Bull. Natl. Mus. Nat. Sci., Ser. A, 43(1), pp. 1–28, February 22, 2017 Digeneans Parasitic in Freshwater Fishes (Osteichthyes) of Japan X. Opecoelidae, Plagioporinae Takeshi Shimazu 10486–2 Hotaka-Ariake, Azumino, Nagano 399–8301, Japan E-mail:
[email protected] (Received 24 November 2016; accepted 22 December 2016) Abstract This paper reviews species of the subfamily Plagioporinae Manter, 1947 in the family Opecoelidae Ozaki, 1925 (Trematoda, Digenea, Allocreadioidea) parasitic in freshwater fishes of Japan: four identified and one unidentified species of Neoplagioporus Shimazu, 1990, three identi- fied and one unidentified species of Urorchis Ozaki, 1927, and Opecoelidae gen. sp. of Shimazu (1990). Each species is described and figured. A neotype is designated for Podocotyle ayu Taka- hashi, 1928, or now Neoplagioporus ayu (Takahashi, 1928). The type host is Plecoglossus altivelis altivelis (Temminck and Schlegel, 1846) (Plecoglossidae), which was collected in the Asahi River at Takebe-cho (34°52′N, 133°54′E) (type locality), Kita-ku, Okayama City, Okayama Prefecture, Japan. A neotype is designated for Urorchis goro Ozaki, 1927. The type host is Tridentiger brevispinis Katsuyama, Arai, and Nakamura, 1972 (Gobiidae), which was collected in the Gantsu River at Yabata (36°0′N, 140°31′E) (type locality), Namegata City, Ibaraki Prefecture, Japan. The life cycle of U. goro is briefly mentioned. Morphological differences between Neoplagioporus and Urorchis are discussed. Keys to genera of the subfamily Plagioporinae in Japan and species of Neoplagioporus