A crucial step in understanding glacial ecosystems is to elucidate their biodiversity. Although tardigrades (water bears) are one of the most common and abundant metazoans inhabiting glaciers, knowledge of their taxonomic diversity on these ice masses remains scarce. The fragmentary data about the diversity of metazoans in glacial ecosystems is a warning sign in the era of global warming that seriously threatens cold-adapted specialists. Based on morphological, morphometric and DNA analyses (18S rRNA, 28S rRNA, COI), we identified tardigrade taxa from water-filled reservoirs in the glacier surface (cryoconite holes) in the Arctic (Svalbard and Greenland). Here we describe three species new to science: Pilatobius glacialis sp. nov., Acutuncus mariae sp. nov. and Grevenius cryophilus sp. nov. In addition to their morphological and genetic differences, these species are easily distinguished from their close relatives by their thermally stable niche, cryoconite holes, in which water temperature at the bottom oscillates around 0.1 °C during the polar summer. Moreover, we found the genus Acutuncus, considered a pan-Antarctic taxon, in cryoconite holes on Svalbard. Additionally, we discovered three new species of the Hypsibius dujardini complex by DNA analysis. Their delimitation is currently based on genetic differences and further morphometric studies may aid in distinguishing them. Our study revealed a new view on the biogeography of glacier tardigrades and the genus Acutuncus, as well as emphasized the uniqueness of glacier metazoans. Tardigrade species inhabiting cryoconite holes may be either morphologically the same (P. glacialis sp. nov.), or very similar to species inhabiting other ecosystems (H. dujardini complex), but they differ in DNA. On other hands, others are unique in both morphology and DNA (G. cryophilus sp. nov.) indicating that the properties of specific habitats shape speciation and, as in cryoconite holes, the reason might be their thermal regime. Therefore, we suggest using the ecological background as well as habitat characteristics in taxonomic descriptions and the differential diagnosis of new tardigrade species.

了解冰川生态系统的关键步骤是阐明其生物多样性。尽管缓步动物（水熊）是居住在冰川上的最常见和最丰富的后生动物之一，但对它们在这些冰块上的分类学多样性的了解仍然很少。关于冰川生态系统中后生动物多样性的零碎数据是全球变暖时代的一个警告信号，严重威胁着适应寒冷的专家。基于形态学，形态计量学和DNA分析（18S rRNA，28S rRNA，COI），我们从北极（斯瓦尔巴特群岛和格陵兰岛）冰川表面（冰砾岩孔）中充满水的储层中鉴定了缓降类群。在这里，我们描述了三种新的科学物种：Pilatobius glacialis sp。十一月，Acutuncus mariae sp。十一月 和Grevenius cryophilus sp。十一月 除了它们的形态和遗传差异外，这些物种还因其热稳定的利基，冰孔洞而容易地与近缘种区别开来，在极地夏季，底部的水温在0.1°C左右波动。此外，我们在斯瓦尔巴特群岛的冰冻孔中发现了Acutuncus属，被认为是泛南极的分类群。此外，我们通过DNA分析发现了三种新的Hypsibius dujardini复合体。目前，它们的划分基于遗传差异，进一步的形态计量学研究可能有助于区分它们。我们的研究揭示了关于冰川缓流生物和刺cut属生物地理的新观点，并强调冰川后生动物的独特性。居住在冰冻洞中的Tardigrade物种在形态上可能相同（P. glacialis sp。nov。），或者与居住在其他生态系统中的物种（H. dujardini complex）非常相似，但是它们的DNA不同。另一方面，其他在形态和DNA方面都是独特的（G. cryophilus sp。nov。），这表明特定生境的特性会影响物种形成，就像在冰孔洞中一样，原因可能是其热态。因此，我们建议在分类学描述和新的缓行物种的鉴别诊断中使用生态背景和生境特征。