School of Earth and Environmental Sciences, College of Natural Sciences, Seoul National University, Seoul, 151-747, Korea.
J Eukaryot Microbiol. 2014 Mar-Apr;61(2):182-203. doi: 10.1111/jeu.12098. Epub 2014 Feb 25.
The marine phototrophic dinoflagellate Gymnodinium smaydae n. sp. is described from cells prepared for light, scanning, and transmission electron microscopy. Also, sequences of the small (SSU) and large subunits (LSU) and the internal transcribed spacer region (ITS1-5.8S-ITS2) of ribosomal DNA were analyzed. This newly isolated dinoflagellate possessed nuclear chambers, nuclear fibrous connective, an apical groove running in a counterclockwise direction around the apex, and a major accessory pigment peridinin, which are four key features for the genus Gymnodinium. The epicone was conical with a round apex, while the hypocone was ellipsoid. Cells growing photosynthetically were 6.3-10.9 μm long and 5.1-10.0 μm wide, and therefore smaller than any other Gymnodinium species so far reported except Gymnodinium nanum. Cells were covered with polygonal amphiesmal vesicles arranged in 11 horizontal rows, and the vesicles were smaller than those of the other Gymnodinium species. This dinoflagellate had a sharp and elongated ventral ridge reaching half way down the hypocone, unlike other Gymnodinium species. Moreover, displacement of the cingulum was 0.4-0.6 × cell length while in other known Gymnodinium species it is less than 0.3 × cell length. In addition, the new species possessed a peduncle, permanent chloroplasts, pyrenoids, trichocysts, pusule systems, and small knobs along the apical furrow, but it lacked an eyespot, nematocysts, and body scales. The sequence of the SSU, ITS1-5.8S-ITS2, and LSU rDNA region differed by 1.5-3.8%, 6.0-17.4%, and 9.1-17.5%, respectively, from those of the most closely related species. The phylogenetic trees demonstrated that the new species belonged to the Gymnodinium clade at the base of a clade consisting of Gymnodinium acidotum, Gymnodinium dorsalisulcum, Gymnodinium eucyaneum, etc. Based on morphological and molecular data, we suggest that the taxon represents a new species, Gymnodinium smaydae n. sp.
海洋光养甲藻 Gymnodinium smaydae n. sp. 是根据为光镜、扫描电镜和透射电镜准备的细胞描述的。此外，核糖体 DNA 的小亚基（SSU）和大亚基（LSU）以及内部转录间隔区（ITS1-5.8S-ITS2）的序列也进行了分析。这种新分离的甲藻具有核室、核纤维连接、沿顶点逆时针方向运行的顶槽以及主要辅助色素 Peridinin，这是 Gymnodinium 属的四个关键特征。上锥顶呈圆锥形，下锥顶呈椭圆形。光合作用的细胞长 6.3-10.9 μm，宽 5.1-10.0 μm，因此比迄今为止报道的任何其他 Gymnodinium 种都小，除了 Gymnodinium nanum。细胞被排列成 11 个水平行的多边形 Amphiesmal 囊泡覆盖，并且这些囊泡比其他 Gymnodinium 种的囊泡小。这种甲藻有一个尖锐而细长的腹脊，延伸到下锥的一半，与其他 Gymnodinium 种不同。此外，中环的位移为 0.4-0.6×细胞长度，而在其他已知的 Gymnodinium 种中，它小于 0.3×细胞长度。此外，新种具有一个柄、永久性叶绿体、淀粉核、刺丝囊、 Pusule 系统和沿顶槽的小突起，但它缺乏眼点、刺细胞和体鳞片。SSU、ITS1-5.8S-ITS2 和 LSU rDNA 区的序列分别与最密切相关的物种相差 1.5-3.8%、6.0-17.4%和 9.1-17.5%。系统发育树表明，新种属于 Gymnodinium 进化枝，位于由 Gymnodinium acidotum、Gymnodinium dorsalisulcum、Gymnodinium eucyaneum 等组成的进化枝的底部。基于形态学和分子数据，我们建议该分类群代表一个新种，即 Gymnodinium smaydae n. sp.
