Search Results (105)

Rhabditis (Rhabditella) axei is a predominantly free-living nematode commonly found in sewage systems and decomposing organic matter. While primarily saprophytic, it has been documented as an opportunistic pathogen in human urinary and gastrointestinal tracts. The Chinese red panda (Ailurus styani), a rare and protected species in China, has not previously been reported as a host for Rhabditis (Rhabditella) spp. infections. This study reports the first documented occurrence of R. axei in red panda feces, unambiguously confirmed through integrative taxonomic approaches combining morphological and molecular analyses. The nematodes exhibited key morphological features consistent with R. axei, including a cylindrical rhabditiform esophagus, sexually dimorphic tail structures, and diagnostic spicule morphology. Molecular analysis based on 18S-ITS-28S rDNA sequencing confirmed their identity, showing >99% sequence similarity to R. axei reference strains (GenBank: PP135624.1, PP135622.1). Phylogenetic reconstruction using 18S rDNA and ITS rDNA sequences placed the isolate within a well-supported R. axei clade, clearly distinguishing it from related species such as R. blumi and R. brassicae. The findings demonstrate the ecological plasticity of R. axei as a facultative parasite capable of infecting non-traditional hosts and further highlight potential zoonotic risks associated with environmental exposure in captive wildlife populations. Our results emphasize the indispensable role of molecular diagnostics in accurately distinguishing morphologically similar nematodes within the Rhabditidae family, while providing essential baseline data for health monitoring in both in situ and ex situ conservation programs for this endangered species. Full article

Radopholus similus, commonly known as the burrowing nematode, is one of the major pathogens affecting banana production. Currently, the control of this pathogen relies on chemicals, as no resistant varieties are available. However, new control methods, such the application of ensilage biostimulants (EBs) near the banana rhizosphere, have shown effectiveness. Nevertheless, the impact of this organic control method on soil nematodes and other microbial components remains unknown. This study evaluates the effects of EB application on the native nematofauna of banana. EBs altered the flow of carbon, nutrients, and energy in ways that influenced the abundance of fungivorous and bacterivorous taxa, while consistently reducing the number of plant-parasitic nematodes throughout the experimental period. Specifically, EB application in the soil increased the abundance of certain free-living nematodes, including Aphelenchus, Aphelenchoides, Cephalobidae, and Rhabditidae, while decreasing both the abundance and diversity of phytoparasitic nematodes. In contrast, Criconematidae, Hoplolaimidae, Meloidogyne, Tylenchidae, and R. similis were more abundant in the control and oxamyl-treated soils. EBs can play a crucial role in strategies aimed to improve soil resilience, fertility, and natural suppression, provided that more sustainable production practices are adopted. Full article

This study investigates the impact of golden moles (Amblysomus sp.) on the abundance, diversity, and community structure of nematodes in kweek grass (Cynodon dactylon) within the Sovenga Hills of Limpopo Province, South Africa. Eight sites were sampled: four with active moles (sites: M1–M4), and four without (sites: T1–T4). Eighty soil samples were collected, and nematodes were extracted. A total of 23 nematode genera were identified, including 3 plant-parasitic and 20 free-living genera. The frequency of occurrence (FO) data showed that Aphelenchus sp. and Acrobeles sp. were the most prevalent nematodes, each occurring in 87.5% of the samples. In contrast, Eucephalobus sp., Tripylina sp., Discolaimus sp., and Tylenchus sp. had the lowest FO, appearing in only 12.5% of samples. The diversity indices (the Shannon index, the maturity index, and the plant-parasitic index) showed significant differences between the two environments. The Shannon index (H′) and maturity index were the most effective indicators of ecosystem disturbance. The lowest H′ was found at T4 (1.7 ± 0.2), compared with a higher value at M1 (2.4 ± 0.1). The principal component analysis (PCA) results revealed a positive correlation between Ditylenchus and the clay in the soil. In addition, Cervidellus was associated with soil pH. Network analysis revealed increased complexity in the nematode community structure at mole-affected sites. These findings suggest that mole activity alters soil properties and indirectly affects nematode diversity and trophic structure. Full article

Protecting the soil ecosystem’s functioning is one of the main goals of recent regulations of chemicals. It is important to take soil biodiversity into account when designing cropping systems and measuring their impacts. Our main objective was to evaluate the effects of an organic amendment on soil nematode biodiversity compared to two years of fumigation. The plot-trial was conducted on tomato and lettuce plants under greenhouse, and free-living nematodes were used as bio-indicators of soil health. Treatments included a soil fumigant (applied once or twice over time), water control, and an organic substance. Soil samplings were carried out to determine the Meloidogyne incognita reproduction factor and the soil nematode community analysis using soil biological indicators. Data showed that soil fumigation clearly made the soil increasingly dependent on chemicals. Furthermore, fumigants suppressed pests and pathogens as well as their natural antagonists, causing a lack of biodiversity. While soils treated with organic matter respond slowly to stressors, they are progressively more suppressive thanks to biodiversity enrichment. Nematodes have proven to be useful indicators of the soil biota in response to biotic or abiotic disturbances. Their species richness and functional diversity make them valid bioindicators of soil management impact. Full article

Significant models predicting Soil Organic Carbon (SOC) and other chemical and biological indicators of soil health in an experimental farm with semi-arid Mediterranean Calcisol have been obtained by partial least squares (PLS) regression, with mid-infrared (MIR) spectra of whole soil samples used as independent variables (IVs). The dependent variables (DVs) included SOC, pH, electric conductivity, N, P₂O₅, K, Ca²⁺, Mg²⁺, Na⁺, Fe, Mn, Cu and Zn. The DVs also included free-living nematodes and microbivores, such as Rhabditids and Cephalobids, and phytoparasitics, such as Xiphinema spp. and other Dorylaimids. More importantly, an attempt was made to determine which spectral patterns allowed each dependent variable (DV) to be predicted. For this purpose, a number of statistical indices were plotted between 4000 and 450 cm⁻¹, e.g., variable importance for prediction (VIP) and beta coefficients from PLS, loading factors from principal component analysis (PCA) and correlation and determination indices. The most effective plots, however, were the “scaled subtraction spectra” (SSS) obtained by subtracting the averages of groups of spectra in order to reproduce the spectral patterns typical in soils where the values of each DV are higher, or vice versa. For instance, distinct SSS resembled the spectra of carbonate, clay, oxides and SOC, whose varying concentrations enabled the prediction of the different DVs. Full article

Soil-transmitted helminths (STHs) are parasitic nematodes that infect humans, particularly in tropical and subtropical regions, where they contribute substantially to neglected tropical diseases (NTDs). Among them, hookworms (Ancylostoma duodenale, Necator americanus and Ancylostoma ceylanicum) cause substantial morbidity, leading to anaemia, malnutrition, and developmental impairment. Despite the global impact of hookworm disease, genomic research on A. duodenale has lagged behind that of other hookworms, limiting comparative and molecular biological investigations. Here, we report the first chromosome-level reference genome of A. duodenale, assembled from a single adult specimen archived in ethanol at −20 °C for more than 27 years. Using third-generation sequencing (PacBio Revio, Menlo Park, CA, USA, Oxford Nanopore, Oxford, UK), Hi-C scaffolding, and advanced computational tools, we produced a high-quality 319 Mb genome, filling a critical gap in hookworm genomics. Comparative analyses with N. americanus and the related, free-living nematode Caenorhabditis elegans provided new insights into genome organisation, synteny, and specific adaptations. While A. duodenale exhibited strong chromosomal synteny with N. americanus, its limited synteny with C. elegans highlights its distinct parasitic adaptations. We identified 20,015 protein-coding genes, including conserved single-copy orthologues (SCOs) linked to host–pathogen interactions, immune evasion and essential biological processes. The first comprehensive secretome analysis of A. duodenale revealed a diverse repertoire of excretory/secretory (ES) proteins, including immunomodulatory candidates predicted to interact with host structural and immune-related proteins. This study advances hookworm genomics, establishes a basis for the sequencing of archival specimens, and provides fundamental insights into the molecular biology of A. duodenale. The genomic resource for this hookworm species creates new opportunities for diagnostic, therapeutic, and vaccine development within a One Health framework. It complements recent epidemiological work and aligns with the WHO NTD roadmap (2021–2030) and Sustainable Development Goal 3.3. Full article

Two new species from the Yellow Sea, Hypodontolaimus minus sp. nov. and Bolbolaimus distalamphidus sp. nov., are described in this study. Hypodontolaimus minus sp. nov. is characterized by a relatively small body length, a cuticle with two longitudinal lateral differentiations connected with transverse bars, four files of sublateral somatic setae, a pharynx with an anterior and posterior bulb, L-shaped spicules, a slightly swollen proximal end, a distal end tapered with a posterior pointed hook, and a gubernaculum with dorsal caudal apophysis. Bolbolaimus distalamphidus sp. nov. is characterized by a relatively small body size, a strongly annulated cuticle, six short outer labial sensilla and four long cephalic setae, an amphideal fovea unispiral oval that is far from the anterior end, slightly curved spicules, gubernaculum with anterior-pointed apophysis, and a conical tail. Phylogenetic analyses within the family Chromadoridae and the superfamily Microlaimoidea based on combined rDNA sequences confirmed the placement of Hypodontolaimus minus sp. nov. and Bolbolaimus distalamphidus sp. nov. The subfamily of Chromadorinae is shown as a monophyletic clade, the genera of subfamily Hypodontolaiminae are shown as a paraphyletic group, and the genus of Ptycholaimellus shows high intraspecific diversity. The placement of genera Aponema and Molgolaimus within the superfamily Microlaimoidea is discussed based on combined rDNA sequences. Full article

Detecting microplastics (MPs) in marine organisms is vital for understanding the ecological impact of MP pollution. Free-living marine nematodes, key players in benthic ecosystems, are often employed as bioindicators because of their sensitivity to environmental changes and thus hold promise as bioindicators for MP pollution too. This study investigated the detection of MPs in nematodes using µ-Raman spectroscopy combined with a tailored digestion protocol, targeting MPs in size ranges between 1 and 15 µm. While this is the first documented attempt to detect MPs in field-collected nematodes, significant challenges were identified. Contamination, particularly from airborne MPs and plastic-based laboratory materials, posed a major obstacle. We found higher numbers of <5 µm particles of polypropylene (PP), polyethylene terephthalate (PET), polylactic acid (PLA), polymethyl methacrylate (PMMA), and polystyrene (PS) in a natural community of nematodes compared to blank controls, suggesting the potential ingestion of small-sized MPs by nematodes in the real world. However, small MPs exhibited greater contamination challenges, underscoring the need for improved contamination control measures, such as open-air filters and plastic-free workflows. Despite these challenges, this study highlights the potential of µ-Raman spectroscopy as a valuable tool for detecting small-sized MPs in field-collected marine invertebrates, provided contamination risks are minimized. The likelihood of nematodes encountering MPs in marine sediments is high, but whether this translates to significant ingestion remains uncertain pending on the analysis of more field samples and the application of efficient measures of contamination reduction. Full article

Faecal parasitological examination of three red kangaroos (Osphranter rufus) newly arrived at Sofia Zoo, Bulgaria, revealed infestation with nematode eggs. The animals were successfully treated with albendazole and ivermectin. Adult nematodes obtained after deworming the kangaroos were identified as gastric strongylids of the species Rugopharynx australis (Mönnig, 1926). The initially collected faecal samples were used to follow the development of the parasites, in particular, the viability of the larvae hatching from the eggs. Morphometric and molecular data as well as some epidemiological observations of the species in the present materials are provided. The study provides the first morphological description of the free-living, infective third-stage larvae of the species. It is also the first record of R. australis in captive-bred kangaroos on the European continent. Full article

Background: Human central nervous system infections due to free-living nematodes, although extremely rare, are usually fatal. Immunodeficiency has not been a feature of most of these cases, unlike the situation pertaining to disseminated Strongyloides stercoralis infection. Case report: An elderly immunocompetent man presented with a history of tinnitus and otalgia, progressing to central nervous system involvement with confusion, weakness, and other neurological signs. Examination revealed a unilateral external auditory canal soft tissue mass and radiological evidence of ipsilateral temporal bone destruction and brain parenchymal disease. A biopsy of the ear canal mass revealed the presence of an unidentified nematode species, and treatment with anthelminthics was started. The patient’s clinical condition deteriorated and he died shortly after admission to the intensive care unit. The immediate cause of death was bronchopneumonia. During the autopsy, an extensive involvement of the right middle cranial fossa was found, with destruction of the squamous and petrous parts of the temporal bone. Results: We identified adult, larval, and egg stages of a free-living nematode in the antemortem external auditory canal tissue mass and the post-mortem brain samples. Polymerase chain reaction assays, with Sanger and whole-genome sequencing, identified Cephalobus cubaensis. This is a free-living species not previously known to be pathogenic to humans, although nematodes of the same genus have caused mastitis in horses. Conclusions: Microscopic appearance and the invasive behaviour of the pathogen evoked a putative diagnosis of Halicephalobus gingivalis, the most frequently reported free-living nematode infecting humans. However, this nematode’s size and anatomical features, and the clinical presentation and duration of illness, prompted the consideration of an alternative species. We speculate that an initial bacterial otitis externa provided the opportunity for colonization by the nematode from an environmental source and subsequent invasion. Full article

We report the discovery of a novel free-living marine nematode, Dracognomus elongatus sp. nov., from the genus Dracognomus Allen & Noffsinger, 1978 (Nematoda: Draconematidae), collected from geniculate coralline algal assemblages in the intertidal zone along the eastern coast of Korea in the Northwest Pacific Ocean. Dracognomus elongatus sp. nov. is distinguished from its congeners by several key features: a relatively long body length (522 µm), densely developed minute spine-like ornamentation along the margins of body annules, small pore-shaped amphids (2 µm) with membranous tubes filled with corpus gelatum extending to the fifth body annule, twelve modified cephalic adhesion tubes located posterior to the rostrum, eight pairs of modified adhesion tubes in the mid-body region, an arrangement of both normal and modified subventral adhesion tubes (three pairs of each), disc-shaped tips on sublateral adhesion tubes, absence of copulatory thorns in males, and the presence of three pairs of short setae with no protuberances on the non-annulated tail end. Morphological details and illustrations were obtained using differential interference contrast microscopy. We also provide information on the geographic distribution and comparative characteristics of species within the genus Dracognomus, along with a schematic ventral view of a congener illustrating the arrangement of posterior adhesion tubes and copulatory thorns. Additionally, we present a species-level pictorial dichotomous key. Dracognomus elongatus sp. nov. is the eighth described species of this rare genus and marks the first record of Dracognomus in the Northwest Pacific Ocean. Full article

This study provides a taxonomic analysis of three newly discovered species of free-living marine nematodes in the subgenus Tricoma from the East Sea, Korea. Tricoma (Tricoma) polyringulata sp. nov. is characterized by its relatively small body size, with lengths of 280–370 µm in males and 320–390 µm in females, and 75–89 main rings. Diagnostic features include an uncovered first ring, triangular head shape, amphidial fovea with slight constriction, and a unique pattern of somatic setae, comprising 7–9 subdorsal and 8–12 subventral setae. Tricoma (Tricoma) fortiseta sp. nov. is distinguished by 65–69 main rings, 10–12 subdorsal setae, and 17–20 subventral setae, along with a hexagonal head, a well-defined labial region with six lips, and bifid-tipped cephalic setae located medially on the head. Tricoma (Tricoma) uljinensis sp. nov. exhibits 67–70 main rings, with a thick, sclerotized head that is 1.5 times as wide as its length, gently triangular in shape. Its diagnostic features include a gubernaculum bent downward near its midpoint and a conical terminal ring, with 25–39% of the desmos covered. Detailed morphological descriptions of each species are provided, along with a comparative table of morphological traits for species with 61–75 main rings and an illustrated key for identification. Full article

Agricultural soil environments contain different types of nematodes in all trophic levels that aid in balancing the soil food web. Beneficial free-living nematodes (FLNs) consist of bacterivores, fungivores, predators, and omnivores that help in the mineralization of the soil and the top-down control of harmful plant-parasitic nematodes (PPNs). Annually, USD 125 billion in worldwide crop losses are caused by PPNs, making them a plant pathogen of great concern for growers. Farmers have started to implement the use of cover crops in agricultural systems for the protection and enrichment of soil but research on how different cover crops affect nematode populations is lacking and in demand. This study aims to determine the effects of legume and grass cover crops, Cowpea (Vigna unguiculata) and Pearl Millet (Pennisetum glaucum), as well as their mixture on the abundance and diversity of FLN and PPN populations. Soil samples were collected at the time of cover crop maturity and spinach harvest to analyze nematode communities using both morphological and DNA metabarcoding analysis. The results showed that the application of Cowpea and Pearl Millet as well as their mixture in a spinach agricultural system led to the control of PPNs and proliferation of FLN communities, with each cover crop treatment demonstrating different advantages for the various nematode feeding groups. Soil property analysis did not show a significant difference except for magnesium and total nitrogen levels, which were significantly correlated with nematode community composition. The overall findings of our study indicate that the choice of cover crop implementation by growers for spinach cultivation should be based on specific soil health conditions, which in turn promote soil fertility and a healthy nematode community. Full article

We examined the taxonomical and functional traits of free-living nematodes, focusing on their density by genus, maturity index (MI), and trophic diversity index (ITD) to determine whether these indices are sensitive to changes in the organic content of the sediment. Samples were collected in autumn and spring from 12 subtidal sampling stations in Rocha Lagoon, distributed between the outer (near the mouth) and the inner sector. We identified 26 genera, with higher abundance in the inner sector, likely due to increased organic matter and biopolymers. In spring, both sectors had sediments rich in fresh organic matter, dominated by deposit-feeding nematodes and showing low trophic diversity (high ITD values). In autumn, the inner sector maintained similar characteristics to spring sampling, while the outer one was dominated by older organic matter, predatory nematodes and higher trophic diversity. The MI showed low variation between sectors, suggesting a disturbed environment. Our findings support the use of ITD to assess other aspects of communities such as the response of trophic groups to the freshness of organic matter, while the MI seems less effective for assessing the ecological status of Rocha Lagoon. Understanding nematode biodiversity and functional traits is crucial for effective ecological quality assessments. Full article

A study was conducted in the mountains of Magoebaskloof, Limpopo Province, where oak trees grow along the banks of the Broederstroom River. This study revealed that 22 nematode genera were associated with oak trees (Quercus robur). The most frequently occurring nematodes were Aphelenchus sp. (100%) and Plectus sp. (100%), followed by Helicotylenchus sp. (90%). This study examined the relationship between nematodes and the physicochemical properties of the soil using Pearson correlation. It uncovered that the organic matter content (OMC) had a negative correlation with the number of Panagrolaimus sp. (r = −0.770) and Hemicycliophora sp. (r = −0.674). Conversely, the sand percentage positively correlated (r = 0.695) with the number of Hemicycliophora sp. The clay content of the soil showed a positive correlation (r = 0.617) with the number of Ditylenchus. Soil pH demonstrated a significant negative correlation with Acrobeloides sp. (r = −0.877). The canonical correspondence analysis (CCA) explained 63.3% of the relationship between nematodes and soil physicochemical properties. The CCA results indicated that Ditylenchus exhibited a positive correlation with OMC, while the Panagrolaimus and Hemicycliophora species showed a negative correlation with OMC. The results indicated that none of the soil sample sites were under stress. The soil food web analysis revealed that most soil samples were nutrient-enriched with a low C/N ratio. In conclusion, this study revealed that oak trees harbor a high diversity of plant-parasitic and free-living nematodes. The results suggest that soil nematodes, particularly free-living bacterivores, such as Panagrolaimus, can indicate organic matter content in the soil. Full article