A new species of fauveliopsid annelid polychaete, Laubieriopsis sankalpae sp. nov., is described based on specimens collected from the summit of a seamount in the southeastern Arabian Sea. Laubieriopsis sankalpae inhabits deep-water sediments and can be distinguished from the other congeners by having 18 chaetigers, chaetigers 1–3 bearing four bidentate acicular chaetae per rami, its fourth segment transitional with one knife-like acicular and long hirsute capillary chaetae per rami, and a genital papilla unpaired, on left side near the posterior margin of chaetiger 8. This new species also represents the first record of the genus in the Indian Ocean.

A new entomopathogenic nematode, Steinernema chainatense n. sp., was isolated during sampling in a cassava field in Chai Nat Province, Central Thailand. A combination of morphological, morphometric, and molecular traits places the new species within the longicaudum clade of the glaseri-group. Infective juveniles (IJs) of S. chainatense n. sp. are characterised by a body length of 871 (798–939) μm, a maximum body diameter of 27 (24–30) μm, and a lateral field with eight equally developed ridges at mid-body and a formula of 2, 6, 8, 2. First-generation males are characterised by large, brown spicules, 88 (80–95) μm long, with a well-developed velum. The male genital papillae number 25 in total, comprising 12 pairs and a single midventral papilla. The internal transcribed spacer (ITS) and D2–D3 sequences differ from those of other members of the longicaudum clade by 3.6–10.4% and 1.5–3.5%, respectively. Phylogenetic analysis based on the ITS region of rDNA indicates a close relationship between S. chainatense n. sp. and S. taiwanensis, S. adamsi, S. guangdongense, and S. longicaudum, with S. taiwanensis as its sister taxon. The bacterial symbiont of S. chainatense n. sp. is the recently described Xenorhabdus thailandensis. These morphological and molecular differences support the recognition of S. chainatense n. sp. as a distinct species.

During an oceanographic campaign led by the Museum National d’Histoire Naturelle and the Institut de Recherche pour le Développement to explore the biodiversity of Walters Shoal Seamount in the Indian Ocean, a new species of Morgana was discovered. Until now, this genus was monotypic with the only known species described from shallow waters off São Paulo, south-eastern Brazil: M. bisetosa Nogueira & Amaral, 2001. This new deep-sea species, M. waltershoalensis sp. nov., is characterised by the absence of branchiae, the notopodia beginning from segment 4 and the neuropodia from the 6th, a great number of segments with notopodia (n = 53), and the presence of a pair of large nephridial papillae dorsally, on segment 3. This species differs from M. bisetosa by the absence of eyespots, the shape of both noto- and neurochaetae and by the presence of a large pair nephridial papillae on the third segment. Following this study, the boundaries of the genus have been modified, particularly with regard to the number of segments with notopodia, the presence of eyespots and the large papilla on segment 3.

Updated taxonomic data are presented for 34 species belonging to 12 vetigastropod families collected from Canopus Bank, a seamount off northeastern Brazil. Distributional ranges are extended for 12 species, and bathymetric limits are revised for another 12. Five species: Emarginula suspira, Hemimarginula hemitoma, Profundisepta volcano comb. nov., Homalopoma boffii, and Parviturbo brasiliensis are reported for the first time from northeastern Brazil, extending their known distributions northward from southeastern waters. Five additional species: Arene flexispina, Diodora fluviana, Diodora listeri, Haplocochlias risoneideneryae, and Solariella quinni exhibit notable range expansions in Brazilian waters. The Caribbean species Dentistyla dentifera is documented for the first time in the southwestern Atlantic. Four new generic combinations are proposed in light of new evidence: P. volcano comb. nov., Puncturella canopa comb. nov., Puncturella cearensis comb. nov., and Puncturella columbaris comb. nov. Three new species are described based on shell morphology: Arene asteria sp. nov., distinguished by its low, keeled shell with a star-like outline and a strongly sculptured base and operculum; Parviturbo cancellifer sp. nov., characterised by its broad, tricarinate shell with a lattice-like sculpture; and Parviturbo durian sp. nov., noted for its strongly nodulose, spiny shell with a wide circular aperture bearing nine denticles and a distinctively sculptured base. Comparisons with related taxa are supported by high-resolution photography, scanning electron microscopy, and computed tomography reconstructions.

A new nematode population of the genus Ficophagus was recovered from figs of Ficus amplissima from ICAR-Indian Agricultural Research Institute, New Delhi, India. It is described herein as Ficophagus siddiqii n. sp., distinguished among all known species of the genus by its slender, cylindrical female body and presence of four faint lateral incisures at mid-body, with the outermost pair being the most prominent; a short post-uterine sac (PUS; 5.0–10 μm), a secretory-excretory pore situated near the lips, amoeboid sperm, and three pairs of subventral papillae on the male tail. Conoid tail in both sexes; the male tail tip broadly rounded without mucro and female tail tip pointed or spike-like projection. Gubernaculum absent, rose-thorn-shaped spicules with relatively high condylus – rounded to truncate. This species is also distinguished by its biogeography and host plant, as it is collected from Ficus amplissima. Further, it is characterised by molecular sequences of 18S SSU, 28S D2–D3, Cytochrome c Oxidase Subunit I (COI), and Internal Transcribed Spacer (ITS). Molecular comparisons of the Indian population of Ficophagus siddiqii n. sp. with other Ficophagus species using D2–D3, SSU, COI, and ITS sequences revealed a clear separation of Ficophagus siddiqii n. sp. from other Ficophagus species.

A new needle nematode, Longidorus parasabalanicus sp. nov. (Nematoda: Longidoridae), was collected from the rhizosphere of Astragalus spp. in mountainous areas of northern Iran. The species is characterised by a medium-sized body (female 4.0–4.8 mm; male 4.3–5.1 mm), lip region anteriorly flattened and laterally rounded, ca 12.5–14.5 μm wide, and separated from the body by a shallow depression, amphidial fovea pocket-shaped without basal lobes, moderate odontostyle (75.0–84.0 μm) and odontophore (50.0–58.0 μm), and guiding ring located at 27–33 μm from the anterior end. The pharyngeal bulb has the common arrangement of pharyngeal glands. Females have a vulva almost equatorial (V = 50–56%), short tail rounded to bluntly conoid, 41.0–47.0 μm long (c = 89.0–113.0, c′ = 0.9–1.2), with two pairs of caudal pores and a broadly rounded terminus with distinct radial lines in the hyaline region. Males are common, with spicules 68.0–80.0 μm long and eight to ten ventromedian supplements. All four juvenile stages are present, with the first-stage juvenile having a conoid tail, dorsoventrally curved with a rounded terminus. The polytomous codes for the new species are: A23-B2-C3(2)-D3-E1-F2-G1(2)-H12-I2-J1-K6. Morphologically, L. parasabalanicus sp. nov. is most similar to L. sabalanicus, and together with L. tabrizicus and L. paratabrizicus, belongs to a closely related species complex, from which it can be distinguished by a combination of subtle but consistent morphometric characters. Molecular phylogenetic analyses based on D2–D3 expansion segments of 28S rDNA, partial 18S rDNA, ITS1, and mitochondrial COI sequences support its recognition as a distinct lineage within the genus. Phylogenetic trees recover the new species in a well-supported clade with L. sabalanicus and other closely related species from Iran and the Mediterranean. This study provides comprehensive morphological, morphometric, and molecular data for delimiting the new species and contributes to understanding Longidorus diversity in Iran and adjacent regions.

A new entomopathogenic nematode, Steinernema hattingi n. sp., was isolated during a survey in Mpumalanga Province of South Africa. Morphological and morphometric traits place the species in the glaseri-group, characterised by large infective juveniles (IJs) with average body length exceeding 1000 μm. The IJs of S. hattingi n. sp. have a mean body length of 1059 μm, lateral fields composed of eight equally spaced ridges (nine incisures) at mid-body (formula 2, 6, 8, 4, 2), a relatively short tail (c ratio 16 on average) with a hyaline region occupying approximately 45% of its length, and are relatively slender (a ratio 33 on average). Male spicules are curved, brown, with a pointed tip and an elongate manubrium (length/width ratio 1.8:1); male tails are non-mucronate or occasionally with a short papilla-like mucron in second-generation males. First-generation females have a moderately protruding, slightly asymmetrical vulva without postanal swelling, whereas second-generation females display a protruding, asymmetrical vulva and a slightly developed postanal swelling. The species is further characterised by sequences of the internal transcribed spacer (ITS) and partial 28S rDNA (D2–D3) regions. Phylogenetic analyses place S. hattingi n. sp. within the Khoisanae clade of the glaseri-group.

Species of Hexangium (Microscaphidiidae) were collected from 12 species of rabbitfishes (Siganidae) from multiple Indo-West Pacific locations: three on the Great Barrier Reef in Queensland, two in south-east Queensland, Ningaloo Reef in Western Australia, New Caledonia and Japan; no specimens were found from Palau or French Polynesia. Parallel molecular (cox1 mtDNA, ITS2 and 28S rDNA) and morphological analyses, together with consideration of host and geographical distribution, lead us to recognise six species. Specimens from Siganus fuscescens (Houttuyn) from Japan are identified as the type species, H. sigani Goto & Ozaki, 1929, which was originally described from S. fuscescens from off Japan. Hexangium affinum Tubangui & Masiluñgan, 1944, originally described from Siganus javus (Linnaeus) from the Philippines but previously considered a synonym of H. sigani, is reinstated, and H. secundum Annereaux, 1947 is considered its junior synonym. Four new species are described: H. urabeae n. sp., H. kuramochii n. sp., H. robustum n. sp. and H. reimeri n. sp. Based on morphology alone, individual specimens of several combinations of these species are difficult to distinguish. Although none of the combinations of species are entirely mutually cryptic, we consider taxonomy of this genus to be dependent on molecular analysis; morphological distinction of species requires substantial numbers of well-preserved specimens. Most species of Siganus examined harbour two or three species of Hexangium; sometimes one species is dominant, but in several two species were both common. All six Hexangium species recognised here have been found in multiple locations; four species were found at each of two Great Barrier Reef sites.

Neodiplostomum Railliet, 1919, is a cosmopolitan genus that parasitises mainly the intestines of birds of prey, and occasionally those of passerines, cuculiforms, and mammals. Adults of three undescribed species of Neodiplostomum were obtained from five bird species from three families (Accipitridae, Cuculidae, and Tyrannidae) in a single locality. Four molecular markers, namely, the small (SSU) and large (LSU) subunits and internal transcribed spacers (ITS1 and ITS2 plus 5.8S) from nuclear ribosomal DNA, and cytochrome c oxidase subunit 1 (cox 1) from mitochondrial DNA, were sequenced from specimens of the three species. The newly obtained sequences were aligned with other sequences of Neodiplostomum spp. downloaded from GenBank. Maximum likelihood and Bayesian analyses based on each molecular marker revealed that the specimens of the three undescribed species of Neodiplostomum formed three independent lineages with high values of genetic divergence; thus, they are recognised herein as three new species: Neodiplostomum acatlotlii n. sp., N. papaloapanensis n. sp., and N. leoni n. sp. The new species showed morphometric differences in the body size, prosoma, opisthosoma, suckers, holdfast organ, testes, ovaries, and eggs. Our study also revealed that the three new species are distributed sympatrically in the Veracruzan biogeographical province in the Neotropical region of Mexico and use different ways of transmission to complete their life cycles.

A single specimen of Chlopsis slusserorum Tighe & McCosker, 2003 is documented for the first time from the Indian Ocean, based on the specimen (250 mm total length) collected from the Bay of Bengal. Previously, the species was known only from its type localities, Fiji and the Solomon Islands. Additionally, this study presents the first molecular data for C. slusserorum, based on the mitochondrial cytochrome c oxidase subunit 1 gene. Detailed taxonomic information, along with molecular and phylogenetic analyses, is provided in the present study.

Phenotypic plasticity allows parasites to modify their morphology in response to the ecological and physiological conditions induced by their hosts. In digeneans with complex life cycles and multiple definitive hosts, host-induced variation may complicate species delimitation and taxonomic diagnoses. In this study, we characterised intraspecific morphological variation in Mesorchis uruguayensis (Digenea: Echinochasmidae), a trematode that parasitises fish-eating birds, using an integrative morphological approach. Thirty-eight adult specimens previously collected from five definitive host species in Mexico and molecularly identified as M. uruguayensis were examined. Scanning electron microscopy (SEM) was used to assess qualitative diagnostic traits, and principal component analysis (PCA) based on 19 linear measurements was used to explore morphometric variation among host-associated groups. All specimens retained the characteristic head collar with 22 spines, 10 small spines along the anterior margin of the oral sucker, and a consistent general pattern of tegumental spines. The first two principal components explained 80.9% of the total morphometric variation. However, the host-associated group overlapped substantially, with some differences. Body size, the dimensions of reproductive organs, and the ventral sucker contributed most strongly to this variation. Because all specimens were molecularly conspecific, these differences represent intraspecific morphological variation rather than species-level divergence. Host identity constitutes a biologically plausible source of this variation through differences in intestinal physiology, resource availability, and other host-associated conditions; however, geographic origin, parasite maturity, infection intensity, and individual host condition may also contribute. Our findings emphasise the value of combining stable qualitative characters, morphometric analyses, and molecular evidence to interpret morphological variability and avoid taxonomic misidentification in digeneans.

Freshwater streams in Iraq harbour a remarkable diversity of fish species. A similarly high diversity has also been recorded for diplozoid parasites, which are commonly associated with the cyprinoid fishes. A new species, Paradiplozoon vorax sp. nov., is described from Leuciscus vorax from Al-Gharraf River. This is the 21st Paradiplozoon species recorded from Iraq and presumably the 11th species from this fish host. Phylogenetic analyses based on the ITS2 rDNA region revealed a close relationship between P. vorax sp. nov. and P. pavlovskii, which exhibits a wide geographical range spanning Europe and the Middle East. Although these two species are morphologically similar, they differ in important characters such as the number of folds in the hindbody, the shape of postovarian caecum or the shape of anterior joining sclerite of clamps. It is hypothesized that these two species originated by vicariant speciation from a common ancestor associated with ancestral Aspius-like leuciscids.

Syphatineria (Africanoxys) cepapi Hugot, 1981, a pinworm in the family Oxyuridae, has been described from Smith’s bush squirrel, Paraxerus cepapi Smith, 1836, in South Africa. The current taxonomic description is based on a few specimens from a single squirrel individual and a single locality. To substantiate the species description, additional morphological data derived from 70 male and 70 female St. cepapi specimens were obtained from 79 P. cepapi host individuals, and these originated from 7 South African localities. Ten St. cepapi individuals were also sequenced for the mtDNA Cytochrome Oxidase I gene to provide molecular barcode information for the species and an additional phylogenetic context; 2 individuals were also sequenced for the 18S rRNA gene fragment. In total, 11 112 St. cepapi individuals were recorded and the prevalence per locality ranged between 50 and 100%. Female nematodes (62%) were more common than males (38%). All defining morphological features were measured and provided more insights into the original description of St. cepapi and other Syphatineria Chabaud and Biocca, 1955 species that are associated with African squirrels. Several key features in males – 2 mamelons, a simple spicule and an elongated gubernaculum with an accessory hook with 2 laterally situated horns, were present. Females were characterized by a long, slender shape, a protruding vulva and eggs with a flattened side and small operculum. Phylogenetic analyses placed St. cepapi monophyletic and well separated from other potentially closely related species. The additional morphological and molecular data strengthen the species diagnosis and support its taxonomic distinctness.

Anoplocephalidae (Cestoda: Cyclophyllidea) is a diverse family, with the subfamily Anoplocephalinae comprising 59 genera that primarily parasitize the digestive tract of rodents and birds. Monoecocestus threlkeldi was originally described from the northern vizcacha, Lagidium peruanum, in Junin, Peru, and subsequently reported in cricetids (Holochilus spp.) in Argentina and Bolivia. In the present study, we describe a new species of the genus Monoecocestus parasitizing the southern vizcacha, Lagidium viscacia, based on specimens collected in Puno, Peru, at an elevation of 3932 m a. s. l. A total of 45 specimens of the new species were obtained and processed for morphological and molecular analysis. For molecular analysis, DNA sequences of three markers were generated: the nuclear 18S, 28S, ITS, and mitochondrial cox1. The molecular data were compared with sequences available in GenBank, confirming its inclusion in the genus Monoecocestus. Morphologically, the new species is similar to M. threlkeldi, but it can be distinguished by its smaller body size, scolex, cirrus pouch, and number of proglottides. The description of the new species Monoecocestus viscaciae improves our understanding of the diversity of cestodes in high-altitude Andean ecosystems and provides new insights into host specificity within the genus Lagidium.

A new species of Calicotyle (Monogenea: Monocotylidae) is described from three deepwater catshark species (Elasmobranchii: Pentanchidae) collected off Iceland. Calicotyle carmenae n. sp. is diagnosed as a species of Calicotyle possessing a haptor with one central and seven peripheral loculi, two hamuli, and several hooklets. It is distinguished from all congeners by the absence of eye spots, having a once-looped male copulatory organ, two U-shaped vaginae, and intercaecal vaginal pores. A molecular phylogenetic analysis based on 28S ribosomal DNA sequences placed Calicotyle carmenae n. sp. within a clade of other Calicotyle species infecting selachians and holocephalans, while revealing clear genetic divergence from these congeners (8.2–11.1%; 74–99 bp). In addition, the morphology and host specificity of C. carmenae and its congeners are discussed. Some inconsistencies and insufficiently described anatomical features in other species of the subfamily Calicotylinae are highlighted, which evidence a need for a revision of this taxon. The study also provides the first record of a species of Calicotyle from pentanchid sharks, highlighting the potential for further discoveries as research expands into different hosts and deeper, underexplored marine ecosystems.

Despite several recent studies, the helminth diversity of small mammals in South Africa remains poorly understood. During a survey conducted from 2023 to 2025 on the helminth assemblages of rodents in the Western Cape Province, South Africa, nematodes were collected from the stomach of a female Micaelamys namaquensis in the Nama-Karoo biome. For one of the nematode species identified, morphological characters, based on light and electron microscopy, corresponded to the genus Gastronodus: a short, heavily sclerotized buccal capsule armed with 6 teeth, the presence of 3 pairs of pedunculate postcloacal papillae as well as dissimilar and unequal spicules in males and a vulva situated at the level of the glandular oesophagus in females. The presence of 3, rather than 2, pairs of postcloacal pedunculate papillae distinguishes our specimens from the closely related genera Cylicospirura, Skrjabinocercina and Spirocerca. Furthermore, the presence of 4–5 vs 6–7 pairs of pedunculate precloacal papillae distinguishes them from their single currently recognized congener, Gastronodus strasseni sampled from Suncus murinus in India. Based on these results, we here describe Gastronodus karooensis n. sp. Phylogenetic analyses of the mtDNA cox1 gene suggest some affiliation with the genus Spirocerca and provide some support for their placement in the Spirocercidae. This is the first record of the genus Gastronodus in Africa. The description of a new species of Spirocercidae from M. namaquenis highlights the need for further studies as the nematode diversity in wild hosts in South Africa is currently underestimated.

Population genetic analysis of mitochondrial DNA barcodes, comprised of a standard segment of the cytochrome c oxidase subunit I gene (COI or cox1), was conducted on Spoladea recurvalis (Fabricius), an important agricultural pest commonly referred to as the Hawaiian beet webworm. Results of genetic diversity analyses indicate significant population structure between samples mainly from Australia and nearby regions and those from North America, Africa, Europe, and Asia. Adults of the two groups are morphologically indistinguishable but are characterised by diagnostic barcode nucleotides and genetic diversity values. Factors possibly involved in driving genetic divergence in S. recurvalis in the Australian region are briefly discussed.

Ferrisia dasylirii (Cockerell) (Hemiptera: Coccomorpha: Pseudococcidae) is a polyphagous mealybug species and native to North America, but has spread to Asia and Africa. In this study, we report F. dasylirii for the first time from China using an integrated taxonomy approach combining morphological characters and molecular analyses of the mitochondrial cytochrome oxidase subunit 1 gene. It was found on 12 tropical fruit species in Hainan Province: Annonaceae: Annona squamosa L. and A. squamosa ‘Purple’; Myrtaceae: Eugenia brasiliensis Lam. and Psidium guajava L.; Malvaceae: Theobroma cacao Linn.; Lecythidaceae: Lecythis pisonis Cambess.; Sapotaceae: Pouteria campechiana (Kunth) Baehni and P. sapota (Jacq.) H.E.Moore & Stearn; Rubiaceae: Coffea liberica W. Bull ex Hiern; Cunoniaceae: Davidsonia pruriens F. Muell; Arecaceae: Areca catechu Linn.; Musaceae: Musa nana Lour.; Malpighiaceae: Malpighia emarginata Sesse & Noc.ex DC.; and Phyllanthaceae: Phyllanthus emblica Linn. This record increases the known geographic range of F. dasylirii and underscores the importance of combined morphological and molecular approaches for accurate mealybug identification.