亚气生球状绿藻一新种——重庆单星藻

单星藻隶属于绿藻纲环藻目栅藻科, 多为单细胞或聚合群体, 属内已知种类多发现于气生、亚气生生境, 在天然抗氧化剂和食品色素生产等领域具有广阔应用前景。但目前关于该类群的基础分类学研究相对薄弱, 阻碍了这些优质藻种资源的进一步开发利用。本研究从重庆市及周口市采集到2株单星藻, 经形态学及18S rDNA、ITS和tufA三个分子标记鉴定为单星藻属一新种, 命名为重庆单星藻Coelastrella chongqingensis sp. nov.。重庆单星藻显著的形态特征是细胞壁近似光滑或仅具细微皱纹, 不具有典型单星藻类群纵向分布的肋纹, 幼期细胞多呈椭球形或卵形, 末端钝圆, 细胞大小约(6—9) μm×(5—7) μm。成熟细胞多呈圆球形或椭球形, 直径约8—14—(18) μm。系统发育分析结果显示重庆单星藻与另外2种细胞壁近似光滑的藻株液泡单星藻Coelastrella vacuolata和薄壁单星藻Coelastrella tenuitheca具有最近的亲缘关系, 三者在基于tufA序列的系统发育分析中形成独立单系分支, 代表单星藻属第三种形态型, 即细胞壁近似光滑或仅具细微网纹, 无单星藻属典型的纵向肋纹。新种的发现扩充了单星藻属第三种形态型的物种组成, 为该属进一步的分类学修订打下基础。

COELASTRELLA CHONGQINGENSIS SP. NOV., A NOVEL SPECIES OF THE SUBAERIAL COCCOID GREEN ALGAE WITHIN THE COELASTRELLA (SCENEDESMACEAE,SPHAEROPLEALES)

The genus Coelastrella was taxonomically positioned in the family Scenedesmaceae (Sphaeropleales, Chlorophyceae), and was characterized as unicellular or few-celled aggregations. Species within the genus are mostly found in aerial and sub-aerial habitats, which are different from other freshwater-living members of Scenedesmaceae. They have good tolerance to some stress conditions, such as high temperature, high salt, and ultraviolet. The most notable feature of the genus Coelastrella is that the cells tend to accumulate carotenoids and oils in the late growth stage, or under some stress conditions such as nitrogen deficiency and high salt. This group has been proved to have broad application prospects in the fields of natural antioxidants and food pigment production. In this study, two strains of the genus Coelastrella were collected from Chongqing and Xinyang, and they were identified as a new species of the genus Coelastrella by morphology and three molecular markers of 18S rDNA, ITS, and tufA gene. The remarkable morphological feature of Coelastrella chongqingensis is that the cell wall is approximately smooth or only slightly wrinkled, without the meridianal ribs of the typical Coelastrella species. The young cells are mostly ellipsoidal or oval with obtuse ends with a size of (0—9) μm×(5—7) μm. The mature cells are mostly spherical or ellipsoidal with a size of 8—14—(18) μm. The results of the phylogenetic analysis showed that Coelastrella chongqingensis was closely related to Coelastrella vacuolata and Coelastrella tenuitheca. They all have similar morphotype, and formed independent monophyletic group in the phylogeny of tufA gene. This branch represents the third morphotype of Coelastrella, that is, the cell wall is approximately smooth or with a network of fine ribs without the typical meridional ribs of Coelastrella.