Zlatogursky Vasily V
Department of Invertebrate Zoology, Faculty of Biology, St. Petersburg State University, Universitetskaja nab. 7/9, 199034, St. Petersburg, Russia.
Protist. 2016 Feb;167(1):51-66. doi: 10.1016/j.protis.2015.12.002. Epub 2015 Dec 30.
Centrohelid heliozoans are non-ciliary axopodial protists of uncertain affinities. Cell coverings (organic spicules, siliceous plate-scales and spine-scales) are the main character for their taxonomy. Phylogenetic reconstructions of this group are mostly based on the sequences of 18S rDNA. Here molecular and microscopical data on Raphidiophrys heterophryoidea, R. drakena sp. nov., Spiculophrys agregata gen. et sp. nov. and four strains here referred to as Heterophrys-like organisms (HLOs) are provided. The family Raphidiophryidae is shown to be polyphyletic. The position of Spiculophrys is uncertain, but it probably represents the most basal branch in the order Pterocystida. Three strains of HLOs branch deeply inside the genus Acanthocystis and one strain inside Polyplacocystis, even though they differ considerably in morphology of the cell coverings from other members of these two genera. The possible reasons for this phenomenon are discussed. On the basis of newly obtained sequences and EDX-analysis an interpretation of the evolution of cell coverings is proposed. It appears that cell coverings were ancestrally organic, then silicified independently on two occasions and after that multiple cases of desilicification or even complete loss of coverings took place. So, in the two centrohelid orders the evolution includes similar sequences of parallel events.
中心太阳虫是亲缘关系不确定的非纤毛轴足类原生生物。细胞覆盖物（有机骨针、硅质板鳞片和棘状鳞片）是其分类学的主要特征。该类群的系统发育重建大多基于18S rDNA序列。本文提供了关于异形raphidiophrys、新种drakena R.、新属新种agregata Spiculophrys以及这里称为类异形虫（HLOs）的四个菌株的分子和显微镜数据。raphidiophryidae科被证明是多系的。Spiculophrys的位置不确定，但它可能代表了翼囊虫目的最基部分支。三株HLOs在棘囊虫属内分支很深，一株在多板囊虫属内分支，尽管它们在细胞覆盖物形态上与这两个属的其他成员有很大差异。讨论了这种现象的可能原因。基于新获得的序列和能谱分析，提出了对细胞覆盖物进化的解释。似乎细胞覆盖物最初是有机的，然后在两个不同的时期独立硅化，之后又发生了多次去硅化甚至完全失去覆盖物的情况。所以，在两个中心太阳虫目中，进化包括类似的平行事件序列。
