Search Results (172)

The phylum Nematoda is host to a vast and diverse virosphere, yet severe viral diseases are rarely observed. This paradox between pervasive infection and limited pathology suggests the existence of a highly effective host–virus “truce”. In this review, we argue that this truce is not a result of viral attenuation but is actively arbitrated by a multi-tiered host immune network, whose primary characteristic is not destructive power but exquisite cost–benefit management. We deconstruct this network into two functional tiers. The first, the “effector layer”, comprises a diverse arsenal of antiviral pathways, including RNA interference (RNAi), the Intracellular Pathogen Response (IPR), and other direct-acting mechanisms. The second, the “regulatory layer”, acts as a command hub, integrating internal physiological states—such as metabolism and aging—with external threat signals to orchestrate a proportional defense, thereby mitigating the high fitness costs of immunity. Understanding this intricate network is critical, as it not only explains the dynamics of infection within nematodes but also has profound implications for a broader medical landscape, particularly through the “Trojan Horse” effect, where nematode-borne viruses might elicit immune responses in their final vertebrate hosts. Together, these insights provide a unified framework for studying nematode–virus interactions and for comparing antiviral strategies across metazoans. Full article

Two new species of free-living marine nematodes from mangrove wetlands of Beihai, Guangxi province in China, are described and illustrated. Trissonchulus sinensis sp. nov. is characterized by a head continuous with the body, an amphidial fovea pouch-shaped, pharynx expanding gradually but not forming a posterior bulb, spicules sclerotized, blade-shaped, slightly curved ventrally, proximal part enlarged with a prominent central septum, posterior part slender and handle-like; gubernaculum small, composed of two distally connected sheet-like structures with tooth-like ends, and lacking apophysis. Metachromadora sinica sp. nov. is characterized by a cuticle that is finely annulated, labial sensilla papilliform, cephalic setae four in number, amphideal fovea loop-shaped, exhibiting a double-contoured appearance, pharyngeal bulb well-developed, internal cuticular lumen tripartite, lateral epidermal ridges present, spicules slender with an enlarged capitulum, gubernaculum boat-shaped, precloacal supplements absent, tail conical with two setose protuberances, three pairs of subventral preanal setae, and a pair of papillae situated anterior to the anus. Nearly full-length SSU sequences and D2-D3 of LSU sequences are provided for the new species. Phylogenetic analysis of SSU provided support for the current classification status of the two new species. In the SSU phylogenetic tree, the family Ironidae was recovered as a separate monophyletic clade. However, the phylogenetic relationships within the family Desmodoridae were complicated, and the subfamilies Desmodorinae and Spiriniinae were polyphyletic. A comprehensive taxonomic approach combining morphological observations and molecular phylogeny construction would be particularly valuable in a more robust nematode taxonomy. Full article

The AGC kinases constitute a large and ancient gene superfamily with origins that coincided with the appearance of multicellularity. Three AGC kinase families—protein kinase A (PKA), protein kinase G (PKG), and protein kinase C (PKC)—mediate the actions of neuropeptide hormones, biogenic amines, and other ligands on various physiological processes in metazoans. Metazoans express two PKG types. Jawed vertebrates express three PKA catalytic (C) subunits, four regulatory (R) subunits, and twelve PKCs, organized into conventional, novel delta-like, novel epsilon-like, atypical, and protein kinase N (PKN) subfamilies. By contrast, invertebrate PKA and PKC sequences are not well characterized. Consequently, limited database resources can result in misidentification or mischaracterization of proteins and can lead to misinterpretation of experimental data. A broad phylogenetic and sequence analysis of CrusTome transcriptome and GenBank databases was used to characterize 640 PKA-C sequences, 1122 PKA-R sequences, and 1844 PKC sequences distributed among the Annelida, Arthropoda, Chordata, Cnidaria, Nematoda, Mollusca, Echinodermata, Porifera, Platyhelminthes, and Tardigrada. Phylogenetic analysis and multiple sequence alignments revealed conservation of certain PKA-C, PKA-R and PKC isoforms across metazoans, as well as diversification of additional taxon-specific isoforms. Decapods expressed four PKA-C isoforms, designated PKA-C₁, -C_D1, -C_GLY1, and -C_GLY2; five PKA-R isoforms, designated PKA-RI₁, -RI_D1, -RII_GLY, and -RII_D1; and five PKC isoforms, designated PKN_D1-3, conventional cPKC_D1, novel nPKC_D1δ and nPKC_D1ε, and atypical aPKC_D1. PKA-C_GLY1, -C_GLY2, and -RII_GLY had glycine-rich N-terminal sequences that were unique to crustaceans. These data suggest lineage-specific diversification that retained the core catalytic function of each kinase, while regions outside of the kinase domain may provide specialized regulatory mechanisms and/or spatiotemporal subcellular localization in invertebrate tissues. Full article

Cyst nematodes of the genus Heterodera are important plant-parasitic nematodes that cause significant crop losses worldwide but are often overlooked due to their non-specific symptoms and complex biology. This study assessed Heterodera diversity in Portugal using an integrative molecular approach based on four genetic markers (mtCOI, 18S rDNA, ITS, and 28S rDNA). Five valid species were identified: Heterodera cruciferae, H. mani, H. schachtii, H. trifolii, and H. zeae, with H. mani reported for the first time in the country. A distinct taxon from Coimbra (central Portugal) may represent a new or unsequenced species, highlighting gaps in reference datasets. Among the markers, mtCOI was the most effective, though some taxa remained unresolved. These results reinforce the value of multi-marker approaches, contribute with new sequences, and improve diagnostic capability for nematode management. Full article

The Mediterranean Sea hosts highly diverse habitats such as Posidonia oceanica meadows, coralligenous communities, and gorgonian forests. Stressors including warming, eutrophication, pollution, and overfishing are driving shifts towards algae-dominated systems, often with reduced biodiversity. Among these, recent research surprisingly revealed that the mat-forming red alga Phyllophora crispa, which overgrows seagrass and gorgonian habitats, supports high sessile invertebrate diversity. However, little is known about its associated non-sessile fauna. This study thus investigated non-sessile invertebrates in P. crispa using a newly designed appropriate sampling technique at two study sites around Giglio Island (Italy), Fenaio, and Secca II (distance ca. 600 m from each other). Across all samples, 5464 organisms were identified, mostly to family level. We recorded 169 non-sessile taxa, including 96 families, 41 copepod morphotypes, 21 ostracod morphotypes, and 11 unclassified taxa. The dominant phyla were Arthropoda (67%), Mollusca (14%), Annelida (9%), and Nematoda (5%). The most abundant families were Calliopiidae (Amphipoda), Leptognathiidae (Malacostraca), and Mytilidae (Bivalvia). Of the 169 taxa, 128 occurred at both sites, while 20 were unique to Fenaio and 21 to Secca II, suggesting high connectivity likely linked to mobility. Organism abundances ranged from 1315 to 5759 individuals per m² seafloor. Diversity indices were as follows: Shannon 1.5–3.4, Simpson 0.6–1.0, and Pielou 0.6–0.9. These values are similar or even exceed previously reported values for sessile invertebrates (Shannon 2.2–2.5). Notably, P. crispa supported diversity levels higher than those reported for seagrass meadows (Shannon 2.0–2.1) and even tropical coral reefs (2.0). Our study thus confirms P. crispa as a biodiversity hotspot and suggests that these algae mats should be considered in biodiversity conservation strategies. Full article

During a survey of the west coast of South Korea, two new Pseudochromadora species were recorded from Yeongjongdo Island. Descriptions of two new species, an updated list of valid species within the genus, a tabular key, partial sequences of mtCOI, near full-length SSU, and the D2–D3 region of LSU rDNA, together with phylogenetic analyses are provided. The two new species are classified as Pseudochromadora based on having a two-portioned cephalic capsule, unispiral amphidial fovea, lateral alae extending from the posterior end of the pharynx as far as the tail, and presence of copulatory thorns, as well as a short conical tail. The two species are distinguished from each other by their different types of labial regions of the cephalic capsule (round-shaped vs. hat-shaped). The two species, despite being found in the same locality, are morphologically and molecularly distinct from one another. Pairwise Kimura 2-parameter (K2P) distances between the two new species were 10.6% (18S) and 27.2% (28S), values consistent with interspecific divergence observed among congeners. Phylogenetic analyses showed both species as distinct lineages within Pseudochromadora. In the 28S rDNA tree, each was retrieved as a well-supported monophyletic clade with congeners, whereas in the 18S tree, all congeners including the two new species formed a single clade, except for P. plurichela, which branched outside the main group. These results highlight potential paraphyly within Pseudochromadora and suggest that overlooked morphological traits may hold phylogenetic significance, warranting further investigation. Full article

As environmental indicators, invertebrate communities are closely related to changes in the water environment. Efficient and accurate monitoring of invertebrates is of great significance for providing references for water environment conservation. However, environmental DNA metabarcoding has rarely been used in invertebrate research at the Chai River in Kunming, Yunnan, China, and the current characteristics of invertebrate communities are unclear. Therefore, this study investigated the spatial and seasonal patterns of invertebrates and the environmental stressors of the Chai River. Based on eDNA metabarcoding, 873 ASVs of invertebrates belonging to Annelida, Arthropoda, Cnidaria, Gastrotricha, Mollusca, Nematoda, Platyhelminthes, Protozoa, and Rotifera were identified, with Arthropoda being the absolute dominant phylum. Distinct spatial and seasonal variations in the invertebrate communities (e.g., ASV number, dominant genera, relative abundances) were observed. Macrothrix and Acanthamoeba were the first and second most dominant genera, both in dry and wet periods. A spatial–seasonal heterogeneity of the relation between the invertebrate communities and environmental factors was observed in the Chai River. The water temperature (WT), chemical oxygen demand (COD), conductivity (C), and Chlorophyll-a (Chl-a) levels were deemed to be the crucial environmental factors influencing the distributions of invertebrate communities in the Chai River, which was consistent with the spatial and seasonal differences in pollution characteristics around the Chai River. This study provides insights into conserving the diversity of invertebrate communities and the management of the Chai River and similar agricultural rivers. Full article

Proteins containing the SQS-PSY domain, which include squalene synthetase (SQS), phytoene synthetase (PSY), and NDUFAF6, are functionally important and widely distributed in plants and animals. However, they have not been previously reported in nematodes. In this study, we identified a gene (Minc31999) encoding an SQS-PSY domain-containing protein in the root-knot nematode Meloidogyne incognita. In silico comparison and enzymatic assays of the recombinant protein indicated that this nematode protein is a putative NDUFAF6 homolog. Phylogenetic analysis revealed that this protein is evolutionarily conserved within the Nematoda phylum. RT-qPCR analysis showed that Minc31999 is highly expressed during the early infection stage of M. incognita. Targeting the nematode gene Minc31999 via host-induced gene silencing (HIGS) significantly hindered nematode development and virulence. In contrast, heterologous expression of Minc31999 in Arabidopsis thaliana disrupted normal plant development and increased host susceptibility to nematode infection. Transcriptomic profiling (RNA-seq) of these transgenic plants prior to infections showed a widespread differential expression of genes across multiple metabolic pathways. We propose that this nematode SQS-PSY domain-containing protein may function as an effector that rewires host secondary metabolism to establish a parasitic relationship. Our study elucidates a novel strategy in nematode–plant interactions and advances our understanding of the functional evolution of SQS-PSY domain-containing proteins. Full article

During a survey of the intertidal zone on the eastern coast of Jeju Island, Korea, a new species of free-living marine nematode belonging to the Selachinematidae (Chromadorida) family was discovered and described. Gammanema papillatum sp. nov. is morphologically most similar to G. lunatum and G. agglutinans, both recorded from New Zealand, by sharing a loop-shaped amphid in males, unlike the multispiral amphid typical of most congeners, and the presence of cuticular spines. It differs from G. lunatum in body length (1122–1366 µm vs. 754–1196 µm), a-ratio (21–23 vs. 13–15), shape of the supplementary organs (papilla-shaped vs. cup-shaped), and distance from the posterior-most supplement to the cloacal opening (58–63 µm vs. 18–32 µm). In terms of precloacal supplementary organ morphology, the new species also resembles Gammanema conicauda, as both are the only congeners with papilla-shaped precloacal supplementary organs. However, G. papillatum sp. nov. differs from G. conicauda by the number of supplementary organs (7–8 vs. 22), amphidial shape (loop-shaped vs. unispiral), and the presence of cuticular spines (absent in G. conicauda). Near full-length SSU and D2–D3 region LSU rDNA sequences were obtained for the new species. Molecular analyses revealed the lowest divergence from G. lunatum (SSU: 1.7%; LSU: 19.8%), with greater divergence from other congeners (SSU: 4.0–4.6%; LSU: 30.5–37.1%). This represents the second record of Gammanema from Korean waters and provides new insights into trait combinations that may help define a subgroup within the genus. Full article

Lance nematodes, Hoplolaimus spp., feed on the roots of many kinds of plants, including agronomic crops. In this study, morphological and molecular analyses of several Hoplolaimus species and populations are provided. We were able to collect and characterize the topotype materials of H. galeatus from Arlington, Virginia; H. stephanus syn. n. from Nichols, South Carolina; and H. concaudajuvencus from Pensacola, Florida, and several additional populations and species from the United States, Israel, and India. Phylogenetic analyses of several hundred sequences of the D2–D3 expansion regions of 28S rRNA, ITS rRNA, and COI genes of Hoplolaimus species obtained from published and original datasets were given. Fifty-three new D2–D3 of 28S rRNA, 43 new ITS rRNA, and 47 new COI sequences from 23 isolates of Hoplolaimus spp. and one isolate of Peltamigratus christiei were obtained in this study. New molecular identities for H. concaudajuvencus and H. galeatus were proposed. Hoplolaimus stephanus syn. n. was considered a synonym of H. galeatus based on the morphological and molecular similarity of these two species. Analysis of morphology and molecular data did not reveal significant differences among H. columbus syn. n., H. indicus syn. n., and H. seinhorsti, and the first two species were synonymized with H. seinhorsti. A new species, H. floridensis sp. n., was described from many locations in Florida, USA. It was separated from other representatives of the genus Hoplolaimus by its morphological and molecular characteristics. Maps with geographical distribution of several lance nematode species in North America were reconstructed based on published and original molecular identification of samples. Full article

Pine wilt disease, a devastating disease severely impacting pine ecosystems, is caused by the pinewood nematode Bursaphelenchus xylophilus (Steiner & Bührer, 1934) Nickle, 1970 (Nematoda: Parasitaphelenchidae). Controlling B. xylophilus is crucial for preventing and managing pine wilt disease. Recently discovered novel nematocidal lectins could provide more advantageous materials for utilizing genetically engineered bacteria to control this pathogen. Therefore, this study focuses on identifying novel nematocidal toxins within B. xylophilus lectins. Overall, we obtained twenty-one galectin, one L-type lectin (LTL), and three chitin-binding domain (CBD) genes by screening the B. xylophilus genome database; these genes were successfully expressed proteins. The bioassay results indicated that Bxgalectin2, Bxgalectin3, Bxgalectin4, Bxgalectin9, and BxLTL1 induced mortality rates exceeding 50% in B. xylophilus. Notably, Bxgalectin4 showed the strongest nematocidal activity, causing 88% mortality in the treated nematode population. The enzyme-linked immunosorbent assays further demonstrated that Bxgalectin3 (K_d = 8.992 nM) and Bxgalectin4 (K_d = 9.634 nM) had a higher binding affinity to GPI-anchored proteins from B. xylophilus. Additionally, Bxgalectin2 (K_d = 16.50 nM), Bxgalectin9 (K_d = 16.48 nM), and BxLTL1 (K_d = 24.34 nM) can bind to the GPI-anchored protein. This study reports, for the first time, that lectins endogenous to B. xylophilus exhibit nematocidal activity against their own species. These findings open up the possibility of using nematode lectins as potent control agents in the biological control of B. xylophilus. Full article

Horizontal gene transfer (HGT), the non-Mendelian transfer of genetic material between organisms, is relatively frequent in prokaryotes, whereas its extent among eukaryotes remains unclear. Here, we raise the hypothesis of a possible cross-phylum HGT event involving 5S ribosomal DNA (rDNA). A specific type of 5S rDNA sequence from the anuran Xenopus laevis was highly similar to a 5S rDNA sequence of the genome of its flatworm parasite Protopolystoma xenopodis. A maximum likelihood analysis revealed phylogenetic incongruence between the gene tree and the species trees, as the 5S rDNA sequence from Pr. xenopodis was grouped along with the sequences from the anurans. Sequence divergence analyses of the gene region and non-transcribed spacer also agree with an HGT event from Xenopus to Pr. xenopodis. Additionally, we examined whether contamination of the Pr. xenopodis genome assembly with frog DNA could explain our findings but found no evidence to support this hypothesis. These findings highlight the possible contribution of HGT to the high diversity observed in the 5S rDNA family. Full article

The cosmopolitan nematode Spirinia parasitifera has long been considered a single, morphologically variable species; however, mounting molecular evidence suggests that it represents a complex of cryptic taxa. In this study, we describe Spirinia koreana sp. nov., a new species collected from intertidal sediments of the Republic of Korea. The new species exhibits a high degree of morphological resemblance to both S. antipodea and S. parasitifera, with overlapping ranges in most morphological traits. While certain measurements, such as relatively shorter body length, more slender form (higher a ratio), moderately long tail length, and shorter spicule length differ from those in some described populations, no single morphological character alone reliably separates S. koreana from all previously reported specimens of S. parasitifera or S. antipodea. Nevertheless, molecular evidence from multiple genetic markers clearly supports its distinction as a separate species. Molecular data from mitochondrial COI, 18S rRNA, and 28S rRNA genes confirm the genetic distinctness of the Korean specimens from S. parasitifera and S. antipodea. Notably, S. koreana sp. nov. differs from other Spirinia species by 2.1–3.4% in 18S and up to 34.4% in 28S sequences, surpassing thresholds previously used to delimit marine nematode species. Our results emphasize the value of integrative taxonomy combining fine-scale morphology and multi-marker molecular data to uncover hidden diversity in meiofaunal nematodes. Full article

This study aimed to explore and identify soil-dwelling nematophagous fungi (NF) from the “El Texcal” Ecological Reserve in Morelos, Mexico, and evaluate their potential as biological control agents against Haemonchus contortus infective larvae (HcL3), a major parasitic threat in livestock systems. The fungi were isolated from soil using the sprinkling of soil on water agar plates. The identification of NF was achieved using morphological identification keys, which was corroborated by molecular procedures using the PCR technique in the ITS4 and ITS5 regions. The nematocidal effects occasioned by these NF were examined through their predatory activity (PA) against HcL3 on water agar plates, and additionally, the larval mortality attributed to their liquid filtrates (LFs) was assessed at three different concentrations (25, 50, and 100 mg/mL) on 96-well microtiter plates. Two NF were identified and classified as two species of Dactylellina genus, namely D. haptospora (Dh) and D. phymatopaga (Dp). The PA exhibited by these NF were 94.79% for Dh and 68.88% for Dp; while their LFs showed 27.83% mortality for Dh and 32.86% for Dp at the highest concentration assessed. While the PA was notably high, the moderate larvicidal effect of the LF suggests that their efficacy may primarily rely on direct physical interaction rather than metabolite-mediated toxicity. The high PA demonstrated by these two isolates of NF indicates that they could be effective candidates for biological control agents against HcL3. Full article

This paper presents an analysis of helminth diversity in reptiles in eight provinces of the Middle Volga region (European Russia) based on the dataset recently published in the GBIF as the Darwin Core Archive. The dataset contains up-to-date information on the occurrence of parasitic worms in lizards and snakes and summarizes the records obtained during long-term helminthological studies conducted in 1996–2024. It includes 8576 helminth occurrence records in nine reptile species inhabiting the Middle Volga region. All helminth occurrence records are georeferenced. In total, we present data on 45 parasitic worm species, including 4 species of cestodes, 21 species of trematodes, 16 species of nematodes, and 4 species of acanthocephalans. The richest helminth fauna was found in Natrix natrix (26 species), Lacerta agilis (21), Natrix tessellata (16), and Vipera berus (15). Less diverse is the helminth fauna in Anguis colchica (8 species), Zootoca vivipara (7), Vipera renardi (6), Coronella austriaca (5), and Eremias arguta (3). The diversity of helminths in reptiles of the Middle Volga region does not reach its maximum compared to other European countries. Most helminth species found in lizards and snakes of the studied region belong to the Palearctic faunal complex (25 species). Eight species of parasites have a Holarctic distribution. Seven helminth species parasitize reptiles only in Europe. Five species of parasites are cosmopolitan. Of the 45 species of helminths found in reptiles, 3 species have medical and veterinary significance as causative agents of dangerous helminthiasis. Data on the diversity and distribution of parasitic worms in reptiles of the Middle Volga region remain incomplete, so further observations may provide new occurrence records of helminths and expand the knowledge about their hosts. Full article