Studies on diversity and origins of parasitic dinoflagellates.

日本对寄生鞭毛藻的研究很少。因此，本研究的目的是：1)了解日本沿海地区寄生鞭毛藻的物种多样性；2)基于分子系统发育分析，了解其起源及其与其他鞭毛藻的系统发育亲缘关系。本研究共鉴定出日本不同地区寄生鞭毛虫5属8种。这些包括囊胚，卵胚，变形虫，Syndinium和Duboscquella。我们用光学显微镜和透射电子显微镜研究了每个物种。我们还利用单细胞PCR技术分析了这些物种的SSU rDNA序列。我们的分子树表明Blastodinium和Oodinium起源于典型的鞭毛类，而amoeophrya和Syndiniuim属于海洋肺泡门II群。寄生丁氏纤毛虫的海洋原生生物被鉴定为杜氏纤毛虫（Duboscquella aspida）。我们发现这种生物被包括在被命名为海洋肺泡群I （MAG-I）的分支中。后一支系被认为是由源自微浮游生物大小的片段的环境克隆序列组合而成的，并没有确定属于该支系的实际生物（尽管放射虫的寄生虫最近被发现属于该支系，但其形态尚未被研究）。Dolven et al. 2007)。因此，我们的发现是对这一神秘分支成员的首次有机体鉴定。几乎在海洋的任何地方都检测到mag - 1的环境克隆序列，并且mag - 1的成员主要由放射虫或纤毛虫的寄生虫组成，这表明海洋环境中充满了这些寄生虫的（运动细胞）。我们的研究表明寄生在海洋生态中的重要性。

Little studies on parasitic dinoflagellates have been undertaken in Japan. The aims of this research are, therefore, 1)to understand species diversity of parasitic dinoflagellates around the Japanese coastal waters and 2)to understand their origins and their phylogenetic affinities with other dinoflagellates based on molecular phylogenetic analyses. In summary, we were able to recognize 8 species of parasitic dinoflagellates from various localities of Japan, belonging to 5 genera. These include, Blastodinium, Oodinium, Amoebophrya, Syndinium and Duboscquella. We have investigated each species with the aid of light and transmission electron microscopes. Also we have analyzed SSU rDNA sequences of these species using single cell PCR technique. Our molecular trees suggested that Blastodinium and Oodinium had originated from typical dinoflagellates, while Amoebophrya and Syndiniuim belong to the clade named Marine Alveoalte Group II. The marine protist parasitizing tintinnid ciliate, Favella ehrenbergii was identified as Duboscquella aspida. We found that this organism was included in the clade named, Marine Alveolate Group I (MAG-I). The latter clade has been recognized as assemblage of only environmental clone sequences originated from picoplanktonic size fractions and no actual organisms belonging to this clade have been identified (Although parasites of radiolarians have been found to belong this clade recently, their morphology has not been investigated. Dolven et al. 2007). Our finding, therefore, is the first organismal identification of the member of this enigmatic clade. The facts that environmental clone sequences of MAG-I have been detected almost anywhere in the ocean and members of the MAG-I mainly consists of parasites of radiolarians or ciliates suggest that the oceanic environments are full of (motile cells of) these parasites. Our research suggested importance of parasitism in the marine ocean ecology.