Review of Euchromadorinae (Nematoda: Chromadorida) with description of a new species of Trochamus Boucher & De Bovée, 1971 from the Sundarban, India.

Diagnostic characters for all 11 valid genera of Euchromadorinae are presented with taxonomic key on the basis of morphology of male copulatory apparatus, cuticular pattern, amphideal fovea, and buccal onchia. The key to the species of Trochamus spp. is also constructed with the description of T. timmi sp. n. from the mud-flat of Sundarban, India. The newly described species is different from other Trochamus spp. on the basis of the appearance of lateral differentiation of cuticle, long curved spicule, simple gubernaculum and the presence of pre-cloacal modification in male.

Descriptions of Leptolaimus sinensis sp. nov. and Perspiria brevicaudata sp. nov. (Nematoda) from the Yellow Sea, China.

Two new free-living marine nematodes which were collected at silt beach of Rizhao along the Yellow Sea are identified here as Leptolaimus sinensis sp. nov. and Perspiria brevicaudata sp. nov. Leptolaimus sinensis sp. nov. is characterized by annulated cuticle with lateral alae, 2 µm in width; buccal cavity cylindrical; cephalic setae 2 µm long; amphidial fovea unispiral, circular in outline; six to seven evenly spaced tubular precloacal supplements and 23-29 continuous alveolar supplements extending from cloaca to level of the base of buccal cavity; spicules slender, slightly arcuate; gubernaculum with dorso-caudal apophysis; tail conico-cylindrical, about 6 times cloacal body diameter in males and elongated in females, about 9 times anal body diameter in length. Perspiria brevicaudata sp. nov. is characterized by having four cephalic setae and four cervical setae; small buccal cavity with dorsal tooth and minute ventral tooth; amphidial fovea unispiral, looking like double circle in outline, surrounded partially by cuticle striations; spicules arcuate with ventral velum, handle-like proximally and tapered distally; gubernaculum plate-shaped, without apophysis; twelve winged precloacal supplements present. Updated identification keys for group of Leptolaimus species characterized by the presence of both alveolar and tubular precloacal supplements and for species of Perspiria are also given.

Two new species of Cyatholaimidae (Nematoda: Chromadorida) from the Southeastern Brazilian coast with emphasis on the pore complex and lateral pore-like structures.

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.

Host identity is the dominant factor in the assembly of nematode and tardigrade gut microbiomes in Antarctic Dry Valley streams.

Recent work examining nematode and tardigrade gut microbiomes has identified species-specific relationships between host and gut community composition. However, only a handful of species from either phylum have been examined. How microbiomes differ among species and what factors contribute to their assembly remains unexplored. Cyanobacterial mats within Antarctic Dry Valley streams host a simple and tractable natural ecosystem of identifiable microinvertebrates to address these questions. We sampled 2 types of coexisting mats (i.e., black and orange) across four spatially isolated streams, hand-picked single individuals of two nematode species (i.e., Eudorylaimus antarcticus and Plectus murrayi) and tardigrades, to examine their gut microbiomes using 16S and 18S rRNA metabarcoding. All gut microbiomes (bacterial and eukaryotic) were significantly less diverse than the mats they were isolated from. In contrast to mats, microinvertebrates' guts were depleted of Cyanobacteria and differentially enriched in taxa of Bacteroidetes, Proteobacteria, and Fungi. Among factors investigated, gut microbiome composition was most influenced by host identity while environmental factors (e.g., mats and streams) were less important. The importance of host identity in predicting gut microbiome composition suggests functional value to the host, similar to other organisms with strong host selected microbiomes.

Chromaspirina aliapapillata sp.nov. (Nematoda, Desmodorida) from Donuzlav Bay (Crimea, Black Sea).

A new species of free-living marine nematode Chromaspirina aliapapillata sp. nov. from the Donuzlav Bay (Black Sea) is described. Chromaspirina aliapapillata sp. nov. is characterized by a slender body, buccal cavity with two dorsal teeth, spiral amphids, tail conico-cylindrical and presence of precloacal supplements. The new species differs from other known species of the genus by having two dorsal teeth and presence of 17 to 21 precloacal supplements of which one or two are cup-shaped and rest curved tubes.

Differential regulation of degradation and immune pathways underlies adaptation of the ectosymbiotic nematode Laxus oneistus to oxic-anoxic interfaces.

Eukaryotes may experience oxygen deprivation under both physiological and pathological conditions. Because oxygen shortage leads to a reduction in cellular energy production, all eukaryotes studied so far conserve energy by suppressing their metabolism. However, the molecular physiology of animals that naturally and repeatedly experience anoxia is underexplored. One such animal is the marine nematode Laxus oneistus. It thrives, invariably coated by its sulfur-oxidizing symbiont Candidatus Thiosymbion oneisti, in anoxic sulfidic or hypoxic sand. Here, transcriptomics and proteomics showed that, whether in anoxia or not, L. oneistus mostly expressed genes involved in ubiquitination, energy generation, oxidative stress response, immune response, development, and translation. Importantly, ubiquitination genes were also highly expressed when the nematode was subjected to anoxic sulfidic conditions, together with genes involved in autophagy, detoxification and ribosome biogenesis. We hypothesize that these degradation pathways were induced to recycle damaged cellular components (mitochondria) and misfolded proteins into nutrients. Remarkably, when L. oneistus was subjected to anoxic sulfidic conditions, lectin and mucin genes were also upregulated, potentially to promote the attachment of its thiotrophic symbiont. Furthermore, the nematode appeared to survive oxygen deprivation by using an alternative electron carrier (rhodoquinone) and acceptor (fumarate), to rewire the electron transfer chain. On the other hand, under hypoxia, genes involved in costly processes (e.g., amino acid biosynthesis, development, feeding, mating) were upregulated, together with the worm's Toll-like innate immunity pathway and several immune effectors (e.g., bactericidal/permeability-increasing proteins, fungicides). In conclusion, we hypothesize that, in anoxic sulfidic sand, L. oneistus upregulates degradation processes, rewires the oxidative phosphorylation and reinforces its coat of bacterial sulfur-oxidizers. In upper sand layers, instead, it appears to produce broad-range antimicrobials and to exploit oxygen for biosynthesis and development.

Inverted base composition skews and discontinuous mitochondrial genome architecture evolution in the Enoplea (Nematoda).

BACKGROUND: Within the class Enoplea, the earliest-branching lineages in the phylum Nematoda, the relatively highly conserved ancestral mitochondrial architecture of Trichinellida is in stark contrast to the rapidly evolving architecture of Dorylaimida and Mermithida. To better understand the evolution of mitogenomic architecture in this lineage, we sequenced the mitogenome of a fish parasite Pseudocapillaria tomentosa (Trichinellida: Capillariidae) and compared it to all available enoplean mitogenomes. RESULTS: P. tomentosa exhibited highly reduced noncoding regions (the largest was 98 bp), and a unique base composition among the Enoplea. We attributed the latter to the inverted GC skew (0.08) in comparison to the ancestral skew in Trichinellidae (-0.43 to -0.37). Capillariidae, Trichuridae and Longidoridae (Dorylaimida) generally exhibited low negative or low positive skews (-0.1 to 0.1), whereas Mermithidae exhibited fully inverted low skews (0 to 0.05). This is indicative of inversions in the strand replication order or otherwise disrupted replication mechanism in the lineages with reduced/inverted skews. Among the Trichinellida, Trichinellidae and Trichuridae have almost perfectly conserved architecture, whereas Capillariidae exhibit multiple rearrangements of tRNA genes. In contrast, Mermithidae (Mermithida) and Longidoridae (Dorylaimida) exhibit almost no similarity to the ancestral architecture. CONCLUSIONS: Longidoridae exhibited more rearranged mitogenomic architecture than the hypervariable Mermithidae. Similar to the Chromadorea, the evolution of mitochondrial architecture in enoplean nematodes exhibits a strong discontinuity: lineages possessing a mostly conserved architecture over tens of millions of years are interspersed with lineages exhibiting architectural hypervariability. As Longidoridae also have some of the smallest metazoan mitochondrial genomes, they contradict the prediction that compact mitogenomes should be structurally stable. Lineages exhibiting inverted skews appear to represent the intermediate phase between the Trichinellidae (ancestral) and fully derived skews in Chromadorean mitogenomes (GC skews = 0.18 to 0.64). Multiple lines of evidence (CAT-GTR analysis in our study, a majority of previous mitogenomic results, and skew disruption scenarios) support the Dorylaimia split into two sister-clades: Dorylaimida + Mermithida and Trichinellida. However, skew inversions produce strong base composition biases, which can hamper phylogenetic and other evolutionary studies, so enoplean mitogenomes have to be used with utmost care in evolutionary studies.

Two new species of Acantholaimus (Nematoda, Chromadoridae) from the deep southeastern Atlantic (Santos Basin).

Two new species of the genus Acantholaimus (Nematoda, Chromadoridae) are described from the South Atlantic, in the Santos Basin off the slope of southeastern Brazil. Acantholaimus pugious sp. n. is characterized by a narrow and elongated anterior end; teeth that are thin and long stylet-like (two in number), amphidial fovea located far from the anterior end and occupying most of the corresponding body diameter. Acantholaimus bidentatus sp. n. is characterized by a narrow anterior end, cuticle with more evident dots on both body extremities (up to amphidial fovea and tail); two long, protractible thin teeth (similar to stylet), with curved proximal part. The two species are similar in the shape of the teeth. The teeth morphology may be correlated to the process of adaptive convergence of these species. An emended diagnosis of the genus is provided.

Two new species of Xyalidae (Nematoda: Monhysterida) from intertidal zone of the Bohai Sea, China.

Two new nematode species are described from the intertidal zone of the Bohai Sea, China. Paramonohystera gracilis sp. nov. is characterized by slender body with a long filiform tail; oval amphidial fovea 6 µm in diameter; spicules slender, 3.4 a.b.d. long; gubernaculum small, plate shaped without apophysis. It differs from the most similar species P. riemanni (Platt, 1973) Lorenzen, 1977 by much slender body and longer filiform tail. Amphimonhystrella boucheri sp. nov. is characterized by short body, deep buccal cavity with funnel shaped anterior portion, circular amphids, conico-cylindrical tail with two thirds conical anterior portion and a third cylindrical posterior portion, small spicules L-shaped and gubernaculum with short apophysis. It is distinguished from the most similar species A. unita Lorenzen, 1977 in buccal cavity funnel shaped, small amphidial fovea circular, spicules short with tapered distal end. Updated keys for valid species of Paramonohystera and Amphimonhystrella are provided.

An Updated Checklist of Free-living Marine Nematodes from Coastal India.

The present study provides an updated species list of free-living marine nematodes reported from coastal India (Coasts and Islands) based on the thorough consultation of literature published from 1956 to 2022. This exercise resulted in a total of 617 valid species belonging to 266 genera, 48 families, 21 superfamilies and 9 orders. Class Chromadorea comprises 487 species represented by 205 genera, while class Enoplea includes 130 species belonging to 61 genera. The most common family was Xyalidae, with 76 species and the least common families having a single species each were represented by Aegialoalaimidae, Rhadinematidae, Aphanolaimidae, Rhabditidae, Pandolaimidae and Rhabdodemaniidae. The checklist provides a robust framework for the distribution and biogeography of free-living marine nematodes from the Indian waters and could be used to relate with marine ecosystems of other countries.

Profiling the Proteome of Cyst Nematode-Induced Syncytia on Tomato Roots.

Cyst nematodes are important herbivorous pests in agriculture that obtain nutrients through specialized root structures termed syncytia. Syncytium initiation, development, and functioning are a research focus because syncytia are the primary interface for molecular interactions between the host plant and parasite. The small size and complex development (over approximately two weeks) of syncytia hinder precise analyses, therefore most studies have analyzed the transcriptome of infested whole-root systems or syncytia-containing root segments. Here, we describe an effective procedure to microdissect syncytia induced by Globodera rostochiensis from tomato roots and to analyze the syncytial proteome using mass spectrometry. As little as 15 mm2 of 10-µm-thick sections dissected from 30 syncytia enabled the identification of 100-200 proteins in each sample, indicating that mass-spectrometric methods currently in use achieved acceptable sensitivity for proteome profiling of microscopic samples of plant tissues (approximately 100 µg). Among the identified proteins, 48 were specifically detected in syncytia and 7 in uninfected roots. The occurrence of approximately 50% of these proteins in syncytia was not correlated with transcript abundance estimated by quantitative reverse-transcription PCR analysis. The functional categories of these proteins confirmed that protein turnover, stress responses, and intracellular trafficking are important components of the proteome dynamics of developing syncytia.

A new genus and species of the family Microlaimidae (Nematoda: Chromadorea) from intertidal sand of the Jeju Island, South Korea.

As a part of the study of marine nematofauna of a sandy intertidal zone of Jeju Island (South Korea), a number of species have been proven as new for science. Here a new species representing a new genus of the family Microlaimidae (Chromadorea), Jejulaimus sinyangensis gen. n., sp. n. is described. The new monotypic genus is characterized by head set off abruptly from the body; anterior sensilla pattern 6+10, where six outer labial setiform sensilla together with four longer cephalic setiform sensilla are integrated in a common crown; pharyngostoma armed with a dorsal tooth and surrounded by convex muscular pharyngeal tissue, forming an anterior pharyngeal bulb which is distinctly set off from the rest of the pharynx; terminal pharyngeal bulb oval; ventral pore and ampulla of the excretory-secretory gland situated just posterior to the nerve ring; an only anterior testis present. The new genus bears some resemblance to the genera Bolbolaimus, Pseudomicrolaimus and Spirobolbolaimus in having an anterior pharyngeal bulb and in the position of the ventral pore of the excretory/secretory gland, but differs from them by anterior sensilla pattern 6+10, absence of subventral teeth in buccal cavity, and monorchic condition of male reproductive system.

Two new species of nematodes from shallow and deep-water sediments in the South China Sea.

Two new species of free-living marine nematodes from the South China Sea are described: Gomphionema setiforme sp. nov. from intertidal sediment and Paracomesoma longissimum sp. nov. from upper continental slope sediment. Gomphionema setiforme sp. nov. is characterized by the punctated cuticle without lateral differentiation and cuticular pores; short cephalic setiform sensilla; spiral amphideal fovea with 4 turns close to the anterior body extremity; large cuticularized buccal cavity with a massive dorsal tooth; pharynx with a large posterior bulb; short, curved spicules; knife-like gubernaculum without apophyses and 11 cup-shaped precloacal supplements. Paracomesoma longissimum sp. nov. is characterized by cuticle with transverse rows of fine punctuations without lateral differentiation; buccal cavity with three teeth; lateral outer labial setiform sensilla 1.5 times as long as the other four outer labial setiform sensilla; spiral amphideal fovea with 2.5 turns; spicules 350360 m long or 15.716 times cloacal body diameter; plate-like gubernaculum without apophyses and 2528 papilliform precloacal supplements.

One new species of free-living marine nematode from the Yellow Sea, China.

A new species of Setostephanolaimus Tchesunov, 1994, S. longiseta sp. nov. was discovered in an intertidal sand beach along the Rizhao coast of the Yellow Sea. It is characterized by its long and slender body, long cephalic setae (longer than 20 m and 16 m in males and females, respectively) and subcephalic setae, long spicules (longer than 90 m), gubernaculum with dorsal hooked apophyses, along with presence of 1012 tubular precloacal supplements in males. Updated dichotomous key for species of the genus Setostephanolaimus is also given.

New chromadorid nematodes from Brazilian coral reefs: a taxonomic contribution to Chromadora Bastian, 1865.

A study involving experiments on a natural Brazilian coral reef, with the aim of assessing the impacts that may be caused by an increase in sea level on benthic fauna, showed that Chromadoridae Filipjev, 1917 was the most abundant and diverse family of Nematoda. Our results also showed that Chromadora Bastian, 1865 was the most abundant and diverse genus, represented by three species: C. serrambi sp. nov., C. pernambucana sp. nov. and C. macrolaimoides Steiner, 1915. Chromadora serrambi sp. nov. is the only Chromadora species where pre-cloacal supplements are absent. Chromadora pernambucana sp. nov. is differentiated by gubernaculum shape and by three supplements, of which two are cup-shaped (small and slightly sclerotized) and a pre-cloacal papilla very close to the cloaca. Chromadora macrolaimoides is very similar to specimens described previously. Here, we propose a grouping of species based on features considered to be most relevant for species identification and present it as an illustrated guide. The diagnostic characteristics of all species were considered, and following discussions, C. micropapillata was revalidated. Finally, the most relevant diagnostic characteristics for the differentiation of Chromadora species were highlighted.

Molecular characterization of free-living nematodes from Kermadec Trench (Nematoda: Aegialoalaimidae, Xyalidae) with description of emAegialoalaimus/em emtereticauda/em n. sp.

The Kermadec Trench is the world's fifth deepest trench and extends from approximately 26 to 36°S near the northeastern tip of New Zealand's North Island. Here, we describe a new species of Aegialoalaimus, a nematode genus with unusual buccal cavity and pharynx morphology, from a site at 9540 metres water depth in Kermadec Trench, and provide the first SSU and D2-D3 of LSU sequences for Aegialoalaimus, Manganonema, Metasphaerolaimus constrictus and Daptonema amphorum. Aegialoalaimus tereticauda n. sp. is characterised by body length 755-864 µm, cephalic sensilla papilliform ( 1 µm long), excretory pore located slightly anterior to posterior bulb in males and slightly anterior to nerve ring in females, arcuate spicules 18-22 µm long, gubernaculum present, precloacal supplements absent, and cylindrical tail 58-64 µm long with rounded tip. Relationships between Aegialoalaimus and Chromadorean orders could not be elucidated based on our SSU analysis; no link could be found with the Plectida, where the Aegialoalaimidae is currently placed, or with the Isolamiida or Cylindrolaimus (Areaolaimida), which share a similar and unusual buccal and pharynx morphology. Our SSU phylogenetic analysis confirms the placement of Manganonema within the Xyalidae, although relationships with other xyalid genera remain unclear. The Sphaerolaimidae formed a clade together with the Monhysteridae, which contradicts the current classification where the Sphaerolaimidae and Xyalidae are classified together into the superfamily Sphaerolaimoidea and the Monhysteridae into the Monhysteroidea. Although limited research has been conducted on the nematode diversity in Kermadec Trench to date, the available data show that half of all invertebrate species known from the trench are nematodes, which highlights the importance of conducting further taxonomic research on this group in hadal environments.

emEubostrichopsis/em emjohnpearsei/em n. gen., n. sp., the first stilbonematid nematode (Nematoda, Desmodoridae) from the US West Coast.

A new genus of the marine Stilbonematinae (Nematoda, Desmodoridae) is described from the Pacific coast of the United States of America. The worms inhabit the sulfidic sediment among the roots of the surfgrass Phyllospadix sp. in the rocky intertidal. The ectosymbiotic coat is of a new type for Stilbonematinae. It consists of rod-shaped bacteria pointed at both poles densely attached with one pole to the host cuticle. This is the first report of this symbiotic nematode subfamily from the US West Coast.

A Helminth Survey of Northern Bobwhite Quail (Colinus virginianus) and Passerines in the Rolling Plains Ecoregion of Texas.

The Northern bobwhite quail (Colinus virginianus) is a popular game bird that has been experiencing a well-documented decline throughout Texas since the 1960s. While much of this decline has been attributed to habitat loss and fragmentation, recent studies have identified other factors that may also contribute to decreasing quail populations. Parasites, in particular, have become increasingly recognized as possible stressors of quail, and some species, particularly the eyeworm (Oxyspirura petrowi) and cecal worm (Aulonocephalus pennula) are highly prevalent in Texas quails. Eyeworm infection has also been documented in some passerines, suggesting helminth infection may be shared between bird species. However, the lack of comprehensive helminth surveys has rendered the extent of shared infection between quail and passerines in the ecoregion unclear. Thus, helminth surveys were conducted on bobwhite, scaled quail (Callipepla squamata), Northern mockingbirds (Mimus polyglottos), curve-billed thrashers (Toxistoma curvirostre), and Northern cardinals (Cardinalis cardinalis) to contribute data to existing parasitological gaps for birds in the Rolling Plains ecoregion of Texas. Birds were trapped across 3 counties in the Texas Rolling Plains from March to October 2019. Necropsies were conducted on 54 individuals (36 quail and 18 passerines), and extracted helminths were microscopically identified. Nematode, cestode, and acanthocephalan helminths representing at least 10 helminth species were found. Specifically, A. pennula and O. petrowi had the highest prevalence, and O. petrowi was documented in all of the study species. This research adds to the body of knowledge regarding parasitic infections in quail and passerines of the Rolling Plains ecoregion and highlights the potential consequences of shared infection of eyeworms among these bird species.

A detailed taxonomic study on two new and one known species of Anaplectus De Coninck Schuurmans Stekhoven, 1933 (Nematoda: Plectidae).

This paper provides descriptions of two new and one known species of the genus Anaplectus De Coninck Schuurmans Stekhoven, 1933. Anaplectus sudhausi sp. nov. is characterised by leaf-shaped lips interspersed with interlabial liplets; bifid apices of the lateral lips; cheilostom with non-cuticularised walls; gymnostom with cuticularised arcuate walls; 120-132 sublateral hypodermal glands on each body side with an additional 5-8 smaller subdorsal hypodermal glands; female tail with three caudal setae; males with arcuate spicules having manubrium slightly wider than calomus or blade, last median tubulus or supplement about half the spicule length and tail terminus with a weakly cuticularised spinneret. A. labiosulcus sp. nov. is characterised by 115-123 sublateral hypodermal glands on each side of the body with those on the dorsal side usually larger than the ventrals; the 5-6 anteriormost glands are unpaired and arranged linearly; lips with cuticularised interlabial grooves; gymnostom arched, occasionally double-arched and caudal glands grouped and opening through a cuticularised spinneret. A. granulosus (Bastian, 1865) De Coninck Schuurmans Stekhoven, 1933 has been redescribed with some minor differences from previous descriptions.

Two species of the genus Theristus Bastian, 1865 (Nematoda: Xyalidae) from the hypersaline water bodies of the Crimea (Azov-Black Sea basin).

Morphological descriptions of two species of the genus Theristus Bastian, 1865 belonging to group flevensis, found in the hypersaline water bodies of the Crimean Peninsula, are presented. Theristus siwaschensis sp. n. is morphologically closest to T. flevensis Schuurmans Stekhoven, 1935, T. parambronensis Timm, 1952, T. macroflevensis Gerlach, 1954, T. metaflevensis Gerlach, 1955, but differs from them by the structure of the reproductive system in females, number of cephalic setae and size of spicules. Specimens of T. flevensis found in the Lake Chersonesskoye are similar to the re-description of a large forms of T. flevensis from Chile by Murhy (1966) and Caspian Sea by Chesunov (1981). However, it differs from the Caspian Sea species by having larger amphids, longer cephalic setae and spicules. T. pratti Murph Canaris, 1964 and T. ambronensis Schulz, 1937 are synonymized with T. flevensis.