Hess Sebastian
Department of Botany, Cologne Biocenter, University of Cologne, Zülpicher Str. 47b, 50674 Cologne, Germany.
Protist. 2017 Feb;168(1):109-133. doi: 10.1016/j.protis.2016.11.003. Epub 2016 Dec 7.
The genus Hyalodiscus Hertwig and Lesser, 1874 comprises naked freshwater amoebae with a unique set of characters, namely a vibrant orange-red colour, a discoid or fan-shaped morphology, and a characteristic rolling locomotion. Some species feed on the chloroplasts of green algae and were regarded as relatives of Vampyrella Cienkowski, 1865. However, because of striking morphological differences and the lack of molecular data, the exact relationship of Hyalodiscus to vampyrellids is still obscure. Here, I describe Hyalodiscus flabellus sp. nov., a bright orange, fan-shaped amoeba feeding on Oedogonium (Chlorophyceae), which likely is a close relative of the type species H. rubicundus Hertwig and Lesser, 1874. Sequence comparisons of the SSU rRNA gene revealed that H. flabellus belongs to a deep-branching, so far uncharacterised lineage of the order Vampyrellida (Rhizaria), here defined as family Hyalodiscidae POCHE, 1913. Based on these results, the systematic position of the genus Hyalodiscus could be finally clarified, accompanied by the revision of relevant diagnoses and a taxonomic summary. Furthermore, the work reports on endosymbiotic bacteria inhabiting the cytoplasm of H. flabellus, which were identified as "Candidatus Megaira polyxenophila" (Rickettsiales, Alphaproteobacteria) using the full cycle rRNA approach with newly designed FISH probes for this widespread endosymbiotic bacterium.
透明盘变形虫属（Hyalodiscus）由赫特维希（Hertwig）和莱泽（Lesser）于1874年建立，包含一类裸露的淡水变形虫，具有一系列独特特征，即鲜艳的橙红色、盘状或扇形形态以及特有的滚动运动方式。一些物种以绿藻的叶绿体为食，曾被视为1865年西恩科夫斯基（Cienkowski）所描述的 Vampyrella 的近亲。然而，由于显著的形态差异以及缺乏分子数据，透明盘变形虫属与 Vampyrella 的确切关系仍不明确。在此，我描述了新物种扇形透明盘变形虫（Hyalodiscus flabellus），这是一种以鞘藻属（绿藻纲）为食的亮橙色扇形变形虫，它可能是模式种赤褐透明盘变形虫（H. rubicundus）（赫特维希和莱泽，1874年）的近亲。小亚基核糖体RNA（SSU rRNA）基因的序列比较显示，扇形透明盘变形虫属于 Vampyrellida 目（根足虫门）一个分支较深、迄今未被描述的谱系，在此定义为透明盘变形虫科（POCHE，1913年）。基于这些结果，透明盘变形虫属的系统位置最终得以明确，同时对相关诊断进行了修订并给出了分类总结。此外，该研究还报告了栖息在扇形透明盘变形虫细胞质中的内共生细菌，利用全周期rRNA方法，通过新设计的针对这种广泛存在的内共生细菌的荧光原位杂交（FISH）探针，将其鉴定为“嗜多宿主隐秘麦氏菌”（“Candidatus Megaira polyxenophila”，立克次氏体目，α-变形菌纲）。
