ABSTRACT Ostreopsis mascarenensis is a toxic dinoflagellate described from the Indian Ocean based only on morphology, without molecular data. Morphological features of Ostreopsis have poor taxonomic value, and the addition of genetic data would ensure correct species identification. The present study reinvestigated field samples from Réunion Island and the western Indian Ocean to validate morphological and genetic data of O. mascarenensis from the type locality. A detailed morphological study used light, epifluorescence and scanning electron microscopy, and phylogeny was inferred from sequences of the LSU rDNA (D1–D3 and D8–D10 domains) and ITS–5.8S region obtained from isolated single cells. Morphology mostly agreed with the original description, but we highlight some features that were probably in error in the original description. SEM showed that the epitheca was conspicuously flattened while the hypotheca was convex, which had been previously interpreted as the opposite. Moreover, in contrast with the previous interpretation, the second apical plate was long and narrow, 1.6 to 2 times longer than the apical pore. Phylogenetic analyses showed that O. mascarenensis forms a new lineage among Ostreopsis species, confirming that it is well separated from all other species. Based on these analyses, O. mascarenensis appeared to be related to Ostreopsis fattorussoi and the undescribed species Ostreopsis sp. 3 and sp. 4, but the topologies were not well supported and these relationships remain unclear.

中文翻译：

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来自留尼汪岛（西南印度洋）的 Ostreopsis mascarenensis Quod（Dinophyceae，Gonyaulacales）的再调查：分子系统发育和修正描述

摘要 Ostreopsis mascarenensis 是一种来自印度洋的有毒鞭毛藻，仅基于形态学描述，没有分子数据。Ostreopsis 的形态特征具有较差的分类价值，添加遗传数据将确保正确的物种识别。本研究重新调查了留尼汪岛和西印度洋的野外样本，以验证来自模式所在地的 O. mascarenensis 的形态和遗传数据。使用光、落射荧光和扫描电子显微镜进行了详细的形态学研究，并从 LSU rDNA（D1-D3 和 D8-D10 结构域）和从分离的单细胞中获得的 ITS-5.8S 区域的序列推断系统发育。形态学大体上与原始描述一致，但我们强调了原始描述中可能存在错误的一些特征。SEM 显示上鞘明显变平，而下鞘是凸面，这在以前被解释为相反。而且，与之前的解释相反，第二根尖板又长又窄，比根尖孔长1.6到2倍。系统发育分析表明，O. mascarenensis 在 Ostreopsis 物种中形成了一个新的谱系，证实它与所有其他物种有很好的分离。基于这些分析，O. mascarenensis 似乎与 Ostreopsis fattorussoi 和未描述的物种 Ostreopsis sp. 相关。3 和 sp。4，但拓扑没有得到很好的支持，这些关系仍然不清楚。与之前的解释相反，第二根尖板长而窄，比根尖孔长1.6至2倍。系统发育分析表明，O. mascarenensis 在 Ostreopsis 物种中形成了一个新的谱系，证实它与所有其他物种有很好的分离。基于这些分析，O. mascarenensis 似乎与 Ostreopsis fattorussoi 和未描述的物种 Ostreopsis sp. 相关。3 和 sp。4，但拓扑没有得到很好的支持，这些关系仍然不清楚。与之前的解释相反，第二根尖板长而窄，比根尖孔长1.6至2倍。系统发育分析表明，O. mascarenensis 在 Ostreopsis 物种中形成了一个新的谱系，证实它与所有其他物种有很好的分离。基于这些分析，O. mascarenensis 似乎与 Ostreopsis fattorussoi 和未描述的物种 Ostreopsis sp. 相关。3 和 sp。4，但拓扑没有得到很好的支持，这些关系仍然不清楚。mascarenensis 似乎与 Ostreopsis fattorussoi 和未描述的物种 Ostreopsis sp. 有关。3 和 sp。4，但拓扑没有得到很好的支持，这些关系仍然不清楚。mascarenensis 似乎与 Ostreopsis fattorussoi 和未描述的物种 Ostreopsis sp. 有关。3 和 sp。4，但拓扑没有得到很好的支持，这些关系仍然不清楚。