Data_Sheet_1_Molecular Data Reveal a Cryptic Diversity in the Genus Urotricha (Alveolata, Ciliophora, Prostomatida), a Key Player in Freshwater Lakes, With Remarks on Morphology, Food Preferences, and Distribution.pdf

Species of the ciliate genus Urotricha are key players in freshwater plankton communities. In the pelagial of lakes, about 20 urotrich species occur throughout an annual cycle, some of which play a pivotal role in aquatic food webs. For example, during the phytoplankton spring bloom, they consume a remarkable proportion of the algal production. In ecological studies, urotrich ciliates are usually merely identified to genus rank and grouped into size classes. This is unsatisfying considering the distinct autecological properties of individual species and their specific spatial and temporal distribution patterns. As a basis for future research, we characterized in detail four common urotrich morphotypes, i.e., specimens identified as U. furcata and tentatively as U. agilis, U. pseudofurcata, and U. castalia, using state-of-the-art methods. We used an integrative polyphasic approach, in which morphological studies (in vivo observation, silver staining methods, scanning electron microscopy) were linked with a molecular approach exploiting four different gene fragments as taxonomic DNA barcodes with different resolution potential (SSU rDNA, ITS-1, ITS-2, hypervariable V4 and V9 regions of the SSU rDNA). We shed light on the diversity of urotrich ciliates as well as on their global distribution patterns, and annual cycles. Additionally, we coupled individual species occurrences and environmental parameters, and subsequently modeled the distribution and occurrence, using logistic regressions. Furthermore, for one strain putatively identified as U. castalia, we ascertained the optimal cultivation media and food preferences. Thereby, our comprehensive view on these important freshwater ciliates that frequently occur in environmental high throughput sequencing datasets worldwide will allow future studies to better exploit protistan plankton data from lakes.

纤毛虫属（Urotricha）的物种是淡水浮游生物群落中的关键类群。在湖泊敞水区，全年可检出约20种尾毛虫属物种，其中部分类群在水生食物网中发挥关键作用。例如，在浮游植物春季水华期间，它们可消耗藻类生产量的可观比例。在生态学研究中，尾毛虫属纤毛虫通常仅被鉴定至属级水平，并按体型类群进行归类。考虑到各物种独特的个体生态特性以及其特定的时空分布格局，这种分类方式存在明显局限。为支撑后续研究，我们采用前沿技术手段，对4种常见的尾毛虫属形态型进行了详细表征，即鉴定为叉尾尾毛虫（U. furcata）、暂定为敏捷尾毛虫（U. agilis）、假叉尾尾毛虫（U. pseudofurcata）以及卡斯塔尔尾毛虫（U. castalia）的标本。我们采用整合式多相分类策略：将形态学研究（活体观察、银染法、扫描电子显微镜）与分子生物学方法相结合，利用4个具有不同分辨潜力的基因片段作为分类学DNA条形码（SSU rDNA、ITS-1、ITS-2以及SSU rDNA的高变V4与V9区）。我们阐明了尾毛虫属纤毛虫的物种多样性，以及其全球分布格局与年度发生周期。此外，我们将各物种的出现记录与环境参数进行关联，并随后通过逻辑回归模型对其分布与出现情况进行建模分析。此外，我们针对1株暂定为卡斯塔尔尾毛虫（U. castalia）的菌株，确定了其最适培养基与食物偏好。综上，针对这类在全球环境高通量测序数据集里频繁出现的重要淡水纤毛虫，我们所获得的全面认知将助力后续研究更高效地利用湖泊原生生物浮游生物数据。