Taxonomic status of Fasciola in Japan : Comparison of mitochondrial NDI and COI sequences and ribosomal ITS2 sequence with Fasciola hepatica and Fasciola gigantica

本研究的目的是比较不同种间片吸虫线粒体NDI、COI和核糖体ITS2的核苷酸序列，并检测日本三倍体片吸虫的DNA多态性。限制性片段长度多态性分析表明，三倍体日本片吸虫至少由两个线粒体DNA类型的种群组成，这两个种群的三倍体日本种的母源可能不是肝片吸虫，而是巨大片吸虫。三倍体日本种和二倍体韩国种的一个种群都是单性生殖后代，可能起源于同一祖先巨尾扇贝。日本三倍体片吸虫的ND1和COI序列与巨型肝片吸虫的ND1和COI序列基本一致，但与肝片吸虫的ND1和COI序列不同。因此，日本的三倍体片吸虫被认为是大片吸虫。日本三倍体虫的ITS-2序列分为两种不同的类型，一种与印尼的肝片吸虫几乎完全相同，另一种与印度尼西亚的大片吸虫几乎完全相同。

The purpose of the study is to compare nucleotide sequences of mitochondrial NDI and COI and ribosomal ITS2 among Fasciola species, and to detect DNA polymorphism within triploid form of Fasciola in Japan. The analysis of restriction fragment length polymorphism shows that triploid Japanese Fasciola species is composed of at least two populations possessing respective type of mitochondrial DNA.It is probable that maternal origin of triploid Japanese species of the two populations is not F.hepatica, but rather F.gigantica. The one population of triploid Japanese species and diploid Korean species, both reproducing off spring parthenogenetically, would originate from the same ancestral F.gigantica. The ND1 and COI sequences of Japanese triploid forms of Fasciola were nearly identical to those found in F.gigantica, but were different from those of F.hepatica. Thus, the Japanese triploid forms of Fasciola are thought to be categorized to F.gigantica. The ITS-2 sequences of the Japanese triploid worms were divided into two distinct types, one of which was almost identical to that of F.hepatica and the other to F.gigantica from Indonesia.