Iritani Davis, Wakeman Kevin C, Leander Brian S
Department of Botany and Zoology, University of British Columbia, #3529 - 6270 University Blvd., Vancouver, BC, V6T 1Z4, Canada.
Office of International Affairs, Hokkaido University, North 10, West 8, Sapporo, 060-0810, Japan.
J Eukaryot Microbiol. 2018 Mar;65(2):211-219. doi: 10.1111/jeu.12462. Epub 2017 Sep 8.
Gregarine apicomplexans are unicellular parasites commonly found in the intestines and coeloms of invertebrate hosts. Traits associated with the conspicuous feeding stage of gregarines, known as the trophozoite, have been used in combination with molecular phylogenetic data for species delimitation and the reconstruction of evolutionary history. Trophozoite morphology alone is often inadequate for inferring phylogenetic relationships and delimiting species due to frequent cases of high intraspecific variation combined with relatively low interspecific variation. The current study combined morphological data with small subunit (SSU) rDNA sequences to describe and establish two novel marine gregarine species isolated from the intestine of a polychaete host Lumbrineris inflata collected in British Columbia (Canada): Paralecudina anankea n. sp. and Lecudina caspera n. sp. The sister species to the host is Lumbrineris japonica, which can be found on the opposite side of the Pacific Ocean (Japan) and contains two different species of gregarine parasites: Paralecudina polymorpha and Lecudina longissima. Molecular phylogenetic analyses placed P. anankea n. sp. as the sister species to P. polymorpha and L. caspera n. sp. as the sister species to L. longissima. This phylogenetic pattern demonstrates a co-evolutionary history whereby speciation of the host (Lumbrineris) corresponds with simultaneous speciation of the two different lineages of intestinal gregarines (Paralecudina and Lecudina).
簇虫纲顶复门原虫是常见于无脊椎动物宿主肠道和体腔中的单细胞寄生虫。与簇虫显著摄食阶段（即滋养体）相关的特征，已与分子系统发育数据结合起来用于物种界定和进化历史的重建。仅滋养体形态往往不足以推断系统发育关系和界定物种，因为种内变异高而种间变异相对低的情况屡见不鲜。本研究将形态学数据与小亚基（SSU）核糖体DNA序列相结合，以描述并确立从加拿大不列颠哥伦比亚采集的多毛纲宿主肥胖索沙蚕肠道中分离出的两种新型海洋簇虫：异形拟勒克簇虫（Paralecudina anankea）新种和卡斯佩勒克簇虫（Lecudina caspera）新种。宿主的姊妹物种是日本索沙蚕，它见于太平洋对岸（日本），并包含两种不同的簇虫寄生虫：多形拟勒克簇虫和长形勒克簇虫。分子系统发育分析将异形拟勒克簇虫新种置于多形拟勒克簇虫的姊妹物种位置，将卡斯佩勒克簇虫新种置于长形勒克簇虫的姊妹物种位置。这种系统发育模式显示了一种共同进化历史，即宿主（索沙蚕属）的物种形成与肠道簇虫的两个不同谱系（拟勒克簇虫属和勒克簇虫属）的同时物种形成相对应。
