Free-living Nematode Species Research Articles

More than 35 years of studies on marine nematodes from Tunisia: a checklist of species and their distribution.

This work provides an inventory of species of free-living nematodes from Tunisian waters, based on samples collected from September 1977 until March 2013. Sediment samples were taken from 8 ecosystems: the Lagoons of Bizerte, Ghar El Melh and Bou Ghrara, Northern and Southern Lakes of Tunis, Old Harbor of Bizerte, Bizerte Bay and Ichkeul Lake. A total of 31 families, 133 genera, and 249 species of marine nematodes are currently known from Tunisia. The Xyalidae (with 30 species), Cyatholaimidae (25), Chromadoridae and Linhomoeidae (each 21) and Comesomatidae (20) are the richest families. Among them, Daptonema (with 9 species), Pomponema and Sabatieria (with 7 each) are the most species-rich genera. Some species were recovered only from a specific type of ecosystem. In detail, 109 species were recovered from lagoons, 56 species from sandy beaches and 6 species from mudflats. The 78 remaining species were widely distributed in Tunisian waters and four of these (Terschellingia longicaudata, Oncholaimus campylocercoides, Sabatieria pulchra and Theristus flevensis) were present in most of the 8 ecosystems studied.

Two new nematode species of the genus Daptonema Cobb, 1920 (Nematoda, Xyalidae) from mangrove forest estuary of the Red River (Vietnam)

Illustrated discriptions are given of two new marine free-living nematode species of the genus Daptonema Cobb, 1920, D. paraoxyuroides sp. n. and D. balatum sp. n., found in the estuary of the Red River in North Vietnam. D. paraoxyuroides sp. n. resembles D. oxyuroides, but differs from it in its shorter and thicker body, less slender tail, shorter cephalic setae, and shorter spicules. D. balatum sp. n. differs from all known valid species of the genus Daptonema by the special structure of the copulative apparatus of males.

Two new nematode species, Linhystera breviapophysis and L. longiapophysis (Xyalidae, Nematoda), from the East China Sea

Two new species of free-living nematodes discovered from the sediments in the East China Sea are described: Linhystera breviapophysis sp. nov. and L. longiapophysis sp. nov. Both species possess a dorso-caudally directed gubernacular apophysis, which makes them distinctly different from the two already known species of Linhystera. Linhystera breviapophysis is characterized by a gubernacular apophysis about 3.3 μm long, the presence of a crown of cervical setae and a filiform tail. Linhystera longiapophysis is characterized by a prominent gubernacular apophysis about 10 μm long, sparse cervical setae and a long filiform tail. An emended diagnosis of Linhystera and a pictorial dichotomous key to the species are given.

Benthic Protozoa and Metazoa living in deep anoxic and hydrogen sulfide conditions of the Black Sea: Direct observations of actively moving Ciliophora and Nematoda

This study was conducted to search for living fauna in seafloor sediments from nearly 300 m water depth in the outflow area of the Bosporus into the Black Sea. During our investigations we identified seven higher level meiobenthic taxa in the anoxic and sulfidic sediments at 296 m water depth: Gromiida, Ciliophora, Foraminifera (soft-shelled), Nematoda, Kinorhyncha, Harpacticoida and one taxonomically unknown form. Hence, these Black Sea sediments seem to be a natural habitat for some eukaryotes. Furthermore, direct microscopic observations of alive and actively moving fauna demonstrates the presence of two species of ciliates, one species of free-living nematodes, and one unknown organism. As evidence, the activity of these organisms was recorded with a video camera. This indicates that metazoa and protozoa can live in the Black Sea under these more extreme conditions. However, the environmental factors and the specific physiological and biochemical processes used by the benthic fauna to retain metabolic activity and facilitate survival under anoxic and sulfidic conditions are still unknown. As well the distribution of benthos as a whole and of the individual taxa in other sulfidic sediments of the Black Sea needs to be investigated. Nevertheless, the presented observation of alive benthic organisms opens new perspectives to study of metazoan and protozoan life in Black Sea sediments lacking oxygen and containing sulfide.

ДВА НОВЫХ ВИДА РОДА LAIMYDORUS SIDDIQI, 1969 (NEMATODA, DORYLAIMIDA) ИЗ МЕЛКИХ ПРЕСНОВОДНЫХ ВОДОЕМОВ ВО ВЬЕТНАМЕ

Two new species of free-living nematodes of the genus Laimydorus (L. gigas sp. nov. and L. tenuis sp. nov.), found in the sediments of small freshwater bodies in Vietnam, are described and illustrated. Laimydorus gigas sp. nov. is similar to L. distinctus Dey, Baqri, 1986 and L. elephas Andrassy, 1988. From the former species it differs in the longer tail in females, the shorter spicules and greater number of supplements in males. From L. elephas it differs in the thinner cuticle, thinner body, comparatively longer odontostyle and comparatively longer prerectum in females. Laimydorus tenuis sp. nov. is similar to L. merogaster (Steiner, 1916) and L. pinguis Andrassy, 1988. From the former species it differs in the thinner cuticle, thinner body, shorter odontostyle, shorter spicules and smaller number of supplements in males. From L. pinguis it differs in the thinner body, shorter tail in females, another position of vulva and comparatively longer prerectum in females.

TheHalomonhystera disjunctapopulation is homogeneous across the Håkon Mosby mud volcano (Barents Sea) but is genetically differentiated from its shallow-water relatives

The deep sea has a high biodiversity and a characteristic bathyal fauna. Earlier evidence suggested that at least some shallow-water species invaded the ecosystem followed by radiation leading to endemic deep-sea lineages with a genetic and/or morphological similarity to their shallow-water counterparts. The nematode Halomonhystera disjuncta has been reported from shallow-water habitats and the deep sea [Håkon Mosby mud volcano (HMMV)], but the morphological features and the phylogenetic relationships between deep-sea and shallow-water representatives remain largely unknown. Furthermore, nothing is known about the genetic structure of the H. disjuncta population within the HMMV. This study is the first integrative approach in which the morphological and phylogenetic relationships between a deep-sea and shallow-water free-living nematode species are investigated. To elucidate the phylogenetic relationships, we analysed the mitochondrial gene Cytochrome oxidase c subunit I (COI) and three nuclear ribosomal genes (Internal Transcribed Spacer region, 18S and the D2D3 region of 28S). Our results show that deep-sea nematodes comprise an endemic lineage compared to the shallow-water representatives with different morphometric features. COI genetic divergence between the deep-sea and shallow-water specimens ranges between 19.1% and 25.2%. Taking these findings into account, we conclude that the deep-sea form is a new species. amova revealed no genetic structure across the HMMV, suggesting that nematodes are able to disperse efficiently in the mud volcano.

Three new species of nematodes (Nematoda: Enoplida) from coastal waters of Vietnam

Three new species of free-living nematodes of the order Enoplida from coastal shallow waters of northern Vietnam are described and illustrated. Paramesacanthion vietnamicum sp. n. is morphologically close to P. oxycephalum (Ditlevsen, 1926), P. truncum Vitiello, 1971, and P. hirsutum Warwick, 1970; however, it differs in lacking subcephalic setae and in having articulate cephalic setae in the males. Viscosia pygmaea sp. n. is morphologically similar to V. parva Kreis, 1929 but differs in having a shorter body and a shorter and thicker tail in the females. V. pygmaea is distinguished from V. megalaima (Ditlevsen, 1928) by its shorter body, longer cephalic setae, more slender tail, and the position of the vulva. Viscosia longicaudatoides sp. n. can be distinguished from V. parva and V. timmi Gagarin, Nguyen Vu Thanh, 2007 by its thinner body, longer and more slender tail, and shorter and narrower stoma. In contrast to V. timmi, it has short spicules and lacks vesicle-like cells between the gut and the longitudinal chords.

Description of two species of free-living nematodes (Nematoda) from fresh waterbodies of Vietnam

The new nematode species Monhystera longivaginata sp. n. and the rare species Mononchulus nodicaudatus (Daday, 1901) collected in waterbodies of Vietnam are described. M. longivaginata sp. n. is morphologically similar to M. paludicola de Man, 1881, but differs from it in a longer and slenderer tail in females, ocelli situated closer to the anterior end of the body, the presence of a postvulval gland cell, and a longer vagina. The genus Monhystera Bastian, 1865 is revised, and several species of this genus (M. lemani Juget, 1969, M. macramphus Filipjev, 1923, M. amabilis Gagarin, 1997, M. hamata Gagarin et Nguyen Vu Thanh, 2005, and M. melnikae Gagarin et Naumova, 2010) are transferred to the genus Eumonhystera Andrassy, 1981 as E. lemani (Juget, 1969) comb. nov., E. macramphus (Filipjev, 1929) comb. nov., E. amabilis (Gagarin, 1997) comb. nov., E. hamata (Gagarin et Nguyen Vu Thanh, 2005) comb. nov., and E. melnikae (Gagarin et Naumova, 2010) comb. nov.

Mudwigglus gen. n. (Nematoda: Diplopeltidae) from the continental slope of New Zealand, with description of three new species and notes on their distribution.

Three new free-living nematode species belonging to the genus Mudwigglus gen. n. are described from the continental slope of New Zealand. The new genus is characterised by four short cephalic setae, fovea amphidialis in the shape of an elongated loop, narrow mouth opening, small, lightly cuticularised buccal cavity, pharynx with oval-shaped basal bulb, and secretory-excretory pore (if present) at level of pharyngeal bulb or slightly anterior. Mudwigglus gen. et sp. n. differs from other genera of the family Diplopeltidae in the combination of the following traits: presence of reflexed ovaries, male reproductive system with both testes directed anteriorly and reflexed posterior testis, and presence of tubular pre-cloacal supplements and pre-cloacal seta. Mudwigglus patumuka gen. et sp. n. is characterised by gubernaculum with dorso-caudal apophyses, vagina directed posteriorly, and short conical tail with three terminal setae. M. macramphidum gen. et sp. n. is characterised by long fovea amphidialis, cylindrical buccal cavity, gubernaculum without apophyses, vagina at right angle to body surface, and conico-cylindrical tail without terminal setae. M. plebeius gen. et sp. n. is characterised by cylindrical buccal cavity with cuticularised ring, gubernaculum with dorso-caudal apophyses, females with vagina directed posteriorly, and conico-cylindrical tail with two terminal setae. Diplopeluta nellyae Vinex and Gourbault, 1992 is transferred to Mudwigglus gen. n. based on observations of paratypes from New Caledonia, and of specimens from the New Zealand continental slope, which both show the presence of two testes facing anteriorly. M. macramphidum gen. et sp. n. was restricted to a single site on Chatham Rise crest (350 m water depth), whereas M. patumuka gen. et sp. was recorded from six sites on western Chatham Rise (350-2800 m). M. plebeius gen. et sp. n. was recorded from 13 sites on Chatham Rise and two sites on Challenger Plateau (264-2300 m). Mudwigglus nellyae comb. n. was restricted to two Challenger Plateau sites. All Mudwigglus gen. n. species appear to be restricted to subsurface sediments.

Case Report: Halicephalobus gingivalis: A Rare Cause of Fatal Meningoencephalomyelitis in Humans

The genus Halicephalobus consists of eight species of free-living nematodes. Only one species (H. gingivalis) has been reported to infect vertebrates. Human infection is extremely rare, and only four cases have been reported in the literature. These nematodes seem to exhibit neurotropism, but their life cycle, mode of infection, and risk factors are poorly understood. Neurohelminthiases are not commonly recognized in the United States and when they do occur, pose great diagnostic challenges because of lack of appropriate non-invasive screening and/or confirmatory tests. We report a challenging case of meningoencephalomyelitis caused by a Halicephalobus sp., in which the patient had a rapidly deteriorating clinical course. The case did not raise any clinical suspicion of neurohelminthiases, although increased eosinophils were present in the cerebrospinal fluid. This case presents an opportunity to highlight the impor- tance of considering parasitic infection in meningoencephalitis or meningoencephalomyelitis presenting atypically.

Halicephalobus gingivalis: A Rare Cause of Fatal Meningoencephalomyelitis in Humans

The genus Halicephalobus consists of eight species of free-living nematodes. Only one species (H. gingivalis) has been reported to infect vertebrates. Human infection is extremely rare, and only four cases have been reported in the literature. These nematodes seem to exhibit neurotropism, but their life cycle, mode of infection, and risk factors are poorly understood. Neurohelminthiases are not commonly recognized in the United States and when they do occur, pose great diagnostic challenges because of lack of appropriate non-invasive screening and/or confirmatory tests. We report a challenging case of meningoencephalomyelitis caused by a Halicephalobus sp., in which the patient had a rapidly deteriorating clinical course. The case did not raise any clinical suspicion of neurohelminthiases, although increased eosinophils were present in the cerebrospinal fluid. This case presents an opportunity to highlight the importance of considering parasitic infection in meningoencephalitis or meningoencephalomyelitis presenting atypically.

One new genus and two new free-living nematode species (Desmodorida, Desmodoridae) from the continental margin of New Zealand, Southwest Pacific Ocean

One new genus and two new species of the family Desmodoridae are described from the upper continental slope of New Zealand, at 350-1240 m water depths. Onepunema gen. n. is characterised by a striated head capsule, small buccal cavity without teeth, and presence of two testes. Onepunema gen. n. can be differentiated from all other genera of the family by the presence of two testes, which is an exception to the holapomorphic character (i.e. monorchic males) of the Desmodoroidea. Onepunema enigmaticum gen. et sp. n. shares characters typical of the subfamilies Spiriniinae (small buccal cavity without distinct teeth) and Desmodorinae (presence of head capsule). Onepunema gen. n. is placed within the Desmodorinae based on the latter trait, which is never found within the Spiriniinae. The type species, Onepunema enigmaticum gen. et sp. n., is characterised by the presence of two laterodorsal and two lateroventral rows of pores with conspicuous ducts, slender pharynx with rounded terminal bulb, presence of two types of cells in intestinal epithelium, and presence of four or five pre-cloacal supplements consisting of thickened areas of cuticle in males. The genus Pseudonchus is recorded for the first time from the deep sea (1240 m water depth) and from the New Zealand region. Pseudonchus virginiae sp. n. is characterised by its stout body, short cephalic setae, monospiral amphideal fovea, short arcuate spicules with capitulum, five regularly-spaced precloacal setae, and short conical tail. A key to all known valid species of the genus Pseudonchus is provided.

Two new free-living nematode species (Comesomatidae) from the continental slope of New Zealand, with keys and notes on distribution

Two new free-living nematode species (Comesomatidae) from the continental slope of New Zealand, with keys and notes on distribution

Deep-sea nematodes (Comesomatidae) from the Southwest Pacific Ocean: five new species and three new species records

The present study describes five new free-living nematode species and provides three new species records of the family Comesomatidae (genera Cervonema Wieser, 1954, Dorylaimopsis Ditlevsen, 1918, Hopperia Vitiello, 1969, and Kenyanema Muthumbi et al., 1997) from the continental margin of New Zealand, Southwest Pacific. Dichotomous identification keys are provided for all known species of Dorylaimopsis and Hopperia. Cervonema shiae Chen & Vincx, 2000 is recorded for the first time outside the type locality (Beagle Channel, Chile). C. kaikouraensis sp. nov. is characterised by amphideal fovea with 5.5 turns situated at 1.7 head diameter from anterior end, jointed outer labial setae, equal in length to cephalic setae, sperm dimorphism, and 5-6 small pre-cloacal supplements. C. multispira sp. nov. is characterised by amphideal fovea with 8.0-8.5 turns situated at 2.6-4.0 head diameter from anterior end, cephalic setae 2-3 μm long, slightly shorter than outer labial setae, presence of six uninucleated cells in males (potentially pseudocoelomocytes or supplementary excretory cells), 5 small pre-cloacal supplements, and strongly cuticularised, arcuate spicules with capitulum. C. proberti sp. nov. is characterised by amphideal fovea with 5 turns and located at < 1 head diameter from anterior end, cephalic setae 1.6-2.0 times longer than outer labial setae, and 8 small pre-cloacal supplements. Dorylaimopsis nodderi sp. nov. is characterised by cuticle with lateral differentiation consisting of three longitudinal rows of larger dots in the pharyngeal and caudal regions, two rows of larger dots in middle region of body, and spicules with rounded ventral projection at one third of spicule length from distal end, giving appearance of a joint. Hopperia ancora sp. nov. is characterised by short conical cephalic setae, spicules with hook-like projection at distal end, gubernaculum with bent apophyses, and 11-13 pre-cloacal supplements. H. beaglense Chen & Vincx, 1998 is recorded from Kaikoura Canyon, the first record of this species outside the type locality (Beagle Channel, Chile). Kenyanema monorchis Muthumbi et al., 1997 is also recorded for the first time outside the type locality (Indian Ocean).

A new species of the genus Calodorylaimus (Nematoda, Dorylaimida) from highly mineralised rivers of the Elton Lake basin, Russia

A new species of free-living nematode (Calodorylaimus salinus sp. nov.), found in sediment of the highly mineralised rivers of the Elton lake basin (Russia), is described and illustrated. This species is close to C. mongolicus Andrássy, 1988, but differs from the latter in having a wider labial region, a stouter tail in females and a greater number of separate precloacal supplements in males. A dichotomic key for identification of valid species of the genus CalodorylaimusAndrássy, 1986 is given. Calodorylaimus densus Andrássy, 1988 is assigned to the genus Laimydorus Siddiqi, 1969.

Two new free-living nematode species (Comesomatidae) from the continental slope of New Zealand, with keys and notes on distribution

Two new free-living marine nematode species of the family Comesomatidae are described from the continental slope of NewZealand, and their distributions at 32 sites are investigated in relation to environmental factors. Vasostoma aurata n. sp. is char-acterised by a distinctly set-off head, amphideal fovea with 4.5 turns, conspicuous chords consisting of two bands fusing atbody extremities, with outline of cell bodies usually golden-coloured, and relatively short spicules. Setosabatieria conicauda n.sp. is characterised by an amphid with 4.25–4.5 turns, the presence of only 1–3 sub-cephalic setae per file, several clusters ofintracellular inclusions, sometimes brown-coloured, in the intestinal wall, and a conical tail. Keys to all known species of Seto-sabatieria and Vasostoma are provided. Both species were mostly restricted to subsurface (1–5cm depth) sediments. The abun-dance of V. aurata n. sp. and S. conicauda n. sp. was significantly correlated with food quantity and quality, but the patternsdiffered between species. The effect of food-related factors may be directly linked to interspecific differences in food require-ments, or mediated by biogeochemical processes (i.e., tolerance of sub-surface oxygen and sulphide concentrations). No signif-icant correlations were found between sediment granulometry and abundances, despite the wide range of sediment grain-sizes (6–93% silt and clay) at the sampling sites.

Free-living nematodes of the Tra Ly River in the Red River mouth, Vietnam

In samples of the Tra Ly River in the Red River mouth (Northern Vietnam), 46 species of free-living nematodes have been found, five of which are new to science. The species dominant in abundance were Ptycholaimellus adocius Dashchenko et Belogurov, 1984; Dichrocuadora affinis Gagarin et Nguyen Vu Thanh, 2011; and Tripyloides minor sp.n. The species composition of nematodes is listed and the new species Tripyloides minor sp. n. is described and illustrated. The nematode described and illustrated by Riemann (1970) from watercourses of Colombia as Tripyloides amazonicus (Gerlach, 1957) is recognized as a valid species (Tripyloides riemanni nom.n).

Molecular Diversity of Fungal Phylotypes Co-Amplified Alongside Nematodes from Coastal and Deep-Sea Marine Environments

Nematodes and fungi are both ubiquitous in marine environments, yet few studies have investigated relationships between these two groups. Microbial species share many well-documented interactions with both free-living and parasitic nematode species, and limited data from previous studies have suggested ecological associations between fungi and nematodes in benthic marine habitats. This study aimed to further document the taxonomy and distribution of fungal taxa often co-amplified from nematode specimens. A total of 15 fungal 18S rRNA phylotypes were isolated from nematode specimens representing both deep-sea and shallow water habitats; all fungal isolates displayed high pairwise sequence identities with published data in Genbank (99–100%) and unpublished high-throughput 454 environmental datasets (>95%). BLAST matches indicate marine fungal sequences amplified in this study broadly represent taxa within the phyla Ascomycota and Basidiomycota, and several phylotypes showed robust groupings with known taxa in phylogenetic topologies. In addition, some fungal phylotypes appeared to be present in disparate geographic habitats, suggesting cosmopolitan distributions or closely related species complexes in at least some marine fungi. The present study was only able to isolate fungal DNA from a restricted set of nematode taxa; further work is needed to fully investigate the taxonomic scope and function of nematode-fungal interactions.

Some data on the fauna of free-living nematodes of Lake Biwa (Japan)

In samples from Lake Biwa (Japan), a total of 23 free-living nematode species have been found, two of them new to science. The family Tobrilidae was the most diverse in taxonomic composition: seven species from three genera. Dorylaimus stagnalis Dujardin was the dominant species in regards to number of specimens in samples. Descriptions and drawings of the new species Tripyla grygieri sp. n. are presented.

A new genus and two new species of marine free-living nematodes from the coastal waters of Southern Vietnam

A new genus and two new species of free-living marine nematodes from sediments in the coastal zone of the South China Sea (Vietnam) are described. Cyartonemoides gen. n. morphologically resembles Cyartonema Cobb, 1920, but differs from it in having a well-developed cephalic capsule. Cyartonemoides foetidus gen. n., sp. n. is the type and the only species of the genus. Campylaimus abnormis sp. n. differs from all species of the genus Campylaimus Cobb, 1920 by the shape of the amphidial fovea and shorter lateral fields.