Everlasting Nature of Asia (ELNA), Ogasawara Marine Center, Ogasawara, Tokyo 100-2101, Japan.
Laboratory of Parasitology, Faculty of Veterinary medicine, Okayama University of Science, 1-3 Ikoinooka, Imabari 794-8555, Japan.
Parasitol Int. 2021 Aug;83:102377. doi: 10.1016/j.parint.2021.102377. Epub 2021 May 7.
Trematodes of the genus Rhytidodoides are parasitic in marine turtles. Of the already known species, Rhytidodoides similis Price, 1939, occurs especially in the gall bladder. In this study, we surveyed 73 green sea turtles (Chelonia mydas) in the Ogasawara Islands, Japan, and detected Rhytidodoides sp. from the gall bladders of 18 turtles. A detailed morphological analysis revealed that the forebody of Rhytidodoides sp. differed slightly in shape from that of R. similis. There has been no information on DNA sequences of the family Rhytidodidae. A molecular phylogeny based on 28S rDNA sequences of Rhytidodoides sp. and related taxa suggested that the Rhytidodidae is sister to the other families of Echinostomatoidea. The intraspecific diversity of Rhytidodoides sp. was examined by using DNA sequences of mitochondrial cytochrome c oxidase subunit 1 gene (COI). The population genetic features of the COI haplotypes demonstrated that Rhytidodoides sp. is highly diverse in the Ogasawara Islands. The DNA sequences determined in this study will contribute to the species identification of congeners and the taxonomic reconsideration of the Echinostomatoidea.
棘口科 Rhytidodoides 的吸虫寄生在海洋龟类中。已知的物种中，1939 年由 Price 命名的 Rhytidodoides similis 尤其存在于胆囊中。在这项研究中，我们调查了日本小笠原群岛的 73 只绿海龟（Chelonia mydas），并从 18 只海龟的胆囊中检测到 Rhytidodoides sp.。详细的形态分析表明，Rhytidodoides sp. 的前身形状与 R. similis 略有不同。关于棘口科的 DNA 序列还没有信息。基于 Rhytidodoides sp. 和相关分类群的 28S rDNA 序列的分子系统发育表明，棘口科与其他后睾科具有姐妹关系。通过线粒体细胞色素 c 氧化酶亚基 1 基因（COI）的 Rhytidodoides sp. 的种内多样性进行了检验。COI 单倍型的种群遗传特征表明，Rhytidodoides sp. 在小笠原群岛具有高度多样性。本研究中确定的 DNA 序列将有助于同属种的物种鉴定和后睾科的分类学再思考。
