Shiozaki Akira, Amano Masao, Fernández Mercedes, Fraija-Fernández Natalia
Marine Mammal Research Laboratory, Graduate School of Fisheries Science and Environmental Sciences, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki 852-8521, Japan.
Marine Zoology Unit, Cavanilles Institute of Biodiversity and Evolutionary Biology, Science Park, University of Valencia, Catedrático José Beltrán 2, 46980 Paterna, Spain.
J Vet Med Sci. 2019 Apr 16;81(4):601-607. doi: 10.1292/jvms.18-0636. Epub 2019 Feb 25.
Synthesium elongatum (Brachycladiidae) is an intestinal digenean described from the finless porpoise (Neophocaena asiaeorientalis) in Japan. Few records of this species exist and there is a remarkable morphological similarity between S. elongatum and S. tursionis, such that a synonymy between the species has been suggested previously. However, no morphological and/or molecular analysis has been carried out to clarify the taxonomic status of S. elongatum. In this study, we collected specimens of Synthesium sp. from N. asiaeorientalis in western Japan. The specimens possess lobed testes within the third quarter of the body, a round ovary, and vitellaria extending to level of uterine field, which are diagnostic characters for both S. elongatum and S. tursionis. They were morphologically identified to S. elongatum or S. tursionis due to the fact that the available morphometric data for both species overlap remarkably. A molecular analysis of the mitochondrial ND3 gene showed that the pairwise nucleotide distances between these specimens and S. tursionis were small, and phylogenetic analysis showed that these specimens and S. tursionis are in the same clade. Therefore, it was indicated that S. elongatum and S. tursionis are the same species and, consequently, S. elongatum is a synonym of S. tursionis.
长形合盘吸虫（短腺科）是一种肠道复殖吸虫，最初是在日本的江豚（窄脊江豚）体内发现并记述的。关于该物种的记录很少，而且长形合盘吸虫和图氏合盘吸虫在形态上极为相似，因此之前有人提出这两个物种可能是同物异名。然而，此前尚未进行形态学和/或分子分析来明确长形合盘吸虫的分类地位。在本研究中，我们从日本西部的窄脊江豚体内采集了合盘吸虫属的标本。这些标本在虫体的前三分之一处有分叶状睾丸、圆形卵巢以及延伸至子宫区水平的卵黄腺，这些特征是长形合盘吸虫和图氏合盘吸虫的诊断特征。由于这两个物种现有的形态测量数据有显著重叠，所以从形态学上鉴定这些标本为长形合盘吸虫或图氏合盘吸虫。对线粒体ND3基因的分子分析表明，这些标本与图氏合盘吸虫之间的成对核苷酸距离很小，系统发育分析表明这些标本和图氏合盘吸虫属于同一分支。因此，表明长形合盘吸虫和图氏合盘吸虫是同一物种，所以长形合盘吸虫是图氏合盘吸虫的同物异名。
