Biocenter Cologne, Zoological Institute, Department of General Ecology, University of Cologne, Germany.
Eur J Protistol. 2012 Nov;48(4):263-73. doi: 10.1016/j.ejop.2012.01.004. Epub 2012 Feb 17.
Choanoflagellates are closely related to metazoans and fungi according to recent phylogenetic studies; therefore the systematics of these organisms is of particular interest. The choanoflagellate morphospecies Codosiga botrytis is the first described choanoflagellate, and is one of the most frequently reported choanoflagellate species. In this study we present phylogenetic and morphological data on eight different strains of Codosiga botrytis. Among these there are five ancient strains; these cultures have been established from up to 43,000 years old cysts from Siberian permafrost. We found that based on the variable V4 region of the small subunit (SSU) of the rDNA, all the investigated freshwater isolates of Codosiga botrytis, together with Sphaeroeca volvox, form a cluster at the base of all other choanoflagellate species. Moreover, the morphospecies described classically as Codosiga botrytis contains at least four different genotypes separated by considerably high genetic distance. All these 'cryptic species' have identical general morphology and cell structure. Strains have a similar life cycle with several different life forms and large morphological plasticity. For the first time we were able to establish cultures from cryo-conserved cysts of choanoflagellates. The ancient strains did not differ significantly in partial SSU rDNA from the modern ones. Besides, no biogeographically pattern could be established. This fact and the low genetic distances of some strains from remote locations support the distribution of dormant stages via air.
根据最近的系统发育研究，领鞭毛虫与后生动物和真菌密切相关；因此，这些生物的系统发育特别有趣。领鞭毛虫形态种 Codosiga botrytis 是第一个被描述的领鞭毛虫，也是报道最多的领鞭毛虫物种之一。在这项研究中，我们提供了关于 8 种不同 Codosiga botrytis 菌株的系统发育和形态学数据。其中有 5 种是古老的菌株；这些培养物是从西伯利亚永冻土中 43000 多年前的休眠孢中建立的。我们发现，基于小亚基 (SSU) rDNA 的可变 V4 区，所有调查的淡水 Codosiga botrytis 分离株，连同 Sphaeroeca volvox，在所有其他领鞭毛虫物种的基部形成一个聚类。此外，经典上描述的形态种 Codosiga botrytis 至少包含 4 种不同的基因型，它们之间存在相当大的遗传距离。所有这些“隐种”都具有相同的一般形态和细胞结构。这些菌株具有相似的生命周期，有几种不同的生命形态和较大的形态可塑性。我们首次能够从冷冻保存的领鞭毛虫休眠孢中建立培养物。古老的菌株与现代菌株在部分 SSU rDNA 上没有显著差异。此外，没有建立生物地理模式。这一事实以及来自偏远地区的一些菌株的低遗传距离支持休眠阶段通过空气传播的分布。
