Liang Li

Two nematode species parasitizing different developmental stages of the Indian rice frog Fejervarya kawamurai collected from Kasugai City, Japan, were examined using an integrative taxonomic approach combining morphology, scanning electron microscopy (SEM), and molecular analyses. Tadpoles of F. kawamurai were found to be infected exclusively by the oxyuroid nematode Gyrinicola japonicus , whereas adult frogs harboured a cosmocercoid nematode representing a new species of Cosmocerca , namely C. kasugaiensis n. sp. Detailed morphological observations revealed diagnostic characters of the new species, including the presence of well-developed lateral alae, equal spicules distinctly longer than the gubernaculum, five pairs of precloacal plectanes surrounded by incomplete circles of tubercles, and somatic papillae in both sexes. Molecular analyses based on nuclear 28S rDNA, internal transcribed spacer (ITS), and mitochondrial cox1 sequences showed no intraspecific variation among individuals of C. kasugaiensis n. sp., and consistently supported its distinctiveness from its congeners by Assemble Species by Automatic Partitioning (ASAP) and Bayesian inference analyses. The redescription of G. japonicus incorporates new features, including cephalic structures and egg morphological details revealed by SEM. This study also provides the ITS and cox 1 sequences for this species for the first time. Morphological and molecular analyses confirmed the distinct species position within Gyrinicola.

The genus Contracaecum is an important group of anisakid nematodes containing species of veterinary, medical, and economic importance. However, current genetic sequences and the mitogenomic database for Contracaecum spp. are limited. In the present study, the nuclear 18S, 28S, and ITS regions and the mitochondrial cox1 , cox2 , and 12S data for C. ovale (Linstow 1907) were sequenced based on the newly collected specimens from Tachybaptus ruficollis (Podicipediformes: Podicipedidae) in China. These sequences exhibited 100% similarity in the 18S and 28S regions and 99.8% similarity in the ITS-1 region (the presence of only a single locus of nucleotide polymorphism), compared with samples of Contracaecum ovale from Podiceps cristatus australis in New Zealand. Molecular analysis of two different individuals of C. ovale , collected from T. ruficollis in China, showed no genetic divergence with respect to the 18S, 28S, ITS, cox 1, and 12S regions, but a low level of divergence in the cox 2 sequences (0.73%). The complete mitogenome of C. ovale , presented for the first time, is 13,769 bp in length and includes 12 protein-coding genes, 22 tRNA genes, 2 ribosomal RNAs, and 2 non-coding regions. The mitogenome of C. ovale represents the smallest known anisakid mitogenome, and its overall A + T content (71.5%) is the highest level of A + T content of any anisakid. The mitogenomic phylogeny of those Contracaecum spp. whose mitochondrial protein-coding genes (PCGs) have been studied suggests that C. rudolphii and C. ogmorhini are more closely related to each other than either is to C. ovale. The genetic and mitogenomic data presented herein will be helpful for future studies on the population genetics and phylogenetics of Contracaecum spp.

Pinworms (Nematoda: Oxyurida) are among the first documented zooparasitic nematodes, and some species are of veterinary, medical, and economic importance. However, the basic molecular phylogenetic framework for the Oxyurida is far from comprehensive, and the origin and early evolutionary history of the group remain little understood. In this study, phylogenomic analyses of the Oxyurida, involving the most comprehensive family‐level taxon sampling of pinworms to date, were performed based on the universal single‐copy orthologues and the mitochondrial protein‐coding genes. Phylogenomic results yielded a highly resolved tree that confirmed the validity of the family Gyrinicolidae, suggested that the Heteroxynematidae is nested within the Oxyuridae and should be treated as a subfamily within the latter family (Heteroxynematinae status novus ), and failed to support the separation of the subfamilies Oxyurinae and Syphaciinae. Using fossil‐based time priors to calibrate both mitogenomic and genomic phylogenies, we establish the first comprehensive evolutionary timescale for pinworms. Our results place the most recent common ancestor of the Oxyurida in the late Devonian and further support the hypothesis that members of the vertebrate‐parasitic Oxyuroidea initially parasitized reptiles and later extended their host range to mammals, and during this transition, opportunistically produced a highly specialized lineage infecting anuran tadpoles.

The family Isthmosacanthidae is a group of acanthocephalans mainly parasitic in fishes of Osteichthyes. A new isthmosacanthid species, Gorgorhynchus fistularius sp. nov . (Polymorphida, Isthmosacanthidae) is described based on specimens collected from the red cornetfish Fistularia petimba (Lacépède, 1803) (Syngnathiformes, Fistulariidae) using the integrated morphological characters and molecular data. The complete mitochondrial genome of G. fistularius sp. nov . is presented, which is 14,409 bp in length and represents the first mitogenomic data for the genus Gorgorhynchus and also for the family Isthmosacanthidae. Comparative mitogenomic analysis revealed that the overall A+T content (68.1%) in the mitogenome of G. fistularius sp. nov . is distinctly higher than that of the other mitogenomes of the order Polymorphida reported so far (54.5‒64.4%), but the composition and gene rearrangement of the mitogenome of G. fistularius sp. nov . are identical to the current known mitogenomes of polymorphid species except for Southwellina hispida . Mitogenomic phylogenies supported the Isthmosacanthidae as a distinct family, and suggested new insights into the interfamilial relationships occurring as Plagiorhynchidae + [Isthmosacanthidae + (Centrorhynchidae + Polymorphidae)] in the order Polymorphida.

Acanthocephalans of the genus Rhadinorhynchus parasitize various marine fishes worldwide. However, the true diversity of Rhadinorhynchus is still unclear. In this study, we found an example of phenotypic variation in trunk spines of the poorly known rhadinorhynchid species R. cololabis Laurs & McCauley, 1964. According to the number and distribution of trunk spines, the present specimens of R. cololabis can be divided into two distinct morphotypes, which may erroneously be recognized as distinct taxa in the absence of molecular data. However, the Assemble Species by Automatic Partitioning (ASAP) and Bayesian inference (BI) analyses based on different nuclear and mitochondrial sequence data, all confirm that the two distinct morphotypes are conspecific, and do not represent two separate genetic lineages. Our ASAP and BI results of cox1 data also suggest that is R. villalobosi Martínez-Flores et al. , 2025 is a synonym of R. trachinoti Grano-Maldonado et al. , 2025, and challenge the validity of R. dorsoventrospinosus Amin et al. , 2011, and R. hiansi Soota & Bhattacharya, 1981. The present findings also indicate that the number and distribution of trunk spines vary markedly in some species of Rhadinorhynchus , and care must be taken when differentiating Rhadinorhynchus species based on this feature. Additionally, the complete mitogenome of R. cololabis is presented for the first time, which has only 13,567 bp, and displays a very high level of similarity with the mitogenome of R. laterospinosus in both nucleotide sequences (94.6%) and amino acid sequences of 12 protein-coding genes (93.8%). However, comparative mitogenomics support R. cololabis and R. laterospinosus representing two separate taxa.

Background: Nematodes of the order Spirurida are of significant veterinary, medical, and economic importance. However, current knowledge of the phylogenetic relationships within the order is far from comprehensive. Moreover, the monophyly of the Physalopteroidea/Physalopteridae, and the phylogenetic relationships of its three component subfamilies, remain uncertain due to inadequate sequence data. Methods: The nuclear small ribosomal subunit (18S rRNA) and large ribosomal subunit (28S rRNA), plus the complete mitochondrial genomes of two physalopterid species, Thubunaea pudica (Thubunaeinae) and Abbreviata varani (Physalopterinae), are presented for the first time. Phylogenetic analyses of the Spirurida were performed using maximum likelihood and Bayesian inference on the basis of different concatenated datasets involving the most comprehensive subfamily-level taxon sampling of the superfamily Physalopteroidea to date to provide an initial understanding of the evolutionary relationships of major superfamilies within the order, with special emphasis on the Physalopteroidea/Physalopteridae. Results: The complete mitogenomes of T. pudica and A. varani are 13,645 bp and 13,730 bp in length, which both contain 36 genes and belong to the GA9 type gene arrangement. Molecular phylogenies based on different datasets all support a close affinity between the superfamilies Camallanoidea and Dracunculoidea. Our phylogenetic results also showed that the representatives of the Physalopteridae did not form a monophyletic group. The representative of the subfamily Proleptinae clustered together with the tetramerid species Crassicauda magna , and the representative of the subfamily Thubunaeinae formed a sister relationship with species of the subfamily Physalopterinae. Conclusions: The mitogenome of T. pudica is the first for the subfamily Thubunaeinae, and that of A. varani is also the first for the genus Abbreviata . Molecular phylogenetic results suggest that the subfamily Proleptinae should be elevated to full family level, i.e., Proleptidae stat. nov., and that the genus Crassicauda (Habronematoidea: Tetrameridae) should be assigned to Proleptidae stat. nov. Our results also indicate that the Physalopteridae sensu stricto currently comprises two subfamilies, the Thubunaeinae and the Physalopterinae, and that the genus Skrjabinoptera should be transferred from the Physalopterinae to the Thubunaeinae. Graphical

The millipede order Spirostreptida (Arthropoda: Diplopoda) displays extremely high species diversity. However, the current classification of Spirostreptida is controversial, and the systematic status and phylogenetic relationships of some of its included superfamilies or families and genera remain uncertain due to the paucity and inaccessibility of suitable material or genetic data for key taxa. In the present study, a new pericambalid species, Pericambala foveiformis, sp. nov. (Cambalidea), is described using integrated methods. Moreover, the complete mitochondrial genomes of this new species and Agaricogonopus acrotrifoliolatus Zhang & Zhang, 1997, are sequenced and annotated. The mitogenome of P. foveiformis, sp. nov. is the first for the suborder Cambalidea, whereas that of A. acrotrifoliolatus is the first for the family Harpagophoridae. The mitogenome of P. foveiformis, sp. nov. with 17,467 bp in length, is the largest diplopod mitogenome currently known. Phylogenetic results based on the 16S rRNA (16S) + cox1 data and the concatenated amino acid sequences of 13 mitogenome protein-coding genes, both support the division of the order Spirostreptida into two suborders, Cambalidea and Spirostreptidea, but do not support the division of the suborder Spirostreptidea into two superfamilies Odontopygoidea and Spirostreptoidea, because of the two odontopygoid genera Chaleponcus and Prionopetalum nested within Spirostreptoidea. The phylogenetic analyses of 16S + cox1 data also show that Harpagophoridae and Pericambalidae are each monophyletic. However, the phylogenetic relationships among the three families Harpagophoridae, Odontopygidae and Spirostreptidae within Spirostreptidea remain unresolved. ZooBank: urn:lsid:zoobank.org:pub:A5A9F1D8-7958-4F72-9DD3-919B9304A03A

Background: The family Rhadinorhynchidae is a common group of acanthocephalans parasitizing various marine and freshwater fishes. The current knowledge of the pattern of mitogenomic evolution of the rhadinorhynchid acanthocephalans is still extremely limited. The monophyly of the Rhadinorhynchidae and the phylogenetic status of several of its included genera and subfamilies remain under debate. Methods: The complete mitogenomes of Micracanthorhynchina hemirhamphi and Rhadinorhynchus laterospinosus were sequenced and annotated for the first time on the basis of the specimens collected from the Asian pencil halfbeak Hyporhamphus intermedius (Cantor) (Beloniformes: Hemiramphidae) and the frigate tuna Auxis thazard (Lacepède) (Scombriformes: Scombridae), respectively. Phylogenetic analyses of Acanthocephala were performed on the basis of the concatenated amino acid sequences of 12 protein-coding genes (PCGs) of mitogenomes using maximum likelihood (ML) and Bayesian inference (BI), respectively. Results: The complete mitogenomes of M. hemirhamphi and R. laterospinosus are 17,272 bp and 13,567 bp in length, which both include 36 genes, containing 12 PCGs (missing atp8), 22 transfer RNA (tRNA) genes, and two ribosomal RNAs (rrnS and rrnL), plus two noncoding regions. Additionally, several tRNA gene rearrangement events occurred in the mitogenomes of both M. hemirhamphi and R. laterospinosus. Phylogenetic results supported the traditional rhadinorhynchid genus Micracanthorhynchina as a distinct lineage from Rhadinorhynchidae and Cavisomatidae. Conclusions: The mitogenome of M. hemirhamphi represents the largest mitogenome of acanthocephalan reported so far. The mitogenome of R. laterospinosus is the smallest mitogenome of the order Echinorhynchida, which also represents the first mitogenomic data for the genus Rhadinorhynchus and also for the Rhadinorhynchidae sensu stricto. Comparative mitogenomic analyses revealed the gene arrangements of R. laterospinosus and M. hemirhamphi represent two new types of mitochondrial gene arrangement reported in Acanthocephala. Moreover, mitogenomic phylogenies further confirmed the validity of the family Micracanthorhynchinidae and suggested a sister relationship Micracanthorhynchinidae + (Rhadinorhynchidae + Cavisomatidae) within Echinorhynchida. Graphical Created in BioRender. Hardy, H. (2025) https://BioRender.com/mo3g1wr