Sleigh M A
Department of Biology, University of Southampton, UK.
Tsitologiia. 1995;37(11):985-1009.
Heterotrophic free-living flagellates appear to provide the ancestry for all other eukaryote groups. Not only are the oldest surviving anaerobic eukaryotes flagellated protists, but also there appear to be survivors of a lineage of flagellate forms which could have been close to the sources of the main branches of eukaryote evolution. These 'stem' forms of flagellates developed more complex flagellation with anchoring fibres which became the main components of the cytoskeleton and supported the cytostome; by their phagotrophic activities these flagellates established symbiotic relationships, first with aerobic bacteria to form mitochondria, and later with various forms of prokaryotic and eukaryotic algal cells to form chloroplasts of a variety of types having different pigments, different structure and different food storage patterns. The specific patterns of flagellation, cytoskeleton, cytostome, secreted surface structures and cell aggregation into colonies enable groups of organisms to be recognised, whose most primitive survivors in almost all cases are heterotrophic flagellates. The current view of the phylogeny of eukaryotes suggests that heterotrophic flagellates have provided the origins of all major eukaryote groups, and that the phylogeny of these flagellates is the key to understanding the evolution of all eukaryotes. We anticipate that further rRNA analyses, supported by ultrastructural data, will confirm the central role played by these flagellates in eukaryote evolution.
异养自由生活鞭毛虫似乎为所有其他真核生物类群提供了祖先。不仅现存最古老的厌氧真核生物是有鞭毛的原生生物，而且似乎存在一个鞭毛虫形态谱系的幸存者，它们可能与真核生物进化主要分支的源头相近。这些“主干”形式的鞭毛虫发展出了更复杂的鞭毛结构，带有锚定纤维，这些纤维后来成为细胞骨架的主要成分并支撑着细胞口；通过它们的吞噬营养活动，这些鞭毛虫建立了共生关系，首先与需氧细菌形成线粒体，后来与各种原核和真核藻类细胞形成具有不同色素、不同结构和不同食物储存模式的各种类型的叶绿体。鞭毛结构、细胞骨架、细胞口、分泌的表面结构以及细胞聚集成群体的特定模式使得能够识别不同的生物类群，几乎在所有情况下，其最原始的幸存者都是异养鞭毛虫。目前关于真核生物系统发育的观点表明，异养鞭毛虫是所有主要真核生物类群的起源，而这些鞭毛虫的系统发育是理解所有真核生物进化的关键。我们预计，在超微结构数据的支持下，进一步的rRNA分析将证实这些鞭毛虫在真核生物进化中所起的核心作用。
