The study of the monogenean fauna of Brycinus kingsleyae, Brycinus macrolepidotus, Phenacogrammus major and Hepsetus odoe, four characiform fishes consumed in Cameroon allowed to find seven species of Annulotrema Paperna and Thurston, 1969 and provided new information for the diagnosis of these helminths. Concerning the parasites of Brycinus kingsleyae: in Annulotrema combesi Birgi, 1988, the copulatory tube can make two turns of spire contrary to the initial description which indicates a single turn; on the dorsal bar of Anulotrema maillardi Birgi, 1988, a sclerotized structure was observed for the first time; a loop was also noted for the first time on the ventral bar of Annulotrema nyongesnsis Birgi, 1988. For parasites of Phenacogrammus major, the vagina was observed for the first time in Annulotrema gabrioni Birgi, 1988. A membrane extension never reported on the dorsal transverse bar of Annulotrema hepseti Paperna and Thurston, 1969, a parasite of Hepsetus odoe was observed during this study. Principal Component Analysis (PCA) allowed the assignment of a morphogroup to the two recently described species in Brycinus macrolepidotus. Thus, a new morphogroup named Ngombiensis n. gr. was created to classify Annulotrema ngombiensis Ndongo and Tombi, 2023. As for Annulotrema nkengfacki Ndongo and Tombi, 2023, its morphometric characteristics allow it to be associated with the Nyongensis group created by Birgi in 1988.

Phytodietus (Weisia) clavotibialis Shimizu & Konishi, 2018 (Hymenoptera: Ichneumonidae: Tryphoninae: Phytodietini) is a rare and poorly known Darwin wasp, previously known only from the female holotype collected in Japan. In this study, the male is described for the first time based on two specimens. One of these was reared from a tortricid leaf-roller moth feeding on Rhododendron reticulatum D. Don ex G. Don, marking the first host record for both the species and the subgenus Weisia Schmiedeknecht from Tortricidae. New distribution records from India and Taiwan extend the known range of P. (W.) clavotibialis and reveal a biogeographic pattern resembling that of its closest relative, P. (W.) pitambari Kaur & Jonathan, 1979. Partial sequences of mitochondrial CO1 and nuclear 28S rDNA genes were newly obtained, representing the first molecular data for Weisia, and were used in a preliminary phylogenetic analysis. Although the subgenus Euctenopus Ashmead was not included in our analysis, the molecular phylogeny recovered Weisia as the most basal lineage within the genus Phytodietus Gravenhorst, supporting its recognition as a distinct subgenus, while the monophyly of the subgenera Phytodietus and Neuchorus Uchida was not supported. Given the longstanding confusion and our results, it is concluded that these subgenera are best treated as a single subgenus; thus, Neuchorus syn. nov., together with its previously recognized synonym Doratistes Seyrig, is synonymized under Phytodietus. Additionally, P. (W.) clavotibialis appears to be associated with secondary natural environments characteristic of Satoyama landscapes, raising conservation concerns due to ongoing habitat degradation.

The yellow bullhead, Ameiurus natalis (Lesueur) is a moderately-sized member of the catfish family Ictaluridae Gill with a fairly large North American distribution. Between March and December 2021 and again between March 2022 and March 2023, 37 A. natalis specimens were collected from watersheds in Arkansas (n = 30) and Oklahoma (n = 7), USA, and their gills, gallbladders, urinary bladders, fins, integument, other major organs, and musculature were examined for myxosporeans. The gallbladder of a single individual yellow bullhead from Sevier County, Arkansas, USA, was infected with a novel myxosporean, Myxidium horatioense n. sp. and an unknown species of myxosporean. Qualitative and quantitative morphological data were from ethanol-preserved myxospores of M. horatioense n. sp. Molecular data consisted of 1,846 and 844 base pair sequences of the partial small subunit ribosomal RNA gene for M. horatioense n. sp. and an unidentified myxosporean, respectively. This is the first report of any member of the genus Myxidium from A. natalis. This article was registered in the Official Register of Zoological Nomenclature (ZooBank) as urn:lsid:zoobank.org:pub:urn:lsid:zoobank.org:act:92DC4EB0-3590-4EE0-8D90-D1279C52763B.

This study presents morphological, molecular and phylogenetic analyses of two species of the genus Avitellina, A. sudanea and A. centripunctata parasitic in sheep and goats and sampled in the region of the City of Chandigarh, North India. Three molecular markers were used: mitochondrial cytochrome c oxidase subunit 1 (cox1), nuclear small subunit ribosomal RNA (SSU rDNA) and internal transcribed spacer 1-5.8S rRNA (ITS1-5.8S rDNA) genes. Morphological analysis revealed differences in key structures, including paruterine organ shape and testis arrangement. Molecular analysis revealed that A. sudanea showed no exact match but significant similarity with other species: A. lahorea and A. centripunctata, exhibiting 91.39% and 85.89-86.52% (SSU rDNA), 96.27 and 94.31% (cox1), 94.19 and 94.41% (ITS1-5.8S rDNA) sequence similarity, respectively. The Maximum Likelihood phylogenetic trees based on DNA sequences of SSU rRNA, cox1 and ITS1 placed these species in a separate clade, which was distinct from anoplocephalids (sensu stricto) and supported the thysanosomatids as a distinct taxon at the family level. The evolutionary divergence based on base substitution rates confirmed substantial interspecific genetic distinctions, with high divergence values of 0.12 (cox1), 0.25 (SSU rDNA) and 0.11 (ITS1-5.8S rDNA) between A. sudanea and A. centripunctata. This study provides the first molecular characterization of A. sudanea, confirming its genetic distinctiveness and taxonomic status as a valid species. Our findings highlight the necessity for more molecular studies on Avitellina tapeworms using robust genetic tools to ensure accurate taxonomic delineation within the genus.

Acanthocephalans collected from the stomach of the mackerel tuna (Euthynnus affinis Cantor) in the Persian Gulf off Iran were identified as Neorhadinorhynchus nudus Harada, 1938 based on morphological characters and molecular sequence data from mitochondrial (cytochrome c oxidase subunit I, COI) and nuclear ribosomal DNA (small and large subunit ribosomal DNA, 18S and 28S rDNA). Phylogenetic analyses of the order Echinorhynchida Southwell & Macfie, 1925 were performed based on the concatenated (18S+28S+COI) sequence data using maximum likelihood (ML) and Bayesian inference (BI) analyses. The results showed that N. nudus grouped together with species of Rhadinorhynchus Lühe, 1911, supporting the proposal that Neorhadinorhynchus Yamaguti, 1939 is a synonym of Rhadinorhynchus. Rhadinorhynchus mariserpentis Steinauer et al., 2019 was also treated as a junior synonym of Rhadinorhynchus nudus. Haplotype network analysis revealed no correlation between haplotype distribution and geographical origin of R. nudus.

Hysteromorpha Lutz, 1931 is a small but broadly distributed genus of diplostomoidean digeneans parasitic as adults primarily in cormorants, but also reported from some other fish-eating birds. Their metacercariae were found in a variety of freshwater fishes as second intermediate hosts. Prior to this study, the genus included only 3 nominal species, 2 of them distributed in the Old World and 1 in the New World. We obtained sequences of partial mitochondrial cox1 gene and nuclear rDNA operon from new specimens collected in Europe, North and South America and used them for species comparisons and phylogenetic analysis. We also examined morphology of our newly collected specimens as well as museum specimens. Our analysis has demonstrated that at least 2 (likely 3) species of Hysteromorpha are distributed in the Americas. Hysteromorpha sp. previously sequenced from larval stages, clearly represents a new species named herein Hysteromorpha ostrowskiaen. sp. Achatz, Locke et Tkach. Morphology of adults of the new species was earlier described in sufficient detail under the name Hysteromorpha triloba (Rudolphi, 1819). Our analyses also suggest the presence of another unknown Hysteromorpha sp. in North America represented by cox1 sequence from southeastern Canada (GenBank JF769473), but no morphological vouchers are available for this species.

This study describes Renicola websterae n. sp., a newly identified kidney fluke (Renicolidae: Trematoda) infecting two penguin species from New Zealand, the little blue penguin (Eudyptula novaehollandiae) and the Fiordland crested penguin (Eudyptes pachyrhynchus). Morphological and molecular analyses, including phylogenies based on cox1 and 28S genes, confirmed the distinctiveness of R. websterae. Key morphological features were discerned to be statistically comparable across five developmental stages, facilitating detailed characterization even in less mature specimens. A putative second, genetically distinct Renicola sp. was identified in Fiordland crested penguins and intermediate fish hosts, indicating a potential trophic link, and partly completing the known life cycle. We discuss the fact that kidney flukes have only been found in these two penguins and not in other New Zealand species, and the ecological and host-specificity factors likely influencing parasite distribution. This work represents the first record of a named Renicola species from New Zealand and only the second species found in penguins worldwide.

Cochimibdella mexicana n. gen. n. sp. is described based on morphological data and comparative analysis of DNA sequences, including two mitochondrial (cytochrome oxidase subunit I and 12s rRNA) and nuclear (18S rRNA and 28S rRNA) loci. Leech specimens were found in the mantle cavity and external surface of the octopus Octopus bimaculatus from Bahía de los Ángeles, Baja California, México. In vivo observations of recently hatched leeches in the laboratory confirm a broad prey range, including fishes, the most common hosts of the family species. The new taxon differs from species of the family Piscicolidae in possession of weakly developed tubercles in a3 of the urosome. In addition, molecular analysis places Cochimibdella mexicana n. gen. n. sp. sister to Austrobdella californiana and Myzobdella lugubris. This work amends a previous record of the elasmobranch-feeding leech Pontobdella (=Stibarobdella) moorei as a parasite of Octopus bimaculatus from the type locality of the new taxon.

A new ascaridoid nematode, Hysterothylacium malleocaudatum sp. n., was described using both light and scanning electron microscopy, based on specimens collected from the greater amberjack Seriola dumerili (Risso) (Carangiformes: Carangidae) in the Persian Gulf off Iraq. The new species can be distinguished from the congeners by the combination of the following features, the presence of remarkable lateral alae starting from base of ventro-lateral lips, the short intestinal caecum and long ventricular appendix (intestinal caecum representing 21.1-40.5% of oesophageal length, ratio of intestinal caecum to ventricular appendix 1: 1.42-3.77), the relatively long oesophagus (oesophageal length representing 9.83-14.3 % body length), the number and arrangement of the caudal papillae (31-37 pairs precloacal, 1-2 pairs paracloacal and 6 pairs postcloacal), and the presence of inflated hammer-shaped tail tip in both sexes. The new species represents the fourth Hysterothylacium species reported in marine fishes from Persian Gulf, off Iraq.

The familial affiliation of the so-far-monotypic palaeacanthocephalan genus Pseudocavisoma Golvan & Houin, 1964 has solely been based on morphological characteristics, lacking nucleotide sequence data. In this paper, we assess the phylogenetic position of the genus with a dataset consisting of partial sequences of the mitochondrial cytochrome c oxidase subunit I, and the nuclear 18S and 28S rRNA genes for 37 species of palaeacanthocephalans available in public databases along with the ones determined from the new species Pseudocavisoma setoensesp. nov., herein established with specimens collected from the intestine of the pearl-spot chromis Chromis notata (Temminck & Schlegel, 1843) obtained in the Seto Inland Sea, Japan. Our results suggested that Pseudocavisoma should be placed in Micracanthorhynchinidae Yamaguti, 1963, rather than in Cavisomatidae Meyer, 1932 as had been considered by previous authors. Because Micracanthorhynchinidae has been regarded synonymous with Rhadinorhynchidae Lühe, 1912 since 1985, we re-validate the former taxon while providing an amended diagnosis for it. Pseudocavisoma setoense sp. nov. can be distinguished from the sole congener Pseudocavisoma chromitidis (Cable & Quick, 1954) by the distributional pattern and the size of spines on the trunk. We provide a partial morphological redescription of the latter species based on syntypes of Cavisoma chromitidis Cable & Quick, 1954. We also provide an amended diagnosis for Pseudocavisoma to accommodate P. setoense sp. nov.