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A hole in the nematosphere: tardigrades and rotifers dominate the cryoconite hole environment, whereas nematodes are missing
Journal of Zoology ( IF 2 ) Pub Date : 2020-09-19 , DOI: 10.1111/jzo.12832
K. Zawierucha 1 , D. L. Porazinska 2 , G. F. Ficetola 3, 4 , R. Ambrosini 3 , G. Baccolo 5 , J. Buda 1 , J. L. Ceballos 6 , M. Devetter 7, 8 , R. Dial 9 , A. Franzetti 5 , U. Fuglewicz 10 , L. Gielly 4 , E. Łokas 11 , K. Janko 12, 13 , T. Novotna Jaromerska 14 , A. Kościński 10 , A. Kozłowska 1 , M. Ono 15 , I. Parnikoza 16, 17 , F. Pittino 5 , E. Poniecka 18 , P. Sommers 19 , S. K. Schmidt 19 , D. Shain 20 , S. Sikorska 1 , J. Uetake 21 , N. Takeuchi 22
Affiliation  

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.

中文翻译:

线虫圈中的一个洞:在低温暗孔环境中,节肢动物和轮虫占主导地位,而线虫则缺失

冰川是最冷的生物群落,在冰川上的微无脊椎动物在世界范围内的分布却鲜为人知。由于其对敌对条件的耐受性,小尺寸和分散能力,因此线虫,缓坡和轮虫被认为是世界性的,并共同栖息于各种生态系统中。在这项研究中,我们调查了它们在冰冻洞中的全球分布-一种直接在冰川冰中形成的淡水储层,在冰川上形成生物多样性热点。我们还分析了来自世界各地42个冰川(北极,亚北极,斯堪的纳维亚半岛,阿尔卑斯山,高加索,西伯利亚,中亚,非洲,南美和南极洲)的冰冻岩样品(使用经典的显微镜观察和环境DNA元条形码)如使用文献数据。来自南极的样本 使用下一代测序(NGS)和传统观察在显微镜下分析喀喇昆仑山和阿尔卑斯山,而其他所有样品则仅通过显微镜进行分析。发现了三个总体结果:(1)缓坡和轮虫是冰冻洞中最常见的无脊椎动物;(2)节肢动物和轮虫经常并存,彼此占主导,但主要的分类群因地区或冰川而异;(3)线虫-地球上最丰富,种类最多,分布最广泛的后生动物,包括在冰面周围和种子表面上的环境中-始终没有冰孔洞。尽管冰冻洞中的环境条件普遍相似,但冰川之间的缓坡和轮虫的分布有所不同,但没有任何可预测的方式,这表明它们的分布主要取决于随机分散,沿冰川带或竞争的极端变化。尽管在冰川生境中发现了线虫,但低温圆锥孔环境似乎并未为其生长和繁殖提供必要条件。在低温孔洞环境中缺乏对永久低温(〜0°C)的生理适应性以及对不同食物资源的竞争可能解释了低温孔洞中没有线虫。
更新日期:2020-09-19
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