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.

Morphological and genetic analyses were performed on seven species of the family Capillariidae (Nematoda: Trichocephalida: Trichinelloidea), viz. Eucoleus perforans, Eucoleus contortus, Aonchotheca bursata, Baruscapillaria obsignata, Capillaria anatis, Capillaria phasianina, and Capillaria spinulosa, detected in poultry from Japan and Indonesia. Two Eucoleus spp., perforating the esophageal mucosa of the Japanese green pheasant farmed in Japan (E. perforans) and domestic goose in Indonesia (E. contortus), were morphologically characterized. Furthermore, we observed substantial nucleotide differences between their 18S ribosomal RNA gene (rDNA), revealing maximum identity (97.27%) over the 1797-bp length. Similarly, B. obsignata in the small intestine of Japanese green pheasants in Japan, a chicken, geese, domestic pigeons, and a turkey in Indonesia, and C. anatis in the ceca of chickens in Indonesia were morphologically and molecular-genetically compared with previously reported isolates of these species in Japan. Aonchotheca bursata collected from the small intestine of the Japanese green pheasant was also molecular-genetically characterized for the first time; however, sequencing of the 18S rDNA of C. phasianina from the cecum of the same bird was unsuccessful. Capillaria worms in the ceca of a domestic duck and geese in Indonesia were identified as C. spinulosa, which had only previously been recorded in wild birds of the Anseriformes in the Palaearctic region. Morphologically, this species was closest to Capillaria pudendotecta recorded from the ceca of wild and captive swans, except for the lack of vaginal appendages in female worms and shorter esophagi relative to the body length in both male and female worms. Phylogenetically, these two species were closely related, although substantial nucleotide changes were noted. The 18S rDNA nucleotide sequences of the species isolated here were consistent with the recent taxonomic system established for Capillariidae based primarily on the morphology of male caudal ends.

An unexpected case of a Japanese wild boar (Sus scrofa leucomystax) infected with the giant thorny-headed worm (Macracanthorhynchus hirudinaceus) on the mainland of Japan (Honshu).

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.

Morphological and molecular genetic characterization of Kudoa konishiae n. sp. (Myxosporea: Multivalvulida) in the muscle of Japanese Spanish mackerel (Scomberomorus niphonius).

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.