Graduate School of Science, Hokkaido University, N10W8, Sapporo, 060-0810, Japan.
Pathology Division, Nansei Field Station, Japan Fisheries Research and Education Agency, Fisheries Technology Institute, 422 1, Nakatsuhamaura, Minami Ise, Watarai, Mie, 516-0193, Japan.
Acta Parasitol. 2024 Sep;69(3):1411-1425. doi: 10.1007/s11686-024-00876-1. Epub 2024 Aug 10.
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.
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.
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.
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.
分子系统发育学提高了棘头动物系统分类学的水平，但仍有许多类群尚未得到探索。古棘头虫属 Metarhadinorhynchus Yamaguti, 1959 及其模式种 M. lateolabracis Yamaguti, 1959 就是这样有待探索的类群。我们旨在（i）完善系统定位，（ii）形态学定义，以及（iii）属的分类成分。我们还旨在检查被归入该属的物种的分类地位。
对新采集的标本以及 Metarhadinorhynchus lateolabracis 的模式标本进行了形态学观察。此外，还基于新采集的标本进行了最大似然法和贝叶斯推断的分子系统发育分析。根据文献资料，对至少一次被归入 Metarhadinorhynchus 的命名种以及相关形式 Gorgorhynchus lateolabri Yin 和 Wu, 1984 进行了重新评估。
我们对 M. lateolabracis 模式标本的重新检查表明，其水泥腺的数量为 6 个，而不是原始描述和插图中描述的 8 个。在得到的系统发育树上，M. lateolabracis 被嵌套在 Isthmosacanthidae 中。Gorgorhynchoides Cable 和 Linderoth, 1963 被发现是 Metarhadinorhynchus 的次异名。对曾被归入 Metarhadinorhynchus 的六个命名种的分类学重新评估，导致了对 Indorhynchus Golvan, 1969 和 Neotegorhynchus Lisitsyna, Xi, Orosová, Barčák, and Oros, 2022 的属诊断的修改。
Metarhadinorhynchus 被归入 Leptorhynchoididae（Echinorhynchida），但我们的研究现在将其归入 Isthmosacanthidae（Polymorphida）。我们在 Metarhadinorhynchus 中提出了 13 个新的特定名称的组合，在 Indorhynchus 中提出了 3 个。Metarhadinorhynchus lateolabri (Yin and Wu, 1984) comb. nov. 可能与 M. orientalis (Wang, 1966) comb. nov. 同义。
