Acanthocephalan parasites collected from Austrian fishes: molecular barcoding and pathological observations

Molecular Systematics and Type-material-based Redescription of Metarhadinorhynchus lateolabracis, With Taxonomic Revisions of Metarhadinorhynchus, Indorhynchus, and Neotegorhynchus (Acanthocephala: Palaeacanthocephala)

PURPOSE

Molecular phylogenetics has been improving the acanthocephalan systematics, yet numerous taxa remain unexplored. The palaeacanthocephalan Metarhadinorhynchus Yamaguti, 1959 and its type species M. lateolabracis Yamaguti, 1959 are such to-be-explored taxa. We aim to refine (i) the systematic placement, (ii) the morphological circumscription, and (iii) the taxonomic components of the genus. We also aim to examine the taxonomic status of the species that have been assigned to the genus.

METHODS

Morphological observations on newly collected specimens as well as the type material of Metarhadinorhynchus lateolabracis were conducted. Also, molecular phylogenetic analyses with maximum-likelihood method and Bayesian inference were performed based on freshly collected specimens. Nominal species that have at least once been assigned in Metarhadinorhynchus, as well as a related form, Gorgorhynchus lateolabri Yin and Wu, 1984, are taxonomically re-evaluated based on literature information.

RESULTS

Our re-examination of the type material of M. lateolabracis revealed that the number of cement glands is six, instead of eight as described and illustrated in the original description. In the resulting phylogenetic tree, M. lateolabracis was nested in Isthmosacanthidae. Gorgorhynchoides Cable and Linderoth, 1963 was found to be a junior synonym of Metarhadinorhynchus. Taxonomic re-evaluations of six nominal species that have once belonged in Metarhadinorhynchus led to modifications of generic diagnoses for Indorhynchus Golvan, 1969 and Neotegorhynchus Lisitsyna, Xi, Orosová, Barčák, and Oros, 2022.

CONCLUSIONS

Metarhadinorhynchus has been assigned to Leptorhynchoididae (Echinorhynchida), but our study now locates it in Isthmosacanthidae (Polymorphida). We propose 13 new combinations of specific names in Metarhadinorhynchus and three in Indorhynchus. Metarhadinorhynchus lateolabri (Yin and Wu, 1984) comb. nov. may be synonymous with M. orientalis (Wang, 1966) comb. nov.

A DNA barcode library of Austrian geometridae (Lepidoptera) reveals high potential for DNA-based species identification

Situated in the Eastern section of the European Alps, Austria encompasses a great diversity of different habitat types, ranging from alpine to lowland Pannonian ecosystems, and a correspondingly high level of species diversity, some of which has been addressed in various DNA barcoding projects. Here, we report a DNA barcode library of all the 476 species of Geometridae (Lepidoptera) that have been recorded in Austria. As far as possible, species were sampled from different Austrian regions in order to capture intraspecific genetic variation. In total, 2500 DNA barcode sequences, representing 438 species, were generated in this study. For complete coverage of Austrian geometrid species in the subsequent analyses, the dataset was supplemented with DNA barcodes from specimens of non-Austrian origin. Species delimitations by ASAP, BIN and bPTP methods yielded 465, 510 and 948 molecular operational taxonomic units, respectively. Congruency of BIN and ASAP partitions with morphospecies assignments was reasonably high (85% of morphospecies in unique partitions), whereas bPTP appeared to overestimate the number of taxonomic units. The study furthermore identified taxonomically relevant cases of morphospecies splitting and sharing in the molecular partitions. We conclude that DNA barcoding and sequence analysis revealed a high potential for accurate DNA-based identification of the Austrian Geometridae species. Additionally, the study provides an updated checklist of the geometrid moths of Austria.

Morphological and molecular characterization of a new species of the genus Echinorhynchus Zoega in Müller, 1776 (Acanthocephala: Echinorhynchidae) parasitizing the rock greenling Hexagrammos lagocephalus (Pallas) (Scorpaeniformes: Hexagrammidae) from eastern Hokkaido, Japan

A new species of marine-fish-parasitizing echinorhynchid palaeacanthocephalan, Echinorhynchus sasakiae sp. nov., is described based on material from the intestine of the rock greenling Hexagrammos lagocephalus (Pallas) obtained in two localities (Akkeshi and Nemuro) in Hokkaido, northern Japan. Echinorhynchus sasakiae sp. nov. can be distinguished from other congeners by having an oval-shaped proboscis covered with hooks arranged in 14-15 rows, each consisting of 7-10 hooks that are anteriorly short and curved, but posteriorly long and weakly curved. The phylogenetic position of Echinorhynchus sasakiae sp. nov. is inferred based on three gene markers (cytochrome c oxidase subunit I, 18S rRNA, and 28S rRNA) along with relevant sequences from ten congeners available in public databases. Echinorhynchus sasakiae sp. nov. represents the 54th member of the genus and the ninth marine congener known from Japan.

Systematic position of the genus Metacanthocephalus Yamaguti, 1959 (Palaeacanthocephala: Echinorhynchida) inferred from molecular evidence, with a redescription of Metacanthocephalus ovicephalus (Zhukov, 1960)

The familial affiliation of the echinorhynchid palaeacanthocephalan genus Metacanthocephalus has been uncertain, with the three families Echinorhynchidae, Leptorhynchoididae, and Rhadinorhynchidae having been suggested as its parent taxon. In this study, adult individuals of Metacanthocephalus ovicephalus from the intestine of the cresthead flounder Pseudopleuronectes schrenki (new host) and the dark flounder Pseudopleuronectes obscurus in Hokkaido, Japan, were examined. Using three gene markers (mitochondrial cytochrome c oxidase subunit I; nuclear 18S and 28S rRNA genes) determined from two specimens of M. ovicephalus, a molecular phylogenetic analysis was performed along with relevant sequences available in public databases representing 26 species in eight families of the order Echinorhynchida, along with five species from Polymorphida and two from Eoacanthocephala. The resulting phylogram showed that M. ovicephalus was nested within a clade along with nine species in eight genera (Brentisentis yangtzensis, Dentitruncus truttae, Dollfusentis bravoae, Koronacantha mexicana, K. pectinaria, Leptorhynchoides thecatus, Neotegorhynchus cyprini, Pseudoleptorhynchoides lamothei, and Tegorhynchus [= Illiosentis] sp.). In this paper, we propose i) a set of morphological characters to circumscribe members represented by this clade as a Linnaean higher taxon, ii) to place this taxon at the rank of family, iii) to refer to it as Leptorhynchoididae, and iv) to regard Illiosentidae as a junior synonym of Leptorhynchoididae. Our morphological examination revealed a single vaginal sphincter in M. ovicephalus, a character that was not mentioned in any of the previous literature. By this character, along with geographical distribution and host fish, six congeners currently recognized in Metacanthocephalus can be divided into two groups.