Remias Daniel, Procházková Lenka, Holzinger Andreas, Nedbalová Linda
University of Applied Sciences, Campus Wels, Stelzhamerstr. 23, A-4600 Wels, Austria.
Charles University, Faculty of Science, Department of Ecology, Viničná7, CZ-128 44 Prague, Czech Republic.
Phycologia. 2018;57(5):581-592. doi: 10.2216/18-45.1.
Long-lasting, slowly melting snowfields in mountainous regions are frequently populated by specialised microalgae whose diversity is still vastly underestimated. Cysts causing sub-surficial green snow were collected in the Austrian Alps, Tyrol, and morphologically accorded to the snow alga Chodat, initially described from Switzerland. The cytology and photobiology of this population were investigated to understand mechanisms of adaptation to the harsh habitat. Cysts of K-1 had secondary cell walls with pronounced rib-like surface structures and contained several small spherical plastids. The cytoplasm was dominated by lipid bodies, which developed reddish secondary pigmentation. Partial life cycle observations showed that daughter cells lacked structured cell walls. Cysts performed active photosynthesis at temperature conditions close to the freezing point and were photoinhibited at irradiances greater than 70 μmol m s. This corresponded exactly to habitat conditions 20 to 40 cm below the snow surface. Phylogenetic analyses using 18S rDNA, L and ITS2 rDNA sequences indicated that K-1 is related to , known to contain several snow algae. The taxon forms an independent lineage and is clearly genetically distinct from the type strain of var. from North America that is supposed to have morphologically identical cysts. For a taxonomic treatment including a species assignment of K-1 from Europe within , flagellates will have to be cultivated from cysts or from acquired field material for a detailed morphological description. Acquisition and genetic analysis of cysts that resemble from America could elucidate their relationship to European samples.
山区持久且缓慢融化的雪原中常常生长着一些特殊的微藻，其多样性仍被大大低估。在奥地利蒂罗尔州的阿尔卑斯山收集到了导致地表下绿色积雪的藻孢囊，其形态与最初在瑞士描述的雪藻Chodat相符。对该种群的细胞学和光生物学进行了研究，以了解其适应恶劣生境的机制。K-1藻孢囊具有带有明显肋状表面结构的次生细胞壁，并且含有几个小的球形质体。细胞质中主要是脂质体，其呈现出微红的次生色素沉着。部分生命周期观察表明，子细胞缺乏结构化的细胞壁。藻孢囊在接近冰点的温度条件下进行活跃的光合作用，并且在辐照度大于70 μmol m² s⁻¹时受到光抑制。这与雪面以下20至40厘米处的生境条件完全相符。使用18S rDNA、L和ITS2 rDNA序列进行的系统发育分析表明，K-1与已知包含几种雪藻的属相关。该分类单元形成一个独立的谱系，并且在遗传上明显不同于来自北美的var. 类型菌株，后者被认为具有形态相同的藻孢囊。为了进行分类处理，包括对来自欧洲的K-1在属内进行物种鉴定，必须从藻孢囊或获取的野外材料中培养鞭毛虫，以便进行详细的形态描述。获取并对类似于来自美洲的藻孢囊进行遗传分析，可以阐明它们与欧洲样本的关系。
