Yamada Norico, Sakai Hiroto, Onuma Ryo, Kroth Peter G, Horiguchi Takeo
Department of Natural History Sciences, Graduate School of Science, Hokkaido University, Sapporo, Japan.
Department of Biology, University of Konstanz, Konstanz, Germany.
Front Plant Sci. 2020 Nov 19;11:591050. doi: 10.3389/fpls.2020.591050. eCollection 2020.
and are benthic dinoflagellates possessing diatom-derived tertiary plastids, so-called dinotoms. Due to the lack of available genetic information, their phylogenetic relationship remains unknown. In this study, sequencing of 18S ribosomal DNA (rDNA) and the L gene from temporary cultures isolated from natural samples revealed that they are close relatives of another dinotom, . The morphologies of these three dinotoms differ significantly from each other; however, they share a distinctive life cycle, in which the non-motile cells without flagella are their dominant phase. Cell division occurs in this non-motile phase, while swimming cells only appear for several hours after being released from each daughter cell. Furthermore, we succeeded in isolating and establishing two novel dinotom strains, HG180 and HG204, which show a similar life cycle and are phylogenetically closely related to the aforementioned three species. The non-motile cells of strain HG180 are characterized by the possession of a hemispheroidal cell covered with numerous nodes, while those of the strain HG204 form aggregations consisting of spherical smooth-surface cells. Based on the similarity in life cycles and phylogenetic closeness, we conclude that all five species should belong to a single genus, , the oldest genus within this clade. We transferred and to , and described strains HG180 and HG204 as sp. nov. and sp. nov.
[具体物种名称1]和[具体物种名称2]是具有硅藻衍生的三级质体的底栖甲藻，即所谓的甲藻硅藻。由于缺乏可用的遗传信息，它们的系统发育关系仍然未知。在本研究中，对从自然样本中分离的临时培养物的18S核糖体DNA（rDNA）和L基因进行测序，结果表明它们是另一种甲藻硅藻[具体物种名称3]的近亲。这三种甲藻硅藻的形态彼此有显著差异；然而，它们共享一个独特的生命周期，其中无鞭毛的非游动细胞是其主要阶段。细胞分裂发生在这个非游动阶段，而游动细胞仅在从每个子细胞释放后出现几个小时。此外，我们成功分离并建立了两个新的甲藻硅藻菌株，HG180和HG204，它们表现出相似的生命周期，并且在系统发育上与上述三个物种密切相关。HG180菌株的非游动细胞的特征是拥有一个覆盖着许多结节的半球形细胞，而HG204菌株的非游动细胞形成由球形光滑表面细胞组成的聚集体。基于生命周期的相似性和系统发育的亲缘关系，我们得出结论，所有这五个物种都应属于一个单一的属[具体属名]，这是该进化枝中最古老的属。我们将[具体物种名称1]和[具体物种名称2]转移到[具体属名]，并将HG180菌株和HG204菌株分别描述为[具体物种名称4]新种和[具体物种名称5]新种。
