Studies on diversity and origins of parasitic dinoflagellates.

日本对寄生甲藻的研究很少。本研究的目的是，因此，1）了解日本沿海沃茨周围的寄生甲藻的物种多样性和2）了解他们的起源和他们的系统发育的亲缘关系与其他甲藻的分子系统发育分析的基础上。结果表明，在日本各地共发现寄生甲藻5属8种。这些包括，Blastodinium，Oodinium，Amoebophrya，Syndinium和Duboscquella。我们已经调查了每个物种的帮助下，光和透射电子显微镜。并利用单细胞PCR技术分析了这些种的SSU rDNA序列。分子树分析表明，芽甲藻和卵甲藻起源于典型的甲藻，而变甲藻和合甲藻属于海生藻Ⅱ类群。寄生于纤毛虫类的海洋原生生物Favella ehrenbertina被鉴定为盾盾壳虫Duboscquella aspida。我们发现，这种生物包括在分支命名，海洋泡状组I（MAG-I）。后一个分支被认为是起源于皮可托石大小组分的环境克隆序列的组合，并且没有鉴定出属于该分支的实际生物（尽管最近发现放射虫的寄生虫属于该分支，但它们的形态尚未被研究。Dolven等人，2007年）。因此，我们的发现是这个神秘分支成员的第一个有机体鉴定。MAG-I的环境克隆序列几乎在海洋的任何地方都被检测到，并且MAG-I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.