Climacodium frauenfeldianum is a planktonic chain-forming diatom able to proliferate in severely oligotrophic waters of tropical seas. In this study, a strain of C. frauenfeldianum, the type of Climacodium, was established in culture from the tropical southwestern Atlantic Ocean off Brazil. SEM observations showed weakly silicified cells, without visible surface sculpturing. In the small subunit (SSU) rRNA and ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit (rbcL) gene phylogeny, C. frauenfeldianum clustered with sequences of Bellerochea malleus (the type of Bellerochea) and B. horologicalis. Contrary to previous classifications that placed Climacodium in the Hemiaulaceae, Climacodium and Bellerochea should be placed in the same family, Bellerocheaceae. The species Bellerochea yucatanensis needs further research because sequences of the single strain available clustered with the genus Lithodesmioides. In adaptation to the oligotrophic open ocean environment, C. frauenfeldianum seems to have evolved an appearance closer to Hemiaulus, i.e. very lightly silicified flat cells with long elevations, and with diazotrophic cyanobionts.

中文翻译：

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分子系统发育表明浮游硅藻 Climacodium 和 Bellerochea (Lithodesmiales, Mediophyceae) 的亲和力

Climacodium frauenfeldianum 是一种浮游链形成硅藻，能够在热带海域的严重贫营养水域中增殖。在这项研究中，一种 C. frauenfeldianum 菌株（一种 C. frauenfeldianum）是在巴西附近热带西南大西洋的培养物中建立的。SEM 观察显示弱硅化细胞，没有可见的表面雕刻。在小亚基 (SSU) rRNA 和核酮糖-1,5-二磷酸羧化酶/加氧酶大亚基 (rbcL) 基因系统发育中，C. frauenfeldianum 与 Bellerochea malleus（Bellerochea 的类型）和 B. horologicalis 的序列聚集在一起。与之前将 Climacodium 归入半叶草科的分类相反，Climacodium 和 Bellerochea 应归入相同的 Bellerocheaceae 科。Bellerochea yucatanensis 物种需要进一步研究，因为可用的单个菌株的序列与 Lithodesmioides 属聚集在一起。为了适应贫营养的开阔海洋环境，C. frauenfeldianum 似乎已经进化出更接近于 Hemiulus 的外观，即具有长海拔的非常轻微的硅化扁平细胞和固氮蓝藻。