Biodiversity and distribution of entomophilic nematodes in the Terai region of eastern Uttar Pradesh, India

Abstracts of the 16th Symposium of the Russian Society of Nematologists cover wide range of fundamental and applied nematological studies. These studies address nematode taxonomy, morphology and phylogeny, marine, freshwater and soil nematode biodiversity, deep-sea parasitism, and nematode–fungus–insect symbioses. Strong emphasis is placed on plant-parasitic and forest-pathogenic nematodes, including risks of pine wilt disease, vector relationships with bark beetles, host susceptibility of trees and crops, resistance screening, and nematicide application. Several works highlight invasive species impacts, soil ecosystem responses, and methodological advances in microbiome analysis. Overall, the symposium reflects active research on nematode ecology, evolution, and their significance for agriculture, forestry, and environmental monitoring.

Given the growing interest in marine aquaculture, the current study sought to monitor and investigate some of the pathogens affecting marine fish that could pose a threat to marine aquaculture and result in high mortality rates in southern Iraq. The marine Soleidae, a species of importance in marine aquaculture because of its ease of rearing, was among a variety of marine fish that were examined. Only one of the thirty fish that were inspected had an infection rate of 3.3%, which is a very low percentage. The findings demonstrated that the nematode worm Huffmanela (Nematoda: Trichosomoididae: Huffmanelinae) lays its eggs in the intestinal tissues of the fish Brachirus orientalis (Bloch & Schneider, 1801) of the Soleidae family, which are unique sites for this kind of infection. Multiple tiny black spots, which are outward indicators of infection, were present on the serous and subcutaneous layers, characterizing the infection. Huffmanela species are known for their polyploid, thick-walled, and tissue-clustering eggs, which were observed both histologically and under a microscope. Additionally, pathological examinations showed that the eggs were rough, brown-shelled, oval to spindle-shaped, and encircled by localized fibrosis and tissue tears. This study adds to our understanding of the nematode biodiversity in the northern Arabian Gulf by being the first to report Huffmanela infection of B. orientalis in Iraqi marine waters.

Trenches apart, yet worm to worm: inter- and intra-trench comparisons reveal divergent and convergent dynamics in hadal nematode biodiversity

Hydrothermal vent fields are habitats to a diverse array of benthic organisms, including several nematode species, which represent a significant portion of the biodiversity in these environments. Despite their ecological importance, most research on hydrothermal vents has focused on macro-invertebrates. As a result, vent nematode biodiversity remains largely unexplored, especially in peripheral and inactive structures, underscoring the need for further investigation. A sampling program conducted in 2017 and 2018 along a gradient of venting activity led to the collection of a number of Draconematidae species in various habitats. In this article, we introduce Dracograllus miguelitus sp. nov., the first species of the genus described at a hydrothermal vent field, sampled from a visually inactive sulphide structure. The samples were collected at the Lucky Strike vent field, on the Mid-Atlantic Ridge, using the suction sampler of the Remotely Operated Vehicle Victor6000. Specimens were retrieved from an edifice covered by a black layer of manganese oxy-hydroxides, with no local visible hydrothermal activity, at a depth of 1.639 m. Samples were sieved on a 32 µm mesh onboard, sorted and, for nematodes, identified to species level back in the lab. Fluorescent images were obtained using the ApoTome Fluorescence Microscope Module, and 3D observations were possible through the depth change method. We established D. miguelitus sp. nov. as a new species based on the combination of the following characters: four cephalic adhesive tubes (CATs), an elongated loop-shaped amphid with varying branch sizes between males and females, and a circular amphid in juveniles. Additionally, females display a minute setae emerging from the vulvar aperture. In males, the posterior adhesive tubes (PATs) are arranged in four longitudinal rows: two sublateral rows, each containing 10-12 PATs, and two subventral rows, consisting of 10 PATs in each. In females, sublateral and subventral rows with 13 PATs each. So far, D. miguelitus sp. nov. is the first species of the genus to be described from a hydrothermal environment and the deepest one. Beyond the formal description of this new species, we provide ecological and taxonomic backgrounds on Draconematidae at hydrothermal vents, with insights into the genus distribution, biogeography, and nomenclatural issues. This discovery contributes to the knowledge of Draconematidae biodiversity, and highlights the importance to investigate nematode communities at species-level, data that is often missing at vent studies. Additionally, it underscores the significance of preserving inactive hydrothermal habitats, which are threatened by deep-sea mining activities.

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.

This study was conducted to determine the nematode biodiversity in corn (Zea mays L.) growing areas in Tekirdağ, Türkiye. For this purpose, corn fields in Malkara, Şarköy, Süleymanpaşa, and Hayrabolu were surveyed, and a total of 62 soil samples were collected from a soil depth of 0-60 cm. Nematodes were isolated by centrifugal flotation using 475 g/L sugar solution. Nematode identifications were made using polytomous keys. In the study, 30 nematode genera were identified, and among these genera, 11 were plant parasites, three were fungal feeders, nine were bacterial feeders, five were omnivores, and two were predators. Some of the plant parasitic species identified in the study included Ditylenchus dipsaci, Helicotylenchus digonicus, H. varicaudatus, Pratylenchus penetrans, P. thornei, P. neglectus, Paratylenchus nainianus, Rotylenchus cypriensis, and Tylenchorhynchus annulatus. Among all Aphelenchus (Aphelenchida: Aphelenchidae), Cephalobus (Rhabditida: Cephalobidae), Filenchus (Tylenchida: Tylenchidae), and Geocenamus (Tylenchida: Merliniidae) were the most abundant and common genera and the heat map generated with XLSTAT represents the nematode abundance. To the best of our knowledge, this is the most recent taxonomic study on nematode diversity in corn fields in Tekirdağ province.

Abstract. Pradana AP, Izzatika ZN, Addy HS. 2025. Molecular detection of Dorylaimus stagnalis (Durjan, 1845), in the rhizosphere of soybean plants in Jember District, Indonesia. Biodiversitas 26: 1913-1919. Nematodes, members of the phylum Nematoda, are ubiquitous soil organisms whose community composition provides critical insights into soil health and ecosystem function. The genus Dorylaimus is of particular ecological interest due to its adaptability and role in nutrient cycling within diverse terrestrial environments. This study documents the first molecular and morphometric confirmation of Dorylaimus stagnalis (Dujardin, 1845), in the rhizosphere of soybean (Glycine max) in Jember District, Indonesia. Soil samples were systematically collected from 15 distinct sites within soybean fields using a standardized protocol, and nematodes were extracted via the Whitehead tray method. Detailed morphological observations were made using an Olympus BX50 light microscope, and morphometric measurements were obtained following De Man’s ratios, which collectively confirmed diagnostic features consistent with D. stagnalis as reported in previous studies. Molecular characterization was performed by PCR amplification of the 28S-D2D3 region followed by Sanger sequencing. Subsequent phylogenetic analysis revealed 94% sequence similarity to established reference sequences (AY592994.1 and AY592995.1) and a low genetic distance of 0.1058, thereby substantiating the taxonomic identity of the specimens. This study’s integrative approach not only verifies the presence of D. stagnalis in Indonesia but also indicates subtle morphometric variations potentially attributable to local environmental pressures. Its findings expand the current understanding of nematode biodiversity in Indonesian agroecosystems and provide a framework for future research on sustainable soil management practices.

The current study was conducted in 2024 in Süleymanpaşa, Tekirdağ to determine the nematode biodiversity in the black poplar [Populus nigra L. (Malpighiales: Salicaceae)], Himalayan cedar [Cedrus deodara (Lamb.) G.Don (Pinales: Pinaceae)], cypress [Cupressus sempervirens L. (Pinales: Cupressaceae)], oriental plane [Platanus orientalis L. (Proteales: Platanaceae)], common ash [Fraxinus excelsior L. (Lamiales: Oleaceae)], stone pine [Pinus pinea L. (Pinales: Pinaceae)], and black locust [Robinia pseudoacacia L. (Fabales: Fabaceae)] growing areas. Soil samples were collected from the 0-60 cm soil depth of each tree rhizosphere. Nematodes were extracted using the centrifuge flotation method, and identifications were made using polytomous keys. In the study, 38 genera were identified in the rhizosphere soil of stone pine, 32 in Himalayan cedar, 36 in cypress, 34 in oriental plane, 31 in black locust, 27 in common ash, and 27 in black poplar. Cephalobus Bastian, 1865 (Rhabditida: Cephalobidae), Aphelenchus Bastian, 1865 (Aphelenchida: Aphelenchidae), Filenchus Andrassy, 1954 (Tylenchida: Tylenchidae), and Geocenamus Thorne & Malek, 1968 (Tylenchida: Merliniidae) were common genera across all tree species. Taxonomic diversity indices were calculated to compare nematode diversities at different taxonomic levels. The Shannon diversity index (H′) ranged from 2.99 to 3.41, Evenness (J′) from 0.90 to 0.95, Maturity index (MI) from 2.29 to 2.48, and Plant-parasitic index (PPI) from 2.84 to 3.02. Analysis by trophic groups revealed that plant parasitic and bacterial feeder nematodes were more prevalent in all tree species.

During an investigation on the biodiversity of plant-parasitic nematodes in the Khuzestan province, southwestern Iran, two populations of Mesocriconema curvatum were discovered around the rhizosphere of pomegranate and Bermuda grass. The study included the morphological and morphometric characters of the recovered populations and compared them to those of other populations reported from different locations. The phylogenetic relationships of the Iranian populations of M. curvatum with representatives of the family Criconematidae were reconstructed using the partial sequences of the small subunit, D2-D3 expansion segments of the large subunit, and internal transcribed spacer regions of ribosomal DNA based on Bayesian inference. In three inferred SSU, LSU, and ITS phylogenies, the Iranian populations of M. curvatum formed a clade with other sequences of the species with high support. M. rusticum and M. antipolitanum have sister relationships with M. curvatum in the SSU and LSU phylogeny, respectively. To our nowledge, this is the first morphological and molecular characterization of M. curvatum in Iran Key Words: ITS rDNA, LSU rDNA, Mesocriconema, phylogeny, SSU rDNA

During a survey of the nematode biodiversity in the Petrel wetland (central Chile), a population of Heterorhabditis sp. was found in the coastal dune samples. Morphological, morphometric, and molecular studies indicated that this nematode belonged to the megidis group, and represented a novel species, which we named Heterorhabditis caligo n. sp. This nematode species resembles H. marelatus but it is different in the morphometrics of its infective juvenile in the following ways: pharynx length (135–150 μm vs. 120–138 μm), and the position of the excretory pore from the anterior end (105–128 μm vs. 81–113 μm). In males, the fourth and eighth pairs of the bursal papillae are shorter and do not reach the edge of the bursa in H. caligo n. sp., whereas all the papillae in H. marelatus reach the edge of the bursa. The excretory pore of amphimictic females of H. caligo n. sp. is located more posteriorly than in those of H. marelatus 193 (169–224) μm vs. 157 (139–178) μm, respectively. Phylogenetic analyses of the genus based on whole nuclear and mitochondrial genome sequences and on five gene markers showed a clear separation of Heterorhabditis caligo n. sp. from the other species, placing it within the megidis group.

The present study describes a new Ditylenchoides species, isolated from Meknès, Morocco, during nematode surveys conducted to investigate the biodiversity of plant-parasitic nematodes in Mediterranean olive groves and adjacent patches of natural vegetation. Application of integrative taxonomical approaches clearly verified that it is a new species designated herein as Ditylenchoides morocciensis sp. nov., also representing the first report of the genus in Morocco. The new species is parthenogenetic, characterised by a short body 460 (373-528 μm); stylet delicate, relatively short, 8.7 (8.0-9.0) μm long with rounded basal knobs; six lines in the lateral fields; median bulb of pharynx oval, muscular and valvate; secretory-excretory pore located at the level of basal pharyngeal bulb region; vulva located at 79.9 (76.9-81.3) % of body length; relatively long post-vulval uterine sac 29.1 (20.0-39.0) μm; and a subcylindrical tail 24.4 (22.0-28.0) μm long, with a bluntly rounded tip. The results of molecular analysis of D2-D3 28S rRNA, ITS rRNA, partial 18S rRNA, and cytochrome oxidase c subunit 1 (COI) gene sequences support for the new species status and clearly separated D. morocciensis sp. nov. from all other species within Ditylenchoides. Phylogenetic analyses of ribosomal markers (D2-D3 28S rRNA and partial 18S rRNA) of this study confirms that Ditylenchoides is a monophyletic genus, clearly separated from other genera within Anguinoidea.

During nematode surveys conducted to investigate the biodiversity of plant-parasitic nematodes in Mediterranean olive groves with different management strategies (organic and conventional), a nematode population of the genus Neothada was detected in southern Spain. Application of integrative taxonomical approaches clearly demonstrated that it is a new species described herein as Neothada olearum sp. nov., also representing the first report of the genus in Spain. The new species is amphimictic, characterised by a short body (563-774 μm); cuticle widely annulated (2.5-3.0 μm); total number of body annuli 214-226; 16 longitudinal ridges giving a tessellate body surface; stylet without distinct basal knobs (9.0-11.0 μm); and tail elongate-conoid, with tip bluntly rounded. The results of molecular analysis of D2-D3 28S rRNA, ITS rRNA, partial 18S rRNA, and cytochrome oxidase c subunit 1 (COI) gene sequences support for the new species status and clearly separated from N. major and other species within Neothada. Phylogenetic analyses of ribosomal and mitochondrial markers of this study suggested that Neothada is a monophyletic genus, clearly separated from Thada.

Microplastics (MPs), defined as plastic particles of less than 5 mm, pose a significant global environmental threat, particularly in aquatic ecosystems, due to their persistence and potential harmful effects on wildlife and human health. They can absorb persistent organic pollutants (POPs), like polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs), raising concerns about their impact on biota. To elucidate this impact, the present study employed attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) to analyse the characteristics of MPs sourced from commercial cosmetics. We investigated the toxicity of MPs on Caenorhabditis elegans and two entomopathogenic nematode species, Steinernema feltiae (the enviroCORE strain SB12(1)) and Steinernema carpocapsae (a commercial strain from e-NEMA) in laboratory bioassays. Nematodes were exposed to various concentrations of MPs and other pollutants, including atrazine, 1,3-dichloropropene, naphthalene, and fluorene, in controlled settings over 72 to 96 h. Additionally, high-throughput 18S rDNA sequencing was used to analyse nematode biodiversity in sediments from the River Barrow (RB) in SE Ireland. Our findings revealed that MPs increased nematode mortality and adversely affected community structure, as indicated by nematode maturity and sigma maturity indices, suggesting a potential disruption of the ecological balance in river sediments. This highlighted the ecological risks posed by MP pollution and emphasised the urgent need for further research into the health of benthic ecosystems in Ireland, particularly in relation to how MPs may influence nematode community dynamics and biodiversity.

Plant parasitic nematodes (PPNs) are one of the major threats to various crops including cereals. In wheat and barleyproduction, the profitability of cultivation heavily depends on the management of cyst nematodes (CNs), especially on Heteroderaavenae, H. filipjevi, and H. latipons. In this study, field surveys were conducted in wheat and barley cultivation systems of Uşak Provinceto reveal the presence and diversity of PPNs. In total, 80 wheat and barley fields were surveyed, and samples (soil and root) wereprocessed for the isolation and identification of PPNs. The PPN genera were identified to the species level based on morphologicaland morphometric characters. CNs were further analyzed using molecular methods. In total, 17 species belonging to 10 genera wereidentified. Helicotylenchus Steiner, Pratylenchoides Winslow, Merlinius Siddiqi, and Heterodera Schmidt were the most prevalent andabundant genera. The Shannon diversity index averaged at 2.51 in the wheat and barley fields, indicating a moderate level of biodiversity.The evenness value of 0.798 suggests a high degree of uniformity among migratory PPNs. The results indicate that PPNs have a seriousimpact on reducing grain yield and quality in the wheat- and barley-growing areas of Uşak Province.

Soil health in Moroccan olive agroecosystems: The bioindication role of terrestrial nematode dynamics

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.

Summary During a survey on the biodiversity of nematodes in the Petrel lagoon (central Chile), a population of Leptolaimus was found in sediment samples. Morphological, morphometric and molecular data indicated that the recovered nematode is a new species. This nematode belongs to the group in which the males only have four pre-cloacal tubular supplements present, and females have no supplements. The new species can be separated from the other species of the group by the length of both males and females (843-1060 μm), the tail length (118-208 μm), the shape of the gubernaculum, and the arrangement of the caudal setae in males (a pair of ventral precloacal setae at level of spicules, a pair of dorsal post-cloacal setae, two subventral and two subdorsal caudal pairs. The differences from closely related species L. gerlachi, L. praeclarus, L. octavus, L. hydrothermalis, L. vipriensis, and L. hadalis are discussed. The recovered population is described herein as Leptolaimus petrelense n. sp.

Parasitic nematodes of the oxyurid family Pharyngodonidae are commonly found across reptile orders, with species of the genus Spauligodon Skrjabin, Schikhobalova & Lagodovskaja, 1960, being among the most common ones. However, scant information exists regarding the prevalence of Spauligodon nematodes in Italian reptile populations. Although two Spauligodon species have been reported from southern Italy, the presence of these worms in the rest of the country remains unknown. In this research, we describe Spauligodon orobicus sp. nov. from an Italian common wall lizard Podarcis muralis (Laurenti, 1768) of northern Italy. The new species is distinct from other known species both at the morphological and molecular level. The study increases the knowledge on the biodiversity of Spauligodon nematodes and in general on the biodiversity of Italy, and adds northern Italy to the geographical range of this nematode genus.http://zoobank.org/urn:lsid:zoobank.org:act:29DB5E90-9CB5-46A3-8471-FEE0395FA29A

Soil nematodes are among the most significant soil-dwelling organisms in forest ecosystems. However, the factors that shape the distribution of soil nematodes are still not well explored. Therefore, we collected soil samples from 20 forest sites along the eastern transect of China and sequenced 18S rRNA V9 region to reveal the biodiversity of soil nematodes. Our study found that soil nematode richness is higher in temperate mixed needleleaf and broadleaf forests compared with the other four vegetation regions. Soil physiochemical properties overrode climatic factors to be the primary drivers of soil nematode richness and community composition. Importantly, the soil nematode richness significantly enhanced ecosystem multifunctionality, especially bacterial biomass and enzyme activities, with a determination coefficient (r2) of 0.23, suggesting that soil nematodes played essential roles in the forest ecosystem.