Two Xiphinema species, one new and one known, were found from Bushehr province, southern Iran, and are herein described based on morphological and molecular data. These include Xiphinema pedrami sp. nov. and X. basiri, both belonging to the ‘Xiphinema non-americanum group’. The new dagger nematode is characterised by a body length of 3.54–5.00 mm, a lip region separated from the rest of body by a depression, odontostyle 128–148 μm long, 60–89 μm long odontophore, guiding ring at 107–138 μm from anterior end, female tail rounded to dorsally more convex with small bulge and four juvenile stages. Males have one pair of cloacal and three to five ventromedian single supplements. The new species belongs to morphospecies Xiphinema non-americanum group 5, characterised by having two equally developed female genital branches with uterine differentiation in the form of pseudo-Z-organ along with the rhomboid-shaped crystalloid bodies, and a short, rounded tail ending in a peg. The polytomous identification codes of the new species are A4, B2, C5a5b, D6, E56, F4(5), G23, H2, I34, J5a5b, K3, L2. Morphologically, the new species comes close to several known species (namely, X. andalusiense, X. artemisiae, X. baetica, X. hyrcaniense, X. ingens, X. macroacanthum and X. pseudocoxi) belonging to morphospecies group 5. The morphological differences of the new species and the aforementioned species are discussed. The second recovered species, Xiphinema basiri, belongs to the same group and has a pseudo-Z-organ in the shape of globular bodies close to pars dilatata uterus and short, conical, distinctly digitate tail. Integrative diagnosis was completed using molecular data obtained from partial sequences of the D2-D3 region of 28S rDNA, ITS1 rDNA, 18S rDNA, and COI mtDNA genes.

Accurate species identification is essential for biodiversity research, especially in the field of parasitological systematics. In particular, the incorporation of DNA-based methods in the study of Digenea has transformed taxonomy by allowing for precise species delimitation, clarification of life cycles, and the identification of cryptic diversity. However, to prevent taxonomic misidentification, a growing concern in public sequence databases, these molecular techniques must be supplemented with high-quality morphological data. This study provides an integrative assessment (combining both morphological and molecular data) of Cotylurus brandivitellatus, based on adult specimens obtained from naturally infected mute swan (Cygnus olor) in Gdańsk Pomerania. The observed morphological characteristics are consistent with the original description of C. brandivitellatus and align with the established description of the genus Cotylurus. Phylogenetic analysis, utilizing concatenated LSU rDNA and COI mtDNA markers, confirms the distinct taxonomic status of C. brandivitellatus. It forms a sister clade with C. strigeoides, which is clearly separate from other species within the Cotylurus genus. These findings validate the existence of C. brandivitellatus and offer new insights into species delineation and evolutionary relationships within Cotylurus, highlighting the importance of integrative approaches in trematode systematics.

Laetisaria macrospora is a new species of lichenicolous Corticiaceae forming light pink to coral coloured basidiomata on Physcia adscendens and P. stellaris. The basidiomata are usually located on the lower surface of the host thallus and produce basidia with four sterigmata and relatively large basidiospores, 23–34 × 11–18 μm. Phylogenetic analyses using nuITS sequences fully support the placement of the new species in Laetisaria, a genus that is recovered as monophyletic. Laetisaria macrospora was discovered in the Massif Central (France) in lichen communities growing on branches of Juniperus and Genista at the summit of the Puy de Manson.

A new species of the genus Verdeia is described from the continental slope of the Potiguar Basin, Rio Grande do Norte, Brazil at a depth of 150 m. Verdeia setosa sp. nov. is readily distinguished from its congeners by the ornamentation of the larger gnathopod 2 in males and the densely setose basis of pereopods 6–7. This is also a new record of the genus from Brazilian waters. We presented an amended diagnosis of the genus to accommodate all Verdeia species and discuss these changes. Furthermore, an identification key to the family Melitidae from Brazil is provided.

Kalicephalus (Molin, 1861) comprises 33 species of gastrointestinal snake and lizard parasites with a cosmopolitan distribution, with seven taxa occurring in the Neotropical realm. In the present study, we describe Kalicephalus atroxi n. sp., found parasitising the snake Bothrops atrox, from the Eastern Amazon in the State of Amapá, North of Brazil. We used an integrative approach that included light microscopy, scanning electron microscopy, and sequencing of the internal transcribed spacer 1 (ITS1) region to describe Kalicephalus atroxi n. sp. The new species has a buccal capsule characteristic of the genus, a slight cuticular inflation in the cephalic region. The females have an amphidelphic reproductive system, a vulva with prominent lips, and a long tail, tapering posteriorly. The males have long and alate spicules, and the copulatory bursa is lobed with dorsal rays with distinct morphology compared to their congeners. Molecular analyses and phylogenetic reconstructions cluster the new species into a well-supported clade with K. costatus costatus, from Chironius fuscus, from the same locality in northern Brazil. Kalicephalus atroxi n. sp. is the eighth species of the genus in the Neotropics, the seventh in Brazil, the second described parasitising B. atrox in Brazil, and the first species of snake nematode described in the State of Amapá.

Trematodes of the genus Paralecithodendrium parasitize bats worldwide. Among them, the identification of Paralecithodendrium longiforme and Paralecithodendrium cryptolecithum is complicated by their high morphological similarity. We studied Paralecithodendrium trematodes from the small intestine of bats inhabiting the Middle Volga region (European Russia). The aim of our study was to analyze these two Paralecithodendrium species using both morphological and molecular phylogenetic approaches. Here, we present the first complete morphological description and molecular phylogenetic analysis of Paralecithodendrium cryptolecithum from bats in Russia and confirm the validity of this species.

In the present study, species of the genus Talorchestia (Dana, 1852), found in India are discussed. Previously, six species of the genus were recorded from India including Talorchestia affinis (Maccagno, 1936); Talorchestia buensis (Bhoi, Patro & Myers, 2023); Talorchestia gracilis (Dana, 1852); Talorchestia lakshadweepensis (Trivedi, Lowry & Myers, 2020b); Talorchestia martensii (Weber, 1892); and Talorchestia spinipalma (Dana, 1852). The taxonomy and distribution of these six species are discussed. Additionally, a new species, Talorchestia dandi sp. nov., is described on the basis of specimens collected from Gujarat State, India. This new species can be differentiated from its closely related species, Talorchestia morinoi (Othman & Azman, 2007), by the comparatively longer antenna 2, the telson with higher length to width ratio, the epimeron 3 with marginal setae, and the subequal carpus and propodus of pereopod 3.

A poorly understood and partially described planktonic copepod, Labidocera gangetica Sewell, 1934, is fully described herein from the Hooghly River, a century after its initial collection from the Rangoon (now Yangon) River estuary by Sewell (1912). The complete description of L. gangetica suggests possible uncertainty regarding the validity of the species Labidocera jaafari Othman, 1986, due to the morphological similarity in their overall body plan. In particular, the features of the leg 5 of both sexes are identical, suggesting that L. jaafari is probably a synonym of L. gangetica. Additionally, the taxonomic features of the mouthparts and swimming legs are illustrated for the first time.

This study marks the first update on Malaysia’s marine tardigrades after more than 50 years, presenting both the discovery of a new species, Batillipes malaysianus sp. nov., and a new record, Batillipes rotundiculus. The specimens were collected from the intertidal zone at Pantai Pancur Hitam, Labuan, Malaysia, during two separate sampling efforts. Despite extensive sampling, the density of marine tardigrades in the area was found to be exceptionally low, with only a single specimen of B. malaysianus sp. nov. and a limited number of other Batillipes individuals collected. The new species, B. malaysianus sp. nov., is distinguished by unique morphological features, including setae scattered across the ventral cuticle – a trait not observed in any other species of the genus – and constricted primary clavae, a characteristic absent in other species of the B1 toe arrangement group. Additionally, B. rotundiculus represents the first confirmed record of this species in Malaysia, expanding its known distribution. This study also updates the global species count of Batillipes to 42, incorporating recent taxonomic changes and this new addition. An updated dichotomous key for the genus is provided, incorporating all species described to date. These findings underscore the importance of exploring understudied marine habitats and highlight the potential for discovering more tardigrade species in Malaysia.

The caryophyllidean tapeworm Khawia armeniaca has long been regarded as an exceptionally widespread species within its genus, notable for its significant morphological variability. However, with the accumulation of molecular data from different fish hosts, K. armeniaca was suspected to represent a species complex. To clarify the true identity of these parasites, a comprehensive morphological and molecular study (using 18S, 28S and ITS2 ribosomal regions) of K. armeniaca tapeworms from barbels (Barbinae) across the Iberian Peninsula and the Middle East has been conducted. The results revealed two genetically distinct lineages within the K. armeniaca complex. The first lineage, found in Arabibarbus grypus, Barbus lacerta, Capoeta birunii, Carassobarbus luteus, Luciobarbus barbulus, L. esocinus and L. kersin in Iraq and Iran, is genetically congruent with K. armeniaca (Cholodkovsky, 1915), originally described from the Sevan khramulya (Capoeta sevangi) in Armenia. The second lineage, identified in Luciobarbus bocagei (type host), L. comizo and L. guiraonis from Portugal and Spain, is described as Khawia iberica n. sp. In addition to clear molecular divergence, K. iberica can be distinguished from K. armeniaca by notable morphological differences, including variations in the shape, structure and size of the ovary, the anterior extension of the vitelline follicles, the testes and several morphometric parameters.

Coastal ecosystems have been subject to anthropogenic environmental stressors. Although exposed to different environmental pressures and susceptible to bioinvasion events, Todos-os-Santos Bay (TSB) (12oS, Bahia State, Brazil) has great ecological importance. Among the bioinvasive organisms, Tubastraea corals (the ‘sun corals’) are widespread in artificial and natural environments of the TSB less frequently. Given the lack of baseline information characterizing the original biofouling communities, surveys approaching the malacofauna under the influence of sun corals are essential to the knowledge of local biodiversity and future losses due to possible environmental changes. To provide information on the diversity of the malacofauna, the gastropods, bivalves, and polyplacophorans in the presence of sun corals at 10 sampling stations in the TSB were investigated. Eighty-one taxa of different size classes (micro- and macromolluscs) and mobility (mobile and sessile) were recorded. These species belong to distinct trophic groups (carnivorous, herbivorous, grazers, parasites, and suspensivorous/passive filtering) and life modes (endolithic, epifauna, infauna, and ectoparasitic). Gastropoda had the highest number of species, followed by Bivalvia and Polyplacophora. Cerithiopsidae and Pyramidellidae were the most representative families. Three exotic species and seven new records were identified for the bay. The malacofauna associated with artificial substrates with the presence of sun coral proved to be complex and diverse.

Eels of the congrid genus Coloconger are rare and poorly known for their distributions. This study reports on the collection of the Indo-west Pacific short tail conger Coloconger scholesi Chan 1967 from Indian waters of the Arabian sea for the first time based on a single specimen collected from the deep waters off Kollam, Kerala and provides an additional report about Anguilliformes of India. Previously a single species of the genus Coloconger raniceps Alcock 1889 has been reported from Indian waters up to now. This study adds details about another Coloconger species, C. scholesi, a photograph of the specimen in fresh condition is provided, and comparison with its co-occurring in Indian waters congener C. raniceps is included.

Brittle stars undergo remarkable morphological changes during their transition to adulthood, extending beyond metamorphosis. Members of the genus Ophioderma exhibit particularly noteworthy morphological changes between the juvenile and adult stages. These growth changes have been a persistent source of misidentification in Ophioderma, even leading to the misclassification of juveniles to a different genus. In this study, the growth changes of three common eastern Pacific Ophioderma species were characterised: Ophioderma aija, Ophioderma occultum, and Ophioderma panamense. Their growth series, ranging from 2.5 to 26.7 mm disc diameter, were analysed by combining morphology, morphometrics, and DNA barcoding. Three size groups within the species were identified. In general, the morphological changes shown by the three species were highly similar and occurred at comparable sizes, allowing a pattern to be identified and reconstructed. However, differences between the species were observed throughout the series in quantitative (arm length, dorsal arm plates, number of arm spines) and qualitative (radial shields, colouration) characters. This work represents one of the few available contributions on the growth changes of Ophiuroidea from the eastern Pacific and so far in the genus Ophioderma.

Anthuroid isopods in the genus Mesanthura (52 valid species) typically have a body with conspicuous dorsal pigmentation, with differences in the female pigmentation pattern being one of the main characters used to distinguish species. Five Mesanthura species have been reported to date from Japan. Here, we describe Mesanthura sol sp. nov. from Irabu Island and Okinawa main island, Okinawa, Japan, and illustrate its sexual dimorphism in colour pattern, with conspecificity between males and females confirmed with molecular data. We provide a description of Mesanthura miyakoensis based on specimens collected from Kochi, Shikoku, Japan. We present the first records of Mesanthura cinctula and Mesanthura nigrodorsalis, following their original descriptions. Finally, we provide partial sequences of the 16S rRNA gene for these four species and present a phylogenetic tree based on the sequences.

Corticolous sorediate Candelariella represent, at least in Europe, a widespread group of species, often predominant in epiphytic communities. Many specimens are challenging to identify since apothecia are generally lacking and names have been frequently misapplied in the past. Here, we studied the morphology and molecular data (ITS nrDNA sequences) of corticolous sorediate Candelariella specimens, with the aim of determining how many species occur in Europe and which names should be applied. We distinguish worldwide five taxa from this group that are widespread and currently well supported by both morphological and molecular data. These include three 8-spored species (Candelariella reflexa, C. rubrisoli and C. xanthostigmoides) and two polyspored species (C. efflorescens and Candelariella pulchella sp. nov., the latter characterized by coarser soredia, larger apothecia with a persistent proper margin and broader paraphyses tips). Four of these species (all except C. xanthostigmoides) occur in Europe. European specimens previously identified as C. xanthostigmoides belong to C. rubrisoli. Candelariella makarevichiae and C. subsquamulosa are considered synonyms of C. xanthostigmoides. Candelariella sorediosa, C. flavosorediata and C. magellanica (the latter two not reported from Europe) remain poorly known species for which molecular data is currently lacking and they require further study. Full descriptions and a key to the species discussed are provided.

The description and delineation of trematode species is a major ongoing task. Across the field there has been, and currently still is, great variation in the standard of this work and in the sophistication of the proposal of taxonomic hypotheses. Although most species are relatively unambiguously distinct from their congeners, many are either morphologically very similar, including the major and rapidly growing component of cryptic species, or are highly variable morphologically despite little to no molecular variation for standard DNA markers. Here we review challenges in species delineation in the context provided to us by the historical literature, and the use of morphological, geographical, host, and molecular data. We observe that there are potential challenges associated with all these information sources. As a result, we encourage careful proposal of taxonomic hypotheses with consideration for underlying species concepts and frank acknowledgement of weaknesses or conflict in the data. It seems clear that there is no single source of data that provides a wholly reliable answer to our taxonomic challenges but that nuanced consideration of information from multiple sources (the ‘integrated approach’) provides the best possibility of developing hypotheses that will stand the test of time.

The present study describes a new Mediterranean terebellid, Spinosphaera latachaeta sp. nov., found along the Aegean coast of Türkiye and the Sea of Marmara, between 27 and 80 m depth in soft substrata. It can be morphologically distinguished from all other species of Spinosphaera having 18 pairs of notopodia, double rows of uncini present until the last notopodia, and 11 pairs of Spinosphaera-chaetae. A dichotomous taxonomic key and a table summarizing the morphological characters that distinguish all species of Spinosphaera are provided. This study also reports, for the first time, the transformations of Spinosphaera-chaetae and saw-like chaetae from the anterior to posterior segments of body.

ZooBank: urn:lsid:zoobank.org:pub:628B1F01-166A-4E26-9C42-39D0CBFDE998.

The brachyuran crab fauna (Crustacea: Decapoda: Brachyura) collections in the extensive exploratory fishery survey cruises from the northeast coast of India was studied from June 2018 to March 2020. During the study period, 81 species of brachyuran crabs belonging to 19 families and 46 genera were recorded. Among these, 21 species were newly recorded from the northeast coast of India, and 1 species, Naxioides taurus (Pocock, 1890) represents a new record for the mainland coasts of India. This study serves as a baseline for understanding the diversity and distribution of brachyuran crabs in the region. It provides valuable insights for future research and conservation efforts.

Gyalolechia fruticum, a new epiphytic species with a Mediterranean-Macaronesian distribution, is described. It differs in molecular data and in ecology from two closely related calcicolous species, G. luteococcinea and G. marmorata, both formerly called Caloplaca subochracea auct. The new species grows on coastal shrubs (rarely on wood), accompanied by species-rich communities of maritime epiphytic lichens. The typical habitat is undisturbed sand dunes, under dry conditions with frequent spells of humid air from the sea. The species is so far known from Greece, Italy, Tunisia, the Canary Islands and probably mainland Spain. We consider this conspicuous lichen an umbrella species of endangered and declining epiphytic communities of ancient shrub vegetation on well-developed sand dunes along Mediterranean coasts affected by touristic overexploitation.