有壳虫(Testacea)是一类常见的自由生活的原生动物, 在生态系统物质循环和能量流动中发挥重要作用。作者在分析地球三极(北极、南极、西藏)地区有壳虫种类名录(62属315种)基础上, 对有壳虫区系特征、地理分布及其影响因素进行了研究。结果显示, 北极地区已记录25科51属232种; 南极地区20科30属131种; 西藏地区22科42属173种。三个地区物种丰富度最高的属均为砂壳虫属(Difflugia)、匣壳虫属(Centropyxis)、梨壳虫属(Nebela)、鳞壳虫属(Euglypha)和表壳虫属(Arcella); 5个属的种数分别占北极、南极、西藏总种数的51.3%、63.4%和60.1%。此外, 3个地区共有种数是73(23.2%), 共有属数是24(38.7%); 仅在1个地区记录的种数是167种(53.0%)。在三极地区40个亚区域, 苔藓鳞盖虫(Assulina muscorum)和旋匣壳虫(Centropyxis aerophila)的分布最广泛, 出现频率均高达90%。聚类分析显示, 三个地区种水平相似性系数为51.3-56.3%, 属于中等相似, 北极和西藏相似系数最大。相似性分析表明, 虽然有壳虫具有较强的长距离被动扩散能力, 但是一些大于100 μm的种类不是全球性分布。有壳虫的地理分布格局与个体大小、生境类型、地质历史事件等密切相关, 分析结果受物种鉴定标准、样品数量、空间尺度大小等因素影响。

Testacea (or testate amoebae, thecamoebians) are free-living amoeboid protozoa inhabiting a shell or test and they play an important role in material cycle and energy flow in terrestrial and aquatic ecosystems. The fauna of Testacea was analyzed from three polar regions of the Earth (Arctic, Antarctic and Tibet). In total, 315 species from 62 genera were recorded in the polar regions, i.e. 232 species (51 genera) in the Arctic, 131 species (30 genera) in the Antarctic, and 173 species (42 genera) in Tibet. In each polar region, the most diverse genera were Arcella, Centropyxis,Difflugia, Euglypha, Nebela; they accounted for 51.3%, 63.4% and 60.1% of the total species number in the Arctic, Antarctic and Tibet, respectively. Seventy-three species (23.2% of all species) and twenty-four genera (38.7% of all genera) were common to the three polar regions. One hundred and sixty-seven species (53.0% of species) were found only in one of the polar regions. Both Assulina muscorum and Centropyxis aerophila were widely distributed with the highest frequency (90%) in 40 subregions from the Arctic, Antarctic and Tibet. Cluster analysis revealed that the highest species-level similarity of Testacea was between the Arctic and Tibet (56.3%). Further, species similarity was the highest between the Arctic and Tibet based on Arcellinida species data, but the lowest based on filose Testacea species. Distinct differences in Testacea fauna indicate that some species are not ubiquitously distributed in spite of better passive long-distance dispersal than macro-organisms. Geographic distributional patterns of Testacea diversity are closely related to body size, habitat type and historical events, and our perception of these patterns are strongly influenced by taxonomic resolution (morphological criteria), sampling effort and spatial scales. We propose that study of genetic diversity among and within common Testacea morphospecies in relation to ecological and historical factors will elucidate geographic distributional patterns within this interesting group.