Early evolution and phylogeny of Phaeophyceae deduced from the cell fine structure, photosynthetic pigments and molecular phylogeny.

星状拟木霉（Giraudyopsis stellifera）的营养细胞具有由粘液物质组成的细胞壁状结构，可育时形成一个或两个菌群。蜂群是梨形的，提供了一个有眼点和异鞭毛侧鞭毛叶绿体;后鞭毛显示绿色荧光。在定居到底层后，蜂群首先发展成匍匐花丝，然后产生直立花丝。叶绿体为典型的有色植物型，具三层的类囊体，包封在带片层中，类核蛋白质包埋在叶绿体中。叶绿素a，c，岩藻黄质，紫黄质和硅藻黄质的存在下，通过HPLC分析显示为主要的光合色素。包括拟Giraudyopsis在内的拟裂殖藻目的系统位置尚不清楚，但利用rbcL基因序列进行的分子系统发育分析表明，拟裂殖藻目与黄藻纲、褐藻纲、裂殖藻纲在系统发育上较为接近 ...更多信息 利用rbcL和18S rDNA序列对中节果盘孢囊藻（Discosporangium mesarthrocarpum）进行分子系统发育分析，结果表明该藻与其他褐藻的姐妹藻--柔嫩红藻（Choristocarpus tenellus）形成单系分支。虽然中节果藻具有独特的盘状多室生殖器官，但中节果藻和纤细藻具有以下被认为是褐藻中的近形特征的基本形态特征：1）顶端（和扩散）生长; 2）单列，近二歧分枝的细丝; 3）每个细胞多个叶绿体，无核蛋白质; 4）缺乏异丝和褐藻毛。澳大利亚D. mesarthrocarpum标本的rbcL DNA序列显示出相当大的偏差，从地中海和Macaronesian标本。因此，建议在该属中存在第二个种，然而，本报告暂停了对该推定种的分类处理。鉴于中节果盾叶薯蓣的系统地位较高，建议重新评价盘囊藻科和盘囊藻目。少

Vegetative cells of Giraudyopsis stellifera (Chrysomeridales) have cell wall-like structures composed of mucilaginous substances, and form one or two swarmer(s) when fertile. The swarmers are pear-shaped, provided with a chloroplast having an eyespot and heterokont lateral flagella ; the posterior flagellum shows green fluorescence. After settlement to the substratum, the swarmer first develops into prostrate filaments which then produce erect filaments. The chloroplasts are of typical chromophyte-type having triple-layered thylakoids enclosed in a girdle lamella, and a pyrenoid embedded in the chloroplast. Presence of chlorophylls a,c, fucoxanthin, violaxanthin and diatoxanthin were shown as major photosynthetic pigments by HPLC analyses. Systematic position of Chrysomeridales including Giraudyopsis in higher rank is unclear, but the molecular phylogenetic analyses using rbcL gene sequences revealed that the species is phylogenetically close to Xanthophyceae, Phaeophyceae, Schizocladi … More ophyceae and Phaeothamniophyceae, but was not included in them, and formed clade with Tetrasporopsis (incertae cedis).A molecular phylogenetic analysis of the brown alga Discosporangium mesarthrocarpum using rbcL and 18S rDNA sequences revealed that the species forms a monophyletic clade with Choristocarpus tenellus that is sister to all other brown algae. Although D.mesarthrocarpum has unique disc-shaped plurilocular reproductive organs, D.mesarthrocarpum and C.tenellus share the following basic morphological features which are considered to be plesiomorphic characters in the brown algae : 1) Apical (and diffuse) growth ; 2) Uniseriate, subdichotomously branched filaments ; 3) Multiple chloroplasts per cell without pyrenoids ; 4) Lack of heterotrichy and phaeophycean hairs. The rbcL DNA sequence of an Australian D.mesarthrocarpum specimen showed considerable deviation from Mediterranean and Macaronesian specimens. Therefore, the presence of a second species in the genus is suggested, however, the taxonomic treatment of this putative species is suspended in the present report. Regarding the higher rank systematic position of D.mesarthrocarpum, reappraisal of Discosporangiaceae and Discosporangiales is proposed. Less