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Abstract Background The infraorder Rhigonematomorpha comprises a group of obligate parasitic nematodes of millipedes (Arthropoda: Diplopoda). The current species identification of Rhigonematomorpha nematodes remains mainly based on morphological features, with molecular-based identification still in its infancy. Also, current knowledge of the phylogeny of Rhigonematomorpha is far from comprehensive. Methods The morphology of Rhigonematomorpha nematodes belonging to the genus Rhigonema, collected from the millipede Spirobolus bungii Brandt (Diplopoda: Spirobolida) in China, was studied in detail using light and scanning electron microscopy. Five different genetic markers, including the nuclear small ribosomal subunit (18S), internal transcribed spacer (ITS) and large ribosomal subunit (28S) regions and the mitochondrial cox1 and cox2 genes of these Rhigonematomorpha nematodes collected from China and Rhigonema naylae collected from Japan were sequenced and analyzed using Bayesian inference (BI) and Assemble Species by Automatic Partitioning (ASAP) methods. Phylogenetic analyses that included the most comprehensive taxa sampling of Rhigonematomorpha to date were also performed based on the 18S + 28S genes using maximum likelihood (ML) and BI methods. Results The specimens of Rhigonema collected from S. bungii in China were identified as a new species, Rhigonema sinense n. sp. Striking variability in tail morphology was observed among individuals of R. sinense n. sp. ASAP analyses based on the 28S, ITS, cox1 and cox2 sequences supported the species partition of R. sinense n. sp. and R. naylae, but showed no evidence that the different morphotypes of R. sinense n. sp. represent distinct genetic lineages. BI analyses also indicated that R. sinense n. sp. represents a separated species from R. naylae based on the cox1 and cox2 genes, but showed that R. naylae nested in samples of R. sinense n. sp. based on the ITS and 28S data. Phylogenetic results showed that the representatives of Rhigonematomorpha formed two large clades. The monophyly of the families Carnoyidae and Ichthyocephalidae and the genus Rhigonema was rejected. The representatives of the family Ransomnematidae clustered together with the family Hethidae with strong support. Conclusions A new species of Rhigonematomorpha, R. sinense n. sp. is described based on morphological and molecular evidence. ASAP analyses using 28S, ITS, cox1 and cox2 data indicate the striking variability in tail morphology of R. sinense n. sp. as intraspecific variation, and also suggest that partial 28S, ITS, cox1 and cox2 markers are effective for molecular identification of Rhigonematomorpha nematodes. The phylogenetic results support the traditional classification of Rhigonematomorpha into the two superfamilies Rhigonematoidea and Ransomnematoidea, and indicate that the families Carnoyidae and Ichthyocephalidae and the genus Rhigonema are non-monophyletic. The present phylogeny strongly supports resurrection of the family Brumptaemiliidae, and also indicates that the family Ransomnematidae is sister to the family Hethidae. Graphical Abstract

Polycyclic aromatic hydrocarbons (PAHs) are an important group of organic pollutants present in all parts of the environment, affecting ecosystems and human health. PAHs, which have a strong affinity for organic carbon, are found in large quantities in soil, which is one of the most important sinks for these contaminants. Their impact on the soil biotic compartments depends on a number of different factors in combination with PAH behaviour and can be assessed using soil monitoring. Soil fauna have already shown excellent properties for biomonitoring of contaminants with most promising indicator frameworks based on nematodes, which are involved in essential processes in this environment. Nematodes respond to PAHs at multiple levels, including molecular, individual and community levels. At the molecular level, this is associated with activation of metabolic pathways for xenobiotics and increased demand for energy and resources. At the individual level, this is reflected in the slowing down of various physiological processes, which has consequences at the individual and community level for sensitive taxa. In this review, the toxicity and the direct and indirect effects of PAHs on soil nematode communities are discussed. It also considers the perspectives and challenges in assessing the toxicity of PAHs and their indication using soil nematodes.

Nutria (or coypu, Myocastor coypus), is a semi-aquatic rodent that is native to South America and has been introduced almost all over the world since the end of the 19th century. In Europe, this rodent is considered an invasive species. In this report, we analyzed nutria fecal samples in a small coastal wetland of Central Italy, using different techniques (fresh smear, direct immunofluorescence, Baermann technique, flotation, ethyl acetate sedimentation) to obtain an arrangement of eukaryote endoparasites (Protozoa and Helminths) and compare them with data available in the literature for both Italy and worldwide. We recorded five taxa, with a dominant occurrence (>70%) of nematodes of the genus Strongyloides. Moreover, we reported for the first time in nutria a bronchopulmonary strongyle nematode (Muellerius vel. Angiostrongylus) and, for the first time in Italy, protozoans of the genus Cryptosporidium. Since nutria co-occurs with humans and domestic animals in the study area, we highlighted possible sanitary and management implications. [ABSTRACT FROM AUTHOR]

Biodiversity surveys of Arctic soil ecosystems are limited. Here, we provide a sequence-based inventory of soil fauna from an Arctic tundra ecosystem near the Canadian High Arctic Research Station in Cambridge Bay, Nunavut. Invertebrate communities were extracted at a vegetated and non-vegetated site in three replicates and inventoried using 18S metabarcode sequencing. A total of 361 amplicon sequence variants (ASV) were identified and assigned to the closest matching taxonomic orders, most of which belonged to the Nematoda and Arthropoda. Vegetated soils showed no significantly higher ASV richness relative to non-vegetated soils although they contained a significantly higher diversity of arthropod taxa including insects, mites, and springtails. Most taxa were found only at a single location and even samples from the same site displayed distinct communities, suggesting that belowground species richness in Arctic tundra habitats is highly heterogeneous. Preserving soil biodiversity in a changing Arctic is essential for Inuit communities who rely on intact tundra ecosystems for their health and wellbeing. [ABSTRACT FROM AUTHOR]

Fire is a common disturbance in many biomes, with both beneficial and detrimental effects on soil biology, which largely depend on fire intensity. However, little is known about the impact of fire on soil nematode communities in terrestrial ecosystem. In the present study, we investigated the effects of short‐term prescribed fire on soil nematode communities and soil properties in an old‐field grassland in Northern China. The results showed that burning significantly increased soil nematode abundance by 77% and genus richness by 49% compared to the control. Burning also decreased taxon dominance by 45% (Simpson's D) and increased nematode diversity by 31% (Shannon‐Weaver H'). However, burning increased plant parasites (particularly genera Cephalenchus and Pratylenchus) and shifted community to more bacterial‐feeding genera (i.e., decreased Channel Index). Generally, burning increased soil bio‐available nitrogen (NH4+–N and NO3−–N) content, which would be the main drivers causing nematode community to flourish via a "bottom‐up" effect. These results suggest that prescribed fire increases nematode diversity and alters community composition toward more plant parasites and bacterial feeders. Our findings highlight the importance of prescribed fire management in shaping short‐term nematode community structure and function, but the long‐term effects and impacts of these changes on soil nutrient and carbon cycling remain unknown. [ABSTRACT FROM AUTHOR]

Uncovering drivers of community assembly is a key aspect of learning how biological communities function. Drivers of community similarity can be especially useful in this task as they affect assemblage‐level changes that lead to differences in species diversity between habitats. Concepts of β‐diversity originally developed for use in free‐living communities have been widely applied to parasite communities to gain insight into how infection risk changes with local conditions by comparing parasite communities across abiotic and biotic gradients.Factors shaping β‐diversity in communities of immature parasites, such as larvae, are largely unknown. This is a key knowledge gap as larvae are frequently the infective life‐stage and understanding variation in these larval communities is thus key for disease prevention. Our goal was to uncover links between β‐diversity of parasite communities at different life stages; therefore, we used gastrointestinal nematodes infecting African buffalo in Kruger National Park, South Africa, to investigate within‐host and extra‐host drivers of adult and larval parasite community similarity.We employed a cross‐sectional approach using PERMANOVA that examined each worm community at a single time point to assess independent drivers of β‐diversity in larvae and adults as well as a longitudinal approach with path analysis where adult and larval communities from the same host were compared to better link drivers of β‐diversity between these two life stages.Using the cross‐sectional approach, we generally found that intrinsic, within‐host traits had significant effects on β‐diversity of adult nematode communities, while extrinsic, extra‐host variables had significant effects on β‐diversity of larval nematode communities. However, the longitudinal approach provided evidence that intrinsic, within‐host factors affected the larval community indirectly via the adult community.Our results provide key data for the comparison of community‐level processes where adult and immature stages inhabit vastly different habitats (i.e. within‐host vs. abiotic environment). In the context of parasitism, this helps elucidate host infection risk via larval stages and the drivers that shape persistence of adult parasite assemblages, both of which are useful for predicting and preventing infectious disease. [ABSTRACT FROM AUTHOR]

Little is known about the taxonomy of deep-sea nematode species inhabiting cold seep habitats. An opportunity to characterize the nematode species communities of New Zealand cold seeps was provided by a 2019 research voyage to New Zealand’s Hikurangi Margin, during which macrofauna cores were obtained at two seeps at approximately 1,250 and 2,000 m water depth. Here, six new species of the order Enoplida are described. Metacylicolaimus catherinae sp. nov. represents the first record of the genus for the New Zealand Exclusive Economic Zone and for the deep sea globally. Halalaimus talaurinus sp. nov., Thalassoalaimus duoporus sp. nov. and Crenopharynx crassipapilla sp. nov. are only the second species of their respective genera to be described/recorded from New Zealand waters, and Oncholaimus adustus sp. nov. is the eighth species of the genus to be recorded from the region. Rhabdodemania zealandiaensis sp. nov. was among the most abundant and widespread species found at the Hikurangi Margin seep sites. A few specimens had been found in a previous ecological study of meiofaunal nematode communities on Chatham Rise, a submarine ridge south of Hikurangi Margin. It is possible that this species has a preference for seep environments due to elevated food availability, however it does not seem to be exclusively found in seeps. We find no evidence for an affinity between nematode seep communities in New Zealand and elsewhere, which is consistent with the high variability in nematode community observed to date among regions. Ongoing work on the ecology and distribution of nematode communities at the Hikurangi Margin seep sites will help determine spatial patterns in abundance and species distributions in more detail, including the identification of any species/taxa with affinities with seeps. [ABSTRACT FROM AUTHOR]

Organisms utilize chemical signals to perceive their external environmental and regulate their behavior and development. The discovery of ascarosides; a class of small molecular compounds, has been a breakthrough in the study of nematode pheromones. Ascarosides are structurally and functionally diverse and occur widely in nematodes. They regulate a variety of behaviors, including mating, diapause, foraging, aggregation, and dispersal. This paper primarily summarizes the structure, function, biosynthesis, metabolism and signal transmission of ascarosides, thereby providing a reference for future research on chemical signal regulation theory, multi-species interactions, and the development of novel targeted drugs. [ABSTRACT FROM AUTHOR]

El pez conejo Lagocephalus laevigatus registra diez especies de helmintos de las cuales nueve no han sido reportadas para la especie, lo cual los convierte en nuevos registros. Cestodos y trematodos registran los valores más altos de abundancia. Se reportan estadios larvales del género Nybelinia sp. y Scyphophyllidium sp. Bianium plicitum se vuelve a registrar en L. laevigatus. El nematodo Hysterothylacium aduncum presenta un alto nivel de individuos con bajos valores de prevalencia e intensidad media, mientras que Hysterothylacium sp. registra las prevalencias más altas. Las larvas de acantocéfalos (cistacantos) muestran niveles altos en prevalencia (45.16%). Este es el primer trabajo que reporta la helmintofauna de L. laevigatus en la localidad de Chachalacas y el Golfo de México.

Abstract The aim of this study was to register the first occurrence of Synhimantus (Dispharynx) nasuta (Nematoda: Acuariidae) in some species of wild birds in Brazil. In addition, the aim was to deepen the knowledge about the morphology of this species through analysis using scanning electron microscopy. Nematodes were collected in wild birds of the species Turdus leucomelas, T. rufiventris, Mimus saturninus, Pitangus sulphuratus, Megascops choliba, Tyto furcata, and Falco sparverius. The morphological and morphometric data observed in the nematodes prove that these parasites are S. (D.) nasuta. This study also provides morphological data from light microscopy and scanning electron microscopy (SEM), as well as the morphometry of this nematode in each host species. Therefore, the current study confirms the first record of this nematode in F. sparverius and T. furcata in South America and, at the same time, these findings expand the host range of this parasite species worldwide, through the first records in M. choliba, M. saturninus, T. leucomelas and T. rufiventris.

Benthic meiofauna is a fundamental component of food webs and nutrient exchange of marine ecosystems. However, its diversity pattern and ecology of intertidal meiofauna remain poorly understood because the studies are often constrained by morphology-based species identification. Environmental DNA metabarcoding is a powerful tool to overcome this limitation. In the present study, we assessed the intertidal meiofauna diversity and their correlations with environmental variables using eDNA metabarcoding approach with both 18S rRNA and two COI markers. The 18S rRNA marker suggested Nematoda (32.1%), Arthropoda (10.5%), and Cercozoa (8.0%) were the three most abundant phyla while COI primers show strong biased towards either Arthropoda or Nematoda and generated inconsistent results when using different reference databases. The correlation analysis showed that most examined environmental factors were strongly associated with community separation, but only salinity, the content of clay, and pheophorbide were found to be significant. The eDNA metabarcoding recovered a terrestrial nematode belonging to the genus Acrobeloides in a marine-related environment. Further resampling and laboratory experiments confirmed this species is tolerant to high salinity concentrations, suggesting eDNA metabarcoding recovery is consistent with the laboratory experiment. This result demonstrated eDNA metabarcoding can be a promising tool for high-throughput new habitat discovery in meiofauna.

Sentinel surveillance plays a critical role in monitoring pathogen circulation, assessing potential threats for species conservation, and evaluating the risk of spillover to human populations. This study provides a comprehensive exploration of helminth parasites in the Mediterranean-distributed hedgehog species Atelerix algirus in Mallorca, Balearic Islands. Using an integrated approach that combines necropsies and morphological and molecular identifications using the COI gene, we identified 11 helminth taxa in 135 hedgehogs, representing half of those that died at the local wildlife hospital in Mallorca between 2019 and 2022. We report an overall A. cantonensis prevalence of 11.5% and confirm the first case of a subclinical neuroangiostrongyliasis infection in a wildlife host. Infection prevalences over the year revealed that only two species, the nematode A. cantonensis and the cestode Mathevotaenia sp., had a seasonal pattern, with most A. cantonensis cases occurring in autumn and, to a lesser extent, Mathevotaenia sp. cases in winter. This pattern is probably due to the higher abundance and greater activity of snails and slugs (intermediate hosts) during these seasons, with important implications for public health and strategies for prevention of neuroangiostrongyliasis. Other key findings include a high prevalence (88.1%) of the lungworm Crenosoma striatum and detection of the acanthocephalan Moniliformis saudi for the first time in A. algirus. We anticipate that our study will facilitate surveillance efforts and clarify species identities in future studies. Given the lethal effects of A. cantonensis infection in hedgehogs, further studies are needed to evaluate the threat this parasite represents to European wildlife.

Entomopathogenic nematodes from the genus Steinernema are lethal insect parasites that quickly kill their insect hosts with the help of their symbiotic bacteria. Steinernema carpocapsae is one of the most studied entomopathogens due to its broad lethality to diverse insect species and its effective commercial use as a biological control agent for insect pests, as well as a genetic model for studying parasitism, pathogenesis, and symbiosis. In this study, we used long-reads from the Pacific Biosciences platform and BioNano Genomics Irys system to assemble the most complete genome of the S. carpocapsae ALL strain to date, comprising 84.5 Mb in 16 scaffolds, with an N50 of 7.36 Mb. The largest scaffold, with 20.9 Mb, was identified as chromosome X based on sex-specific genome sequencing. The high level of contiguity allowed us to characterize gene density, repeat content, and GC content. RNA-seq data from 17 developmental stages, spanning from embryo to adult, were used to predict 30,957 gene models. Using this improved genome, we performed a macrosyntenic analysis to Caenorhabditis elegans and Pristionchus pacificus and found S. carpocapsaes chromosome X to be primarily orthologous to C. elegans and P. pacificus chromosome II and IV. We also investigated the expansion of protein families and gene expression differences between adult male and female stage nematodes. This new genome and more accurate set of annotations provide a foundation for additional comparative genomic and gene expression studies within the Steinernema clade and across the Nematoda phylum.

Plants are exposed to cellular damage by mechanical stresses, herbivore feeding, or invading microbes. Primary wound responses are communicated to neighboring and distal tissues by mobile signals. In leaves, crushing of large cell populations activates a long-distance signal, causing jasmonate production in distal organs. This is mediated by a cation channel-mediated depolarization wave and is associated with cytosolic Ca2+ transient currents. Here, we report that much more restricted, single-cell wounding in roots by laser ablation elicits non-systemic, regional surface potential changes, calcium waves, and reactive oxygen species (ROS) production. Surprisingly, laser ablation does not induce a robust jasmonate response, but regionally activates ethylene production and ethylene-response markers. This ethylene activation depends on calcium channel activities distinct from those in leaves, as well as a specific set of NADPH oxidases. Intriguingly, nematode attack elicits very similar responses, including membrane depolarization and regional upregulation of ethylene markers. Moreover, ethylene signaling antagonizes nematode feeding, delaying initial syncytial-phase establishment. Regional signals caused by single-cell wounding thus appear to constitute a relevant root immune response against small invaders.

The root-knot nematode (RKN) species Meloidogyne incognita and M. javanica cause substantial root system damage and suppress yield of susceptible cowpea cultivars. The narrow-based genetic resistance conferred by the Rk gene, present in some commercial cultivars, is not effective against Rk-virulent populations found in several cowpea production areas. The dynamics of virulence within RKN populations require a broadening of the genetic base of resistance in elite cowpea cultivars. As part of this goal, F1 and F2 populations from the cross CB46-Null (susceptible) x FN-2-9-04 (resistant) were phenotyped for M. javanica induced root-galling (RG) and egg-mass production (EM) in controlled growth chamber and greenhouse infection assays. In addition, F[Formula: see text] families of the same cross were phenotyped for RG on field sites infested with Rk-avirulent M. incognita and M. javanica The response of F1 to RG and EM indicated that resistance to RKN in FN-2-9-04 is partially dominant, as supported by the degree of dominance in the F2 and F[Formula: see text] populations. Two QTL associated with both RG and EM resistance were detected on chromosomes Vu01 and Vu04. The QTL on Vu01 was most effective against aggressive M. javanica, whereas both QTL were effective against avirulent M. incognita Allelism tests with CB46 x FN-2-9-04 progeny indicated that these parents share the same RKN resistance locus on Vu04, but the strong, broad-based resistance in FN-2-9-04 is conferred by the additive effect of the novel resistance QTL on Vu01. This novel resistance in FN-2-9-04 is an important resource for broadening RKN resistance in elite cowpea cultivars.

Hunger affects the behavioral choices of all animals, and many chemosensory stimuli can be either attractive or repulsive depending on an animal's hunger state. Although hunger-induced behavioral changes are well documented, the molecular and cellular mechanisms by which hunger modulates neural circuit function to generate changes in chemosensory valence are poorly understood. Here, we use the CO2 response of the free-living nematode Caenorhabditis elegans to elucidate how hunger alters valence. We show that CO2 response valence shifts from aversion to attraction during starvation, a change that is mediated by two pairs of interneurons in the CO2 circuit, AIY and RIG. The transition from aversion to attraction is regulated by biogenic amine signaling. Dopamine promotes CO2 repulsion in well-fed animals, whereas octopamine promotes CO2 attraction in starved animals. Biogenic amines also regulate the temporal dynamics of the shift from aversion to attraction such that animals lacking octopamine show a delayed shift to attraction. Biogenic amine signaling regulates CO2 response valence by modulating the CO2-evoked activity of AIY and RIG. Our results illuminate a new role for biogenic amine signaling in regulating chemosensory valence as a function of hunger state.