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.