CNRS, UMR 7144 & Université Pierre et Marie Curie, Station Biologique de Roscoff, Equipe EPPO-Evolution du Plancton et PaléoOcéans, Place Georges Teissier, 29682 Roscoff, France.
Protist. 2010 Jul;161(3):385-99. doi: 10.1016/j.protis.2010.01.002. Epub 2010 Feb 11.
The taxonomic status of the free-living stage of the dinoflagellate Gymnodinium béii, symbiont of the foraminifer Orbulina universa, was reassessed on the basis of detailed morpho-genetic analyses. Electron microscopy observations revealed previously undescribed morphological features of the cell that are important for species recognition. The presence of a single elongated apical vesicle (EAV) ornamented with a row of small knobs, absent in species of the genus Gymnodinium, calls into question the current taxonomic position of the symbiont. The presence of a type E extraplastidial eyespot, the arrangement of the amphiesmal vesicles in series and the absence of trichocysts confirm the affiliation with other symbiotic dinoflagellates and certain genetically related non-symbiotic genera, all belonging to the order Suessiales. The arrangement of the series of vesicles of the analyzed strain is unique within the Suessiales, and the ultrastructure of the pyrenoid is different from other symbiotic dinoflagellates. A large subunit (LSU) rDNA phylogenetic analysis confirmed that the analyzed pelagic symbiont clusters in an independent, well-supported clade within the Suessiales with other sequences of symbiotic dinoflagellates extracted from planktonic foraminifera. Hence a novel genus, Pelagodinium gen. nov., is erected for this pelagic, symbiotic dinoflagellate, and Gymnodinium béii is reclassified as Pelagodinium béii.
基于详细的形态发生分析，重新评估了自由生活阶段的甲藻 Gymnodinium béii 的分类地位，它是有孔虫 Orbulina universa 的共生体。电子显微镜观察揭示了该细胞以前未描述的形态特征，这些特征对于物种识别很重要。单个细长的顶泡（EAV）上有一排小瘤，这在 Gymnodinium 属的物种中不存在，这对共生体的当前分类地位提出了质疑。存在 E 型外质体眼点、 Amphiesmal 泡的串联排列以及没有纤毛囊，这证实了与其他共生甲藻和某些遗传上相关的非共生属的联系，所有这些都属于 Suessiales 目。分析菌株的囊泡系列排列在 Suessiales 中是独特的，而淀粉核的超微结构与其他共生甲藻不同。大亚基（LSU）rDNA 系统发育分析证实，分析的浮游共生体在 Suessiales 内的一个独立的、得到很好支持的分支中聚类，与从浮游有孔虫中提取的其他共生甲藻序列聚类。因此，为这个浮游共生甲藻建立了一个新属，Pelagodinium gen. nov.，并将 Gymnodinium béii 重新分类为 Pelagodinium béii。
