Abstract: 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 Scotiella cryophila sensu 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 S. cryophila 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−2 s−1. This corresponded exactly to habitat conditions 20 to 40 cm below the snow surface. Phylogenetic analyses using 18S rDNA, rbcL and ITS2 rDNA sequences indicated that S. cryophila K-1 is related to Chloromonas, known to contain several snow algae. The taxon forms an independent lineage and is clearly genetically distinct from the type strain of Chloromonas rosae var. psychrophila from North America that is supposed to have morphologically identical cysts. For a taxonomic treatment including a species assignment of S. cryophila K-1 from Europe within Chloromonas, 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 S. cryophila from America could elucidate their relationship to European samples.

中文翻译：

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来自奥地利阿尔卑斯山的雪藻 Scotiella cryophila K-1 (Chlamydomonadales, Chlorophyta) 的生态学、细胞学和系统发育

摘要：山区长期存在、缓慢融化的雪原经常居住着特殊的微藻，其多样性仍然被大大低估。在奥地利阿尔卑斯山蒂罗尔收集了导致地下绿雪的囊肿，并且在形态上符合最初描述自瑞士的雪藻 Scotiella cryophila sensu Chodat。对该种群的细胞学和光生物学进行了调查，以了解适应恶劣栖息地的机制。S. cryophila K-1 的囊肿具有次生细胞壁，具有明显的肋状表面结构，并含有几个小的球形质体。细胞质以脂质体为主，形成微红色的继发性色素沉着。部分生命周期观察表明子细胞缺乏结构化的细胞壁。囊肿在接近冰点的温度条件下进行活跃的光合作用，并且在大于 70 μmol m-2 s-1 的辐照度下受到光抑制。这恰好对应于雪面以下 20 至 40 厘米的栖息地条件。使用 18S rDNA、rbcL 和 ITS2 rDNA 序列的系统发育分析表明，嗜冷链球菌 K-1 与已知含有几种雪藻的绿单胞菌有关。该分类单元形成了一个独立的谱系，并且在遗传上明显不同于 Chloromonas rosae var 的类型菌株。来自北美的嗜冷菌，应该具有形态相同的囊肿。对于分类学处理，包括在氯单胞菌内对来自欧洲的 S. cryophila K-1 进行物种分配，必须从囊肿或从获得的田间材料中培养鞭毛虫，以进行详细的形态描述。