Integrated taxonomic approaches to seven species of capillariid nematodes (Nematoda: Trichocephalida: Trichinelloidea) in poultry from Japan and Indonesia, with special reference to their 18S rDNA phylogenetic relationships

The giant thorny-headed worm Macracanthorhynchus hirudinaceus is a zoonotic acanthocephalan species with a worldwide distribution. Its natural definitive hosts are primarily pigs and wild boars (Sus scrofa), and scarabaeid beetles serve as the intermediate host. To date, there has only been one record of this acanthocephalan in Japan: a Ryukyu wild boar (Sus scrofa riukiuanus) hunted in 1973 on Amami Island, faraway from the Japanese mainland. The present study reports the second case of this acanthocephalan in Japan: a Japanese wild boar (Sus scrofa leucomystax) hunted in May 2017 in Yamaguchi Prefecture, the westernmost part of the Japanese mainland (Honshu). More than a dozen acanthocephalans (123 to 233 mm in length and 5 to 6 mm in width) were found with their proboscides inserted deeply into the intestinal wall, forming grossly visible nodules on the external surface. Isolated worms underwent a molecular genetic characterization of the ribosomal RNA gene (rDNA) and mitochondrial cytochrome c oxidase subunit 1 gene (cox-1). Long rDNA nucleotide sequences (5870 to 5890 bp) spanning the beginning of the 18S rDNA through to the 28S rDNA, including the internal transcribed spacer regions, and 1384-bp cox-1 nucleotide sequences were obtained. In the future, in conjunction with the accumulation of molecular genetic data of multiple M. hirudinaceus isolates from different endemic localities abroad, our data may help to postulate the origin or present transmission status of this extremely rarely encountered acanthocephalan in Japan.

The Japanese Spanish mackerel (Scomberomorus niphonius; Perciformes: Scombridae) is widely distributed in the continental shelves of the northwestern Pacific Ocean around Japan, Sea of Japan, and East China Sea. In the present study, small, spindle-shaped myxosporean plasmodia (0.15-0.53 mm by 0.04-0.13 mm) were frequently encountered in the myofiber of trunk muscles of two Japanese Spanish mackerels; one fished in the Sea of Japan off western Japan and the other in the northwestern Pacific Ocean off southern Japan in the autumn of 2016. Isolated myxospores of Kudoa konishiae n. sp. (Myxosporea: Multivalvulida) from these two fish were stellate with six equal shell valves and polar capsules, 8.1-9.7 μm in width, 7.1-8.8 μm in thickness, and 7.1-8.8 μm in length. The polar capsules were teardrop-shaped, 2.7-4.7 μm by 1.2-2.5 μm. The lateral view of spores revealed a drawstring-pouch shape. The nucleotide sequences of the 18S and 28S ribosomal RNA gene (rDNA) were distinct from any recorded species. Phylogenetic trees demonstrated a close relationship of the present new species with Kudoa spp. with stellate spores with five or more shell valves/polar capsules, recorded in scombrid fishes. To clarify the phylogenetic relationships between three closely related species, i.e., Kudoa konishiae n. sp., Kudoa hexapunctata, and Kudoa neothunni, three mitochondrial DNA genes (cytochrome c oxidase subunit 1 gene (cox-1) and the small and large subunits of the ribosomal RNA gene (rns-rnl)) of two isolates of the new species, six isolates of K. hexapunctata, and 13 isolates of K. neothunni were sequenced. The interspecific and intraspecific variations of the newly obtained cox-1 and rns-rnl nucleotide sequences of K. hexapunctata, K. neothunni, and K. konishiae n. sp. were clarified for the first time.

The naturalization of alien Reeves's muntjacs (Muntiacus reevesi) on Izu-Oshima Island, Tokyo, Japan, has proceeded intensively over the last five decades. To clarify whether the gastrointestinal helminths of these animals were brought from their original endemic area or were newly acquired in Japan, 32 Reeves's muntjacs trapped on the island were parasitologically examined. In addition to Gongylonema pulchrum in the oesophagus (34.4% prevalence), Chabaudstrongylus ninhae (Dróżdż, 1967) (Trichostrongylidae: Cooperiinae) and Oesophagostomum muntiacum Jian, 1989 (Chabertiidae: Oesophagostominae) were prevalent in the small (28.1%) and large (46.9%) intestines, respectively. For the first time, these trichostrongylid or chabertiid worms were genetically characterized based on partial nucleotide sequences of the nuclear ribosomal RNA gene (rDNA) and mitochondrial DNA cytochrome c oxidase subunit 1 gene (cox-1), and the phylogenetic relationships with other members of their family were explored. Since these two intestinal nematode species are inherent in muntjacs, this study demonstrates a new distribution of exotic helminth species in Japan in accordance with the naturalization of alien mammalian hosts. The molecular genetic data collected here could assist the taxonomic assessment of morphological variants in different Muntiacus spp. and/or of different geographical origins. Furthermore, our data may help to define the phylogenetic relationships among such isolates.