Schrével Joseph, Valigurová Andrea, Prensier Gérard, Chambouvet Aurélie, Florent Isabelle, Guillou Laure
Unité Molécules de Communication et Adaptation des Microorganismes, (MCAM, UMR 7245), Muséum National Histoire Naturelle, Sorbonne Universités, CNRS, CP 52, 57 Rue Cuvier, 75005 Paris, France.
Department of Botany and Zoology, Faculty of Science, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic.
Protist. 2016 Aug;167(4):339-368. doi: 10.1016/j.protis.2016.06.001. Epub 2016 Jun 18.
Archigregarines, an early branching lineage within Apicomplexa, are a poorly-known group of invertebrate parasites. By their phylogenetic position, archigregarines are an important lineage to understand the functional transition that occurred between free-living flagellated predators to obligatory parasites in Apicomplexa. In this study, we provide new ultrastructural data and phylogenies based on SSU rDNA sequences using the type species of archigregarines, the Selenidiidae Selenidium pendulaGiard, 1884. We describe for the first time the syzygy and early gamogony at the ultrastructural level, revealing a characteristic nuclear multiplication with centrocones, cryptomitosis, filamentous network of chromatin, a cyst wall secretion and a 9+0 flagellar axoneme of the male gamete. S. pendula belongs to a monophyletic lineage that includes several other related species, all infecting Sedentaria Polychaeta (Spionidae, Sabellaridae, Sabellidae and Cirratulidae). All of these Selenidium species exhibit similar biological characters: a cell cortex with the plasma membrane - inner membrane complex - subpellicular microtubule sets, an apical complex with the conoid, numerous rhoptries and micronemes, a myzocytosis with large food vacuoles, a nuclear multiplication during syzygy and young gamonts. Two other distantly related Selenidium-like lineages infect Terebellidae and Sipunculida, underlying the ability of archigregarines to parasite a wide range of marine hosts.
顶复门早期分支谱系中的原簇虫类是一类鲜为人知的无脊椎动物寄生虫。从系统发育位置来看，原簇虫类是理解顶复门中从自由生活的鞭毛虫捕食者到专性寄生虫这一功能转变的重要谱系。在本研究中，我们利用原簇虫类的模式种——1884年贾德命名的多钩原簇虫（Selenidium pendula），提供了基于小亚基核糖体DNA（SSU rDNA）序列的新超微结构数据和系统发育树。我们首次在超微结构水平描述了配对和早期配子发生过程，揭示了具有中心锥的特征性核增殖、隐有丝分裂、染色质丝状网络、囊壁分泌以及雄配子的9 + 0鞭毛轴丝。多钩原簇虫属于一个单系谱系，其中包括其他几个相关物种，它们均感染定居多毛纲动物（海稚虫科、缨鳃虫科、毛翼虫科和蛰龙介科）。所有这些原簇虫物种都表现出相似的生物学特征：具有质膜 - 内膜复合体 - 表膜下微管组的细胞皮层、具有类锥体、众多棒状体和微线体的顶复合器、带有大型食物泡的噬细胞作用、配对和年轻配子体时期的核增殖。另外两个远缘相关的类似原簇虫的谱系感染蛰龙介科动物和星虫动物门，这表明原簇虫类有寄生多种海洋宿主的能力。
