Phylogenetic and morphological differences of Arctic and Antarctic choanoflagellates

异养纳米鞭毛虫在南极和北极海洋生态系统中扮演着非常重要的角色。在这些原生生物中，有尾鞭毛虫是南极和北极海洋纳米浮游生物中一个显著而丰富的组成部分。虽然已经发表了一些关于有尾鞭毛虫的定量和定性研究，但最近对海洋纳米动物的分子生物学研究表明，对这些微小生物(细胞大小为3-6微米)的形态调查揭示的分类分辨率有限。然而，到目前为止，只有大约三种海洋尾鞭毛虫被测序(18S RDNA)。在拟议的项目期间，将获取纳米原生生物的培养物，结合形态和分子生物学方法对其进行分析，并获得关于这些高度可变的原生生物分布的信息。我们想回答以下问题：在北极和南极水域中发现的有尾鞭毛虫的分子身份是什么？南极是否存在具有相同18S rDNA图谱的南极尾鞭毛虫物种，表明它们是全球分布的？18S rDNA基因的变异性有多大，部分序列能否被用来开发一种可靠的海洋脊椎动物定量和定性分析方法？进一步研究后生鞭毛虫1)作为后生动物的姊妹群，从系统发育的角度来看将是非常有意义的，2)作为远洋食物网基础上的一个生产力很高的群，对于更广泛地了解极地地区的生态过程将特别有意义。

Heterotrophic nanoflagellates play a very important role in marine Antarctic and Arctic ecosystems. Among these protists, choanoflagellates form a conspicuous and abundant component of the Antarctic and arctic marine nanoplankton. Although a number of quantitative and qualitative studies have been published on choanoflagellates, recent molecular biological studies of marine nanofauna indicated that morphological investigations of these tiny organisms (3-6µm cell size) reveal only limited taxonomic resolution. However, until now only about three marine choanoflagellate species have been sequenced (18S rDNA). During the proposed project will acquire cultures of nanoprotists, analyse them combining morphological and molecular biological methods and to receive information on the distribution of these highly variable protists. We would like to address the following questions: What is the molecular identity of choanoflagellates found in Artic and Antarctic waters? Do there exist Antarctic choanoflagellate species with the same 18S rDNA pattern indicating a global distribution? How variable is the 18S rDNA gene and can parts of the sequence be used to develop a method for reliable quantitative and qualitative analyses of marine choanoflagellates? Further research on choanoflagellates 1) as a sister group of metazoans would be very interesting from the viewpoint of phylogeny and 2) as a very productive group at the basis of the pelagic food web would be of special interest for a broader understanding of ecological processes in polar regions.