Abstract：
In Japan, trematodes of the family Ochetosomatidae are not naturally distributed. However, the introduced ochetosomatid Ochetosoma kansense (Crow, 1913) has been reported from the oral cavity of native snakes in western Japan since 2010s. In this study, trematodes were isolated from the oral cavities of the native Japanese snakes, Elaphe quadrivirgata (Boie, 1826), E. climacophora (Boie, 1826), and Rhabdophis tigrinus (Boie, 1826), in the central Kanto region of eastern Japan. Morphological and molecular analyses of the isolated trematodes revealed that all trematodes were identifiable to a newly introduced ochetosomatid species to Japan, O. elongatum (Pratt, 1903), which originated from North America; Lechriorchis tygarti Talbot, 1933 was synonymized with O. elongatum based on identical molecular data and morphological similarity. To identify first intermediate hosts of O. elongatum, seven freshwater snail species were examined in eastern Japan. Molecular analysis was used to identify O. elongatum sporocysts in the freshwater snail Physella acuta (Draparnaud, 1805), which also originated from North America. The other six species did not host O. elongatum, suggesting that Ph. acuta is the only first intermediate host of O. elongatum in Japan. Although O. elongatum has been detected in Japan, its invasion route and period of introduction are unclear. Frequent imports of freshwater snails and wild snakes from North America, after the 1990s and 2005, respectively, presumably introduced O. elongatum in Japan.
摘要：
在日本,Ochetosomatidae科的吸虫不是自然分布的。然而,引入的Ochetosomakansense(Crow，自2010年以来，已从日本西部的本地蛇的口腔中报道了1913年。在这项研究中,吸虫是从日本本土蛇的口腔中分离出来的，Elaphequadrivirgata（Boie，1826),E.Cliacophora(Boie，1826),和Rhabdophistigrinus(Boie，1826),在日本东部的关东地区。对分离出的吸虫的形态和分子分析表明，所有吸虫都可以识别为新引入日本的卵裂虫。O.elongatum(Pratt,1903),起源于北美；Lechriorchistygarti基于相同的分子数据和形态相似性，与O.elongatum同义。为了识别O.elongatum的第一个中间宿主，在日本东部检查了7种淡水蜗牛。分子分析用于鉴定淡水蜗牛Physellaacuta（Draparnaud，1805),也起源于北美。其他六个物种不寄主O.elongatum，暗示Ph.acuta是日本唯一的O.elongatum的第一个中间宿主。尽管在日本发现了O.elongatum，其入侵路线和引入时期尚不清楚。经常从北美进口淡水蜗牛和野生蛇，分别在1990年代和2005年之后，大概是在日本引入了O.elongatum。
