A hole in the nematosphere: tardigrades and rotifers dominate the cryoconite hole environment, whereas nematodes are missing
A hole in the nematosphere: tardigrades and rotifers dominate the cryoconite hole environment, whereas nematodes are missing
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DOI：
10.1111/jzo.12832
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发表时间：
2020-09
影响因子：
2
通讯作者：
K. Zawierucha;D. Porazinska;G. Ficetola;R. Ambrosini;G. Baccolo;Jakub Buda;J. Ceballos;Miloslav Devetter;R. Dial;A. Franzetti;U. Fuglewicz;L. Gielly;E. Łokas;K. Janko;T. Jaroměřská;A. Koscinski;A. Kozłowska;M. Ono;I. Parnikoza;F. Pittino;E. Poniecka;P. Sommers;S. K. Schmidt;D. Shain;S. Sikorska;J. Uetake;N. Takeuchi
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文献类型：
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作者：
K. Zawierucha;D. Porazinska;G. Ficetola;R. Ambrosini;G. Baccolo;Jakub Buda;J. Ceballos;Miloslav Devetter;R. Dial;A. Franzetti;U. Fuglewicz;L. Gielly;E. Łokas;K. Janko;T. Jaroměřská;A. Koscinski;A. Kozłowska;M. Ono;I. Parnikoza;F. Pittino;E. Poniecka;P. Sommers;S. K. Schmidt;D. Shain;S. Sikorska;J. Uetake;N. Takeuchi
微型无脊椎动物在冰川上的全球分布情况鲜为人知，冰川是最冷的生物群。由于对恶劣条件的耐受性、体积小和扩散能力，线虫、迟滞和轮虫被认为是世界性的，共同生活在不同的生态系统中。在这项研究中，我们调查了它们在冰锥洞穴中的全球分布-一种直接在冰川冰中形成的淡水水库，在冰川上创造了生物多样性的热点。我们分析了来自世界各地(北极、北冰洋、斯堪的纳维亚、阿尔卑斯山、高加索、西伯利亚、中亚、非洲、南美洲和南极洲)42个冰川的冰锥样本(使用经典的显微镜观察和环境DNA元数据库编码)，以及使用文献数据。来自南极、喀喇昆仑和阿尔卑斯山的样品使用下一代测序(NGS)和显微镜下的经典观察进行了分析，而所有其他样品只进行了显微镜分析。研究发现了三种一般结果：(1)延缓动物和轮虫是低温融合孔中最常见的无脊椎动物；(2)延缓动物和轮虫经常共存，其中一种或另一种占优势，但优势分类群因地区或冰川而异；(3)地球上一直没有线虫--地球上最丰富、超多样性和分布最广的后生动物，包括在冰川表面周围和播种的环境中--一直没有出现线虫。尽管冰孔中的环境条件大致相似，但不同冰川的迟缓虫和轮虫的分布是不同的，但不是以任何可预测的方式，这表明它们的分布主要取决于冰上带的随机扩散、极端变化或竞争。尽管在冰上栖息地发现了线虫，但冰锥洞穴环境似乎不能为线虫的生长和繁殖提供必要的条件。缺乏对长期低温(~0℃)的生理适应，以及在低温球洞环境中对不同食物来源的竞争，可能解释了在低温球洞中没有线虫的原因。
The worldwide distribution of microinvertebrates on glaciers, the coldest biome, is poorly known. Owing to their tolerance to hostile conditions, small size and dispersal abilities, nematodes, tardigrades and rotifers are considered cosmopolitan and together inhabit various ecosystems. In this study, we investigated their global distribution in cryoconite holes – a type of freshwater reservoir forming directly in the glacial ice that creates biodiversity hotspots on glaciers. We analysed cryoconite samples (using classical microscopic observations and environmental DNA metabarcoding) from 42 glaciers located around the world (the Arctic, Subarctic, Scandinavia, the Alps, the Caucasus, Siberia, Central Asia, Africa, South America and Antarctica), as well as using literature data. Samples from Antarctic, Karakoram and the Alps were analysed using next‐generation sequencing (NGS) and classical observations under microscopes, while all other samples were analysed by microscope alone. Three general outcomes were found: (1) tardigrades and rotifers represented the most common invertebrates in cryoconite holes; (2) tardigrades and rotifers often coexisted together, with one or the other dominating, but the dominant taxon varied by region or by glacier; (3) nematodes – the most abundant, hyperdiverse and widespread metazoans on Earth, including in environments surrounding and seeding glacial surfaces – were consistently absent from cryoconite holes. Despite the general similarity of environmental conditions in cryoconite holes, the distribution of tardigrades and rotifers differed among glaciers, but not in any predictable way, suggesting that their distribution mostly depended on the random dispersal, extreme changes of supraglacial zone or competition. Although nematodes have been found in supraglacial habitats, cryoconite hole environments seem not to provide the necessary conditions for their growth and reproduction. Lack of physiological adaptations to permanently low temperatures (~0°C) and competition for different food resources in the cryoconite hole environment may explain the absence of nematodes in cryoconite holes.