diversity index, richness index, and maturity index in the four seasons. This suggests that the presence of S. alterniflora disrupted nematode assemblages. [ABSTRACT FROM AUTHOR]

We investigated genetic diversity and population genetic structure of two common benthic nematode species, Ptycholaimellus pandispiculatus and Terschellingia longicaudata, from sandy beaches in the area of Bandar Abbas (Iran), Persian Gulf. Based upon partial mitochondrial cytochrome oxidase c subunit 1 ( COI) gene data, 17 and two haplotypes were found for P. pandispiculatus and Te. longicaudata, respectively. Analysis of molecular variance did not reveal a significant population genetic structure for either species. The absence of genetic structuring indicates substantial dispersal and gene flow in our study area. To assess the species structure of Te. longicaudata at a larger geographic scale, we compared 18S rDNA and COI sequences from Iran and the Scheldt Estuary in The Netherlands to ascertain whether they truly belong to the same species. Our data confirmed previous studies that Te. longicaudata likely constitutes a complex of multiple cryptic species, with one of these species having a (near) cosmopolitan distribution. [ABSTRACT FROM AUTHOR]

The population structure (males, females and juveniles) and density of Mesacanthion hirsutum Gerlach were studied during the tides (low, flood, high and ebb) of two consecutive tidal cycles in four different months of the year (May, July, September and November). Mesacanthion hirsutum density variations showed association with the rainfall cycle, with lower densities during July and September and significantly higher values in May and November. The population structure was constituted mostly by juveniles indicating a continuous reproduction during all the studied period. There were no significant differences between light and dark periods of the day, however, the higher densities detected during the high and ebb tidal stages demonstrate that this species could be dispersing through the water column and/or migrating within the sediment.A estrutura populacional (machos, fêmeas e juvenis) e densidade de Mesacanthion hirsutum Gerlach foram estudadas durante as marés (baixa, enchente, alta e vazante) de dois ciclos de maré consecutivos, em quatro meses diferentes do ano (Maio, Julho, Setembro e Novembro). As variações de densidade de Mesacanthion hirsutum mostraram associação com o ciclo de chuvas, com densidades mais baixas durante Julho e Setembro e significativamente maiores em Maio e Novembro. A estrutura populacional constituiu-se em sua maior parte por juvenis indicando uma reprodução continua durante todo o período de estudo. Não foram encontradas diferenças significativas entre os períodos claros e escuros do dia, contudo maiores densidades foram detectadas durante as marés altas e vazantes demonstrando que a espécie pode estar se dispersando através da coluna d'água e/ou migrando dentro do sedimento.

Daptonema oxycerca was originally described from the North Sea and, up to now, nothing is known of this species in tropical regions. The spatio-temporal distribution and the population structure of this species was studied during one-year period (from May 1998 through April 1999) in Coroa Grande, Rio de Janeiro, Brazil. For sampling, two fixed, parallel transects were established perpendicularly to the shoreline, and at each transect, four, equally spaced levels were marked to represent the upper and the low intertidal zones. The lowest temperatures occurred in the end of the austral winter and first month of the spring and the highest temperatures occurred in the austral summer. The density of D. oxycerca varied during the year, with a peak in August. This tendency was observed for males, ovigerous females, and non-ovigerous females. The species density was negative correlated with temperature. The sex ratio was not statistically significant. D. oxycerca was most abundant at the upper intertidal level in both transects. This work provides the first record of D. oxycerca in Brazil, and confirms the influence of temperature in regulating its population density.Daptonema oxycerca foi descrita originalmente para o Mar do Norte, mas até o momento nada se conhece sobre essa espécie em regiões tropicais. A distribuição espaço-temporal e a estrutura populacional de D. oxycerca foram estudadas durante o período de um ano (de Maio 1998 a Abril 1999) em Coroa Grande, Rio de Janeiro, Brasil. Para a amostragem, dois transectos fixos e perpendiculares à linha d'água foram estabelecidos, e, em cada transecto, quatro níveis foram marcados para representar as zonas superior e inferior do médiolitoral. As menores temperaturas foram observadas no final do inverno e início da primavera e as maiores temperaturas no verão. A densidade de D. oxycerca variou durante o ano, com um pico em agosto. Essa tendência foi observada para os machos, as fêmeas grávidas e as fêmeas não-grávidas. A densidade da espécie correlacionou-se negativamente com a temperatura. A variação da razão sexual não foi significativa. D. oxycerca foi mais abundante no nível superior do médiolitoral em ambos os transectos. Esse trabalho representa o primeiro registro de D. oxycerca no Brasil, assim como, confirma a influência da temperatura na regulação de sua densidade populacional.

Free-living marine nematodes are valuable biological indicators for different environmental disturbances. Their taxonomic composition and functional traits often respond to environmental changes. In this study, marine nematodes, collected from the Bohai sea on the northeastern coast of China in 2014, were investigated in terms of their taxonomic composition and functional traits. Furthermore, the environmental quality of the investigated area was assessed based on nematode metrics. The studied nematode community showed spatial variation in taxonomic and functional composition, in response to changes in environmental variables such as sediment chlorophyll-a, phaeophytin-a, organic matter content, silt-clay content etc. Overall, high percentage of tolerant marine nematodes species or colonizers predominated, suggesting a disturbed environmental condition of the study area. Further results from the environmental quality assessment based on nematode metrics indicated a moderate quality status at the most investigated stations. • Nematodes contributed to the indication of certain disturbed habitats. • Nematodes reflected the influence of river discharge and land-based pollution. • Tolerant species or colonizers predominated the studied nematode communities. • Most investigated stations had moderate environmental quality status. [ABSTRACT FROM AUTHOR]

Species of the marine nematode of the genus Desmodora have been found to dominate (up to 78%) in the nematode fauna from the hydrothermal vent communities of submarine Piip volcano, Bering Sea. The morphological characteristics and molecular genetic data of Desmodora specimens from different habitats of the volcano were studied and three new and one known species have been described: Desmodora hydrothermica sp.nov. , Desmodora marci, Desmodora spongiophila sp.nov., Desmodora spongiocola sp.nov. The species often lived together, but a pronounced spatial specialization was observed. Desmodora spongiophila sp.nov. and Desmodora spongiocola sp.nov. were abundant inhabitants of the vulcanellids and some hexactenellids. Desmodora hydrothermica sp.nov. dominated in microbial mats on the carbonate chimneys from the South Summit, while Desmodora marci was found on stones near vents and in bottom sediments with Calyptogena pacifica (Bivalvia: Vesicomyidae). The last two species were already known in deep-sea reduced environments of the Pacific and Atlantic oceans, in similar habitats. The δ13C and δ15N values and fatty acids composition of Desmodora samples from hydrothermal habitats confirmed the consumption of chemosynthetically derived organic matter. SSU and D2-D3 of LSU phylogenetic trees largely agree with those of previous analyses indicating that Desmodora is not monophyletic. Moreover, phylogenetic relationships within the subfamily Desmodorinae remained unresolved. [ABSTRACT FROM AUTHOR]

Stalactites (CaCO3 and salt) from water seeps are frequently encountered in ceilings of mine tunnels whenever they intersect water-bearing faults or fractures. To determine whether stalactites could be mineralized traps for indigenous fracture water microorganisms, we analyzed stalactites collected from three different mines ranging in depth from 1.3 to 3.1 km. During sampling in Beatrix gold mine (1.4 km beneath the surface), central South Africa, CaCO3 stalactites growing on the mine tunnel ceiling were collected and discovered, in two cases, to contain a living obligate brackish water/marine nematode species, Monhystrella parvella. After sterilization of the outer surface, mineral layers were physically removed from the outside to the interior, the DNA extracted. Based upon 16S and 18S rRNA gene sequencing, Archaea, Bacteria and Eukarya in different combinations were detected for each layer. . Using CT scan and electron microscopy the inner structure of CaCO3 and salt stalactites were analyzed. CaCO3 stalactites show a complex pattern of lamellae carrying bacterially precipitated mineral structures. Nematoda were clearly identified between these layers confirming that bacteria and nematodes live inside the stalactites and not only in the central straw. Salt stalactites exhibit a more uniform internal structure. Surprisingly, several Bacteria showing highest sequence identities to marine Bacteria were identified. This, together with the observation that the nematode M. parvella recovered from Beatrix gold mine stalactite can only survive in a salty environment makes the origin of the deep subsurface colonization enigmatic. The possibility of a Permian origin is discussed. Our results indicate stalactites are suitable for biodiversity recovery and act as natural traps for microorganisms in the fissure water long after the water that formed the stalactite stopped flowing.

Marine ecosystems are experiencing accelerating population and species loss. Some ecosystem functions are decreasing and there is growing interest in the link between biodiversity and ecosystem functioning. The role of cryptic (morphologically identical but genetically distinct) species in this biodiversity-ecosystem functioning link is unclear and has not yet been formally tested. We tested if there is a differential effect of four cryptic species of the bacterivorous nematode Litoditis marina on the decomposition process of macroalgae. Bacterivorous nematodes can stimulate or slow down bacterial activity and modify the bacterial assemblage composition. Moreover, we tested if interspecific interactions among the four cryptic species influence the decomposition process. A laboratory experiment with both mono- and multispecific nematode cultures was conducted, and loss of organic matter and the activity of two key extracellular enzymes for the degradation of phytodetritus were assessed. L. marina mainly influenced qualitative aspects of the decomposition process rather than its overall rate: an effect of the nematodes on the enzymatic activities became manifest, although no clear nematode effect on bulk organic matter weight loss was found. We also demonstrated that species-specific effects on the decomposition process existed. Combining the four cryptic species resulted in high competition, with one dominant species, but without complete exclusion of other species. These interspecific interactions translated into different effects on the decomposition process. The species-specific differences indicated that each cryptic species may play an important and distinct role in ecosystem functioning. Functional differences may result in coexistence among very similar species. [ABSTRACT FROM AUTHOR]

A new species of free-living marine draconematid nematode, Dracograllus trukensis sp. nov., is described based on the specimens collected from the sediments of a intertidal seagrass bed from Chuuk Islands, Micronesia. Dracograllus trukensis sp. nov. differs from other species of the genus by the combination of the following characteristics: the presence of numerous minute spiny ornamented body cuticular annules in both sexes, eight cephalic adhesion tubes inserted on the head capsule in both sexes, the presence of stiff posteriorly directed setae anterior to posterior adhesion tubes in both sexes, the shape (large, elongated, open loop-shaped in male and large, elongated, closed loop-shaped in female) and position (longer ventral arm extending to the first body annule in male) of amphideal fovea, shorter spicule length (34-42 μm), the presence of sexual dimorphism in shape and length of the non-annulated tail terminus, and number of posterior sublateral adhesion tubes (10 in male and 13-15 in female) and posterior subventral adhesion tubes (8-10 in male and 9-11 in female). A comparative table on the biogeographical and ecological characteristics of the species of Dracograllus is presented. This is the first taxonomic report on the genus Dracograllus from Chuuk Islands, Micronesia, central western Pacific Ocean. [ABSTRACT FROM AUTHOR]

Maturity index (MI), based on nematode life strategies, has been proposed in 1990 to assess the possible variations of the terrestrial and freshwater nematode assemblages induced by anthropogenic activities. It was subsequently applied also to marine ecosystems and, even if comparatively not yet very popular, it offers a good method to assess the ecological quality in relation to a wide range of anthropogenic drivers. However, few data are available on its response to physical stress, a key factor especially in the coastal areas. In this study, marine nematode genera from two study cases carried out in Maldives are used to test both MI and life strategy traits (i.e., c-p classes) for detecting the effects of physical disturbance. The results confirm that nematodes are well adapted to physical stress showing a general high rate of recovery. C-p scaling and MI did not seem to be appropriate for revealing this disturbance type probably because there are no empirical evidences on the life strategy of several genera, and a possible differential response to various disturbance types may be hypothesized. [ABSTRACT FROM AUTHOR]

The effect of short and long-term induced anoxia on a benthic nematode community and its potential for recovery after reoxygenation were investigated in an in situ experiment on a silty-sand bottom in the Gulf of Trieste, the northern Adriatic Sea. Anoxia was created artificially by three underwater benthic Plexiglas chambers at a depth of 24 m. Treatments lasted for 2, 23 and 307 days. Control samples (Normoxia) were taken on 3 (Normoxia 1) and 25 (Normoxia 2) August 2010 outside the chambers (4–5 m further). After opening the chambers, recovery cores were taken after 7 days (Anoxia 2D), 30 days (Anoxia 23D) and 90 days (Anoxia 307D). Our results revealed that short-term anoxia (Anoxia 2D) did not affect nematode total density and diversity, community structure and their vertical distribution in the sediment. However, total and vertical nematode density, species richness and diversity decreased at 23 days and decreased further at 307 days anoxia. Some nematode species like Metalinhomoeus effilatus, Paralinhomoeus caxinus and Terschellingia longicaudata even survived at 307 days anoxia treatment. Our results also demonstrated that nematode community exposed to 23 days anoxia did not recover after 30 days sediment reoxygenation but, a full recovery was observed after 90 days for nematode community exposed to 307 days anoxia. Feeding type contribution (functional aspect) of the nematode community also changed at the anoxia treatments and during the recovery process. This change was most drastic at the Anoxia 23D and 307D treatments. At both Normoxia and Anoxia 2D treatments, selective deposit feeders (1A), non-selective deposit feeders (1B) and epistrate (diatom) feeders (2A) nematodes were observed in the dominant nematode community. Epistrate feeders disappeared from in the Anoxia 23D treatment epistrate and also selective deposit feeders did not belong to the dominant nematode species in the Anoxia 307D treatment. After the recovery process, epistrate feeders and selective deposit feeding nematodes reappeared again amongst the dominant nematode species after 30 and 90 days of recovery, respectively. [ABSTRACT FROM AUTHOR]

Marine nematodes belonging to two genera Prooncholaimus and Acanthonchus are described from Tanjung Tajam on the westernmost end of Pulau Ubin in the East Johor Strait. Prooncholaimus tani new species is characterised by having short cervical setae, a large buccal cavity, pocket-shaped amphid, thin gubernaculum and curved, L-shaped spicules. Acanthonchus singaporensis new species has a cuticle striated with transverse rows of minute punctations but is irregular laterally at the posterior region; cervical setae are present posterior to the amphid, the latter being multispiral with a total of 5.5 turns. Spicules are paired, cuticulatised. The gubernaculum is also paired and almost equal length to the spicules. Six tubular supplements are present with the most anterior large and heavily cuticularised with a hook near the posterior end of the supplement. [ABSTRACT FROM AUTHOR]

Pseudelzalia longisetagen. nov, sp. nov. andParamonohystera sinicasp. nov. from subtidal sediment in the East China Sea are described.Pseudelzaliais characterized by 6 labial papillae and 10 cephalic setae, cylindrical buccal cavity, elongate (>2 anal body diameter) spicules, and conico-cylindrical tail devoid of terminal setae. It differs fromElzaliaby the absence of terminal setae.Pseudelzalia longisetasp. nov. is 647–853 μm long, has 7–8 μm long cervical setae, 11–14 μm long caudal setae, 25–41 μm long spicules about 2.1–2.7 anal diameter, and pointed tail-tip.Paramonohystera sinicapossesses 12 cephalic setae, a character found in four congeners:Paramonohysterabuetschlii(Bresslau and Schuurmans Stekhoven in Schuurmans Stekhoven, 1935,ParamonohysterapilosaBoucher, 1971,ParamonohysteraconcinnaLorenzen, 1977 andParamonohysterahalerbaFadeeva and Belogurov, 1987. It differs fromP.buetschliiby shorter body (933–1023 μm versus 2000–2200 μm); fromP.pilosaby the much shorter spicules (79–88 μm versus 167 μm) and narrower head (13–16 µm versus 32 µm); fromP.concinnaby smooth cephalic setae (versus segmented); and fromP.halerbaby the absence of two rows of setae on the ventral side of the tail (versus present). Based on the evaluation of nominal species, we recognize 14 valid species and provide an emended diagnosis and a tabular key forParamonohystera. http://www.zoobank.org/urn:lsid:zoobank.org:pub:474B8F17-AED7-4078-8176-DFC499B78526 [ABSTRACT FROM AUTHOR]

Nematodes are small multicellular, thread-like organisms, inhabiting almost all conceivable environments; among these, some 25 % are free-living marine forms with a population density of (1-12) × 10 inds m in seabed sediment, reaching maximum values in muddy estuaries and salt marshes. A large quantity of carbon from the salt marsh plants enters the ecosystem via the detritus pathway, in which nematodes play an important role through their feeding and bioturbation activities. Vegetation influences the sedimentary environment and modifies the distribution pattern of nematode communities in coastal wetlands. Nematodes are coupled closely with bacteria/detritus in microbial food webs, stimulating bacterial growth and subsequent nutrient remineralization; they provide food sources for higher trophic levels and serve as a linkage between micro- and macro-fauna. Furthermore, nematodes have a potential to provide proxies that can be used in diagnosing environmental quality. In China, only a limited number of nematode data sets are available for the coastal wetlands across several different climatic zones. It is necessary to carry out additional investigations into the biology and ecology of nematodes in order to delineate their ecological functioning in coastal wetlands. On such a basis, the contribution made by nematodes to material cycling and the ecological functioning in coastal wetlands can be quantified. The assessment of their biological diversity should be a focus, which is fundamental in the study of wetland ecosystem dynamic mechanisms. In addition to laboratory and mesocosm experiments, mathematical models should be established to predict the responses of ecosystem to the environmental disturbance. Finally, it is necessary to improve the techniques for nematode analysis, to enhance the efficiency of data acquisition. [ABSTRACT FROM AUTHOR]

The Stilbonematinae are a monophyletic group of marine nematodes that are characterized by a coat of thiotrophic bacterial symbionts. Among the ten known genera of the Stilbonematinae, the genusRobbeaGerlach1956 had a problematic taxonomic history of synonymizations and indications of polyphyletic origin. Here we describe three new species of the genus,R. hypermnestrasp. nov.,R. ruetzlerisp. nov. andR. agricolasp. nov., using conventional light microscopy, interference contrast microscopy and SEM. We provide 18S rRNA gene sequences of all three species, together with new sequences for the generaCatanemaandLeptonemella. Both our morphological analyses as well as our phylogenetic reconstructions corroborate the genusRobbea. In our phylogenetic analysis the three species of the genusRobbeaform a distinct clade in the Stilbonematinae radiation and are clearly separated from the clade of the genusCatanema, which has previously been synonymized withRobbea. Surprisingly, inR. hypermnestrasp. nov. all females are intersexes exhibiting male sexual characters. Our extended dataset of Stilbonematinae 18S rRNA genes for the first time allows the identification of the different genera, e.g. in a barcoding approach. http://zoobank.org/urn:lsid:zoobank.org:pub:D37C3F5A-CF2B-40E6-8B09-3C72EEED60B0 [ABSTRACT FROM PUBLISHER]

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In the current study we provide a reviewed list of valid genera and species of Xyalidae, a widespread family of mostly marine free-living nematodes. Comments are added about the historic background and taxonomic situation of the family, all valid genera and, when necessary, diagnostic characters are given. Additionally, information about distribution and geographical location of species recorded along the Brazilian coast is provided. Our review recognized 46 valid genera, 450 valid species and 73 descriptions without enough morphological information for identification ( species inquerendae). Nearly 80 % of the species inquerendae belong to Daptonema and Theristus. To avoid homonymies, two Daptonema species were renamed, Daptonema biwaensis (Tsalolikhin, 2002) new name (former Mongolotheristus timoshkini) and Daptonema vietnamensis (Gagarin and Thu, 2008) new name (former D. curvatum sensu Gagarin and Thu, 2008). Cenolaimus sapeloensis is transferred to Xyala sapeloensis comb. nov. Along the Brazilian coast 28 genera and 41 species have been recorded. The species Elzalia floresi, Metadesmolaimus tersus, Paramonohystera stricta, Pseudosteineria scopae, Rhynchonema cemae, R. veronicae, Steineria ericia, S. marcorum, S. pavo, S. tripartita, Theristus acribus, T. flevensis, T. macroflevensis, T. pertenuis, T. stranus, Trichotheristus heterus, T. setosus and Zygonemella striata have the Brazilian coast as the type locality. Among all species, three occurred across three geographic regions, while the large majority was restricted to one. Xyalidae is typically encountered in oceanic sandy beaches, with only the species belonging to Daptonema, Theristus, Trichotheristus and Zygonemella being recorded in estuarine sediments. This observation suggests that the colonization of inland waters occurred multiple times along the evolutionary history. [ABSTRACT FROM AUTHOR]

The responses of nematode communities to short-term hypoxia (1 and 7 days) were investigated in three North Sea stations with different sediment types (coarse silt, fine sand and medium sand). In the field, nematode density, diversity, vertical distribution and community structure differ among the stations. In the laboratory, oxic and hypoxic treatments were established for 1 and 7 days for all sediment types. Comparison between field control and oxic day 1 treatments showed that experimental sediment handling did not affect nematode characteristics. Our results revealed that short-term hypoxia did not affect total density, diversity, community composition, vertical density profiles (except in the fine sand) and densities of five dominant species in all sediment types. [ABSTRACT FROM AUTHOR]