Considerations on the Systematic Position of Uronychia and Related Euplotids Based on the Data of Ontogeny and 18S rRNA Gene Sequence Analyses, with Morphogenetic Redescription of Uronychia setigera Calkins, 1902 (Ciliophora: Euplotida)

Wei-Bo Song ； Norbert Wilbert ； Zi-Gui Chen ； Xin-Lu Shi

《Acta Protozoologica》 43卷4期 (2004/12) Pp. 313-328

並列摘要

Characteristics found in morphogenetic process of the Uronychia setigera Calkins, 1902 during binary division and the molecular data of several euplotid genera inferred from 18S rRNA gene sequence analyses are compared and discussed. The results indicate that the traditional order Euplotida might comprise 3 paraphyletic groups: the eueuplotids, i.e. euplotids with a 5-cirral anlagen mode and a subcortical origin of the oral primordium during morphogenesis (we call them the ”typical” euplotids in the text), gastrocirrhids (the pseudoeuplotids) and discocephalids, the last of which is possibly a convergent lineage. The results suggest also that Uronychia represents a primitive type within typical euplotids in phylogeny. Based on these analyses, a conclusion is suggested which consists of essentially the following points: (1) The traditional euplotids are likely a paraphyletic assemblage with differently originated groups. As a suggestion based on the new definition, the euplotids s. l. contains at least 2 subgroups: the eueuplotids and the sister group, gastrocirrhids (pseudoeuplotids) with multianlagen mode which is a divergent or apomorphic feature. (2) The systematic position of discocephaline remains unclear, but possibly an intermediate group between the euplotids s. str. and stichotrichs. We agree, however, that it is presently placed within the order Euplotida, as an outer group of other two assemblages. (3) The morphogenetic feature of 5-cirral-anlagen-mode is highly conservative and should be hence weighted with more phylogenetic value(s) in systematic analysis. (4) We suppose that some features like the origin mode of the leftmost frontal (formed from the UM-anlage), the situation of undulating membranes (e.g. two in number, curved in appearance) represent apomorphic features, and should not be over-evaluated, which caused often the diverse structures of the phylogenetic trees. (5) Euplotids s. str. might be derived from the 5-anlagen ancestor-type of hypotrichs s. l., which is possibly also the ancestor of the current stichotrichs.

並列關鍵字

18S rDNA gene sequences ； Ciliophora ； euplotids ； morphogenesis and phylogeny ； Uronychia setigera