Onthodiplogaster japonica n. gen., n. sp. (Rhabditida: Diplogastridae) isolated from Onthophagus sp. (Coleoptera: Scarabaeidae) from Japan

A diplogastrid nematode was isolated from a dung beetle, Onthophagus sp., collected from a rotten mushroom in Kyoto, Japan. The species is characterised by its cheilostomatal shape, separated into 12 narrow plates (rugae), deep stegostom, large ellipsoidal amphids, conical female tail and characteristic receptaculum seminis in the female. Based on its phylogenetic status and stomatal composition, the species is typologically similar to two other diplogastrid genera, Neodiplogaster and Mononchoides. The species can be distinguished from these two genera by the size and shape of the amphid (small pore in Neodiplogaster), female tail shape (long and filiform in Mononchoides) and presence of receptaculum seminis (absence in the two nominal genera), and is described as a monotypic member of a new genus, Onthodiplogaster japonica n. gen., n. sp. Observation of feeding behaviour suggested that O. japonica n. gen., n. sp. does not show clear stomatal dimorphism or polymorphism, which is found in its close relatives, but the species can feed on nematodes (predation), fungi and bacteria. This monomorphic omnivory possibly represents its habitat of dung and other rotten materials, where the environment is biologically divergent, and its condition changes rapidly.

Morphological and Molecular Characterization of Diplogasteroides sp., a Cryptic Population of the Haslacheri Group (Diplogastridae), and Parasitorhabditis terebranus (Rhabditidae) from Korea

Diplogasteroides sp., a cryptic population of D. haslacheri, and Parasitorhabditis terebranus were reported from the frass of Monochamus alternatus galleries in dead Pinus thunbergii for the first time in Korea. Females and males are morphologically characterized and their linked DNA barcodes (18S-rRNA, 28S-rRNA, ITS-rRNA and COI) supplied. Females and males of the two species from Korea conform to the original species descriptions from Europe and the USA, with variations in a few details in morphometrics. Specifically, Diplogasteroides sp. is morphologically very similar to D. haslacheri. However, it cannot be designated as D. haslacheri due to the existence of cryptic species complex within the haslacheri group (D. haslacheri, D. asiaticus, D. nix, D. andrassyi, and D. carinthiacus), a condition requiring hybridization studies to test species identity within the group. Based on analysis of COI sequences, differences among these cryptic species are evident. Thus, in addition to hybridization tests, the COI might be a powerful DNA barcoding marker for the precise identification of these cryptic species within the genus. Additionally, this is the first molecular characterization of P. terebranus, and the species is herein recorded for the first time outside its type locality.

New Records of Wood- and Bark-Inhabiting Nematodes from Woody Plants with a Description of Bursaphelenchus zvyagintsevi sp. n. (Aphelenchoididae: Parasitaphelenchinae) from Russia

Wood- and bark-inhabiting parasitic nematodes are of great economic importance. Nematodes can cause wilt diseases in conifers and deciduous trees. In 2014-2022, during nematology surveys conducted in different regions of Russia and Belarus, adults and dauer juveniles of nematodes were collected from wood, bark and beetle vectors. Using traditional morphological taxonomic characters integrated with molecular criteria, we identified in the studied samples the following nematode species: Aphelenchoides heidelbergi, Bursaphelenchus eremus, B. fraudulentus, B. michalskii, B. mucronatus, B. willibaldi, Deladenus posteroporus, Diplogasteroides nix and Laimaphelenchus hyrcanus, several unidentified species: Aphelenchoides sp.1 and sp.2, Cryptaphelenchus sp.1, sp.2 and sp.3, Laimaphelenchus sp.1, Micoletzkya sp.1, Parasitaphelenchus sp.1, Parasitorhabditis sp.1, three unidentified tylenchid nematodes and a new species, Bursaphelenchus zvyagintsevi sp.n. Morphological descriptions and molecular characterization are provided for B. zvyagintsevi sp. n. belonging to the Abietinus group and B. michalskii belonging to the Eggersi group. Findings of Aphelenchoides heidelbergi, Bursaphelenchus eremus, B. michalskii, Deladenus posteroporus, Diplogasteroides nix and Laimaphelenchus hyrcanus are new records for Russia. Phylogenetic positions of studied species were reconstructed using D2-D3 expansion segments of 28S rRNA gene sequence analysis. The data obtained in this study may help to detect the refugia of opportunistic plant pests and find possible native biocontrol nematode agents of insect vectors causing diseases.

Three Seinura species from Japan with a description of S. shigaensis n. sp. (Tylenchomorpha: Aphelenchoididae)

A preliminary survey of Seinura spp. was conducted in the Kyoto area, Western Japan. The survey yielded four new strains of Seinura spp., including two strains of S. caverna, a strain of S. italiensis, and a strain of an undescribed species. Molecularly, the two strains of S. caverna were nearly identical to the type strain but showed some minor variations, particularly in the mitochondrial cytochrome oxidase subunit I gene. The small subunit and D2-D3 large subunit sequences of the Japanese strain of S. italiensis were nearly identical and identical to its original description, respectively, and the difference in the small subunit was due to mis-reading of the sequences. The new species, S. shigaensis n. sp., was phylogenetically close to S. caverna and S. persica, although these three species were clearly different phylogenetically. The new species was typologically similar or nearly identical to several other Seinura spp., including S. chertkovi, S. christiei, S. italiensis, S. steineri, and S. tenuicaudata, but it can be distinguished from those species by the morphometric values. Because the new species is phylogenetically very close to S. caverna, it could be a good comparative system for S. caverna as a potential satellite model for the predatory nematode.

Morphological and molecular characterisation of Spirinia antipodea Leduc n. sp. (Nematoda: Desmodoridae), a cryptic species related to S. parasitifera, from the coast of New Zealand

Spirinia parasitifera is a common nematode species recorded from coastal habitats of the White, North and Barents Seas, the Northwest Atlantic, the Maldives and Australia, and exhibits a high degree of variability in some morphological characters. For these reasons it has been suggested that S. parasitifera is a species complex comprised of several distinct but potentially cryptic species. However, no study has yet combined molecular and morphological approaches to verify this assertion. Here, we describe S. antipodea n. sp., a species morphologically very similar to S. parasitifera, from the coast of New Zealand. Spirinia antipodea n. sp. differs from the original description of S. parasitifera as well as subsequent descriptions by other authors in at least one body dimension, but no single trait differs consistently between the New Zealand specimens and all descriptions of S. parasitifera. Phylogenetic analyses showed that the new species is distinct from other species of the genus, including S. parasitifera specimens sampled near the type locality. The S. antipodea n. sp. SSU sequence differed from other Spirinia sequence by 2.1-5.3%, whilst D2-D3 of LSU sequences differed by 12.5-18.9%. The consensus SSU tree also recovered three distinct S. parasitifera clades, which provides support for the existence of a species complex. Because it is not possible to determine whether the variability in morphological characters observed among descriptions of S. parasitifera is intra- or interspecific, and therefore to determine which trait can reliably be used to differentiate between S. antipodea n. sp. and S. parasitifera, the new species is best differentiated from S. parasitifera and other closely related species based on SSU sequences rather than morphological characters.

Acrostichus palmarum n. sp., a cryptic species separated from A. rhynchophori by molecular sequences and hybridisation tests

A new Acrostichus species is described based upon molecular sequence profiles and hybridisation testing. The new species, A. palmarum n. sp., had been previously described as local isolates (strains) of A. rhynchophori, i.e., an isolate recovered from Rhynchophorus cruentatus from South Florida (culture code RGD193) was designated as the type strain of A. rhynchophori, and other Central and South American strains (RGD194-196), recovered from R. palmarum were considered as conspecific regional isolates. However, additional sequencing of ribosomal DNA loci (near full-length of small subunit, full length of internal transcribed spacer and D2-D3 expansion segments of large subunit) and partial mitochondrial cytochrome oxidase subunit I gene and hybridisation testing suggested the independent species status of RGD194-196. Furthermore, two strains of A. palmarum n. sp., RGD194 and RGD195, showed partial reproductive isolation from each other, i.e., the fecundity of F1 progeny was obviously low, suggesting that geographical isolation within a widely-distributed species is occurring.

Sudhausia floridensis n. sp. (Nematoda: Diplogastridae) isolated from Onthophagus tuberculifrons (Coleoptera: Scarabaeidae) from Florida, USA

Sudhausia floridensis n. sp., a phoretic associate of a dung beetle, Onthophagus tuberculifrons, is described based on its typological characters and molecular profiles of part of the small subunit ribosomal RNA (rRNA) gene, D2-D3 expansion segments of the large subunit of rRNA gene, as well as part of the mitochondrial cytochrome oxidase subunit I (mtCOI) gene. Adult beetles collected from the cattle unit at the University of Florida, Gainesville, FL, USA were dissected and placed on a water agar plate to allow nematode propagation. The new species was isolated from a culture plate several weeks later, and subcultured to establish a laboratory strain. Sudhausia floridensis n. sp. is typologically very similar to S. aristotokia, but could be distinguished from it by the shape of the tail tip of the male, and presence vs absence of a terminal notch in the bursal velum. Molecularly, S. floridensis n. sp. is close to S. crassa, regardless of its morphological similarity to S. aristotokia, but it is distinguished from its African congeners S. aristotokia and S. crassa by 28 and 12 bp differences in SSU, respectively.