Gruber Michael S, Weißenbacher Birgit, Agatha Sabine
Department of Biosciences, University of Salzburg, 5020, Salzburg, Austria.
J Eukaryot Microbiol. 2020 Jul;67(4):463-479. doi: 10.1111/jeu.12795. Epub 2020 May 11.
The ultrastructure of the oral apparatus is supposed to be significant for elucidating more recent common ancestry and might thus provide support for particular groupings of oligotrichean ciliates. The transmission electron microscopical study on mainly cryofixed Schmidingerella meunieri specimens provides the first detailed data for tintinnids and Oligotrichea in general. Ten new characters are included into the cladistic analysis. These features together with the very limited body of literature suggest that substantial changes in the oral ultrastructure correlate only with the formation of a circular adoral zone in choreotrichids. Despite homoplasious morphological and ontogenetic adaptations to the planktonic lifestyle in halteriid hypotrichs and oligotrichids, their oral apparatuses generally retain the plesiomorphic ultrastructure of the Perilemmaphora. The highly complex ultrastructure of the adoral zone is thus able to accomplish an extension in the zone's functionality without obvious changes; only the position of the adoral zone at the apical cell portion together with a globular to obconical cell shape are apparently crucial. Merely, minute apomorphies characterise the Oligotrichea and tintinnids, respectively. Tintinnids with derived somatic ciliary patterns possess distinct microtubular bundles connecting the oral apparatus with the myoneme in the peduncle.
口腔器的超微结构被认为对于阐明更近的共同祖先具有重要意义，因此可能为寡毛类纤毛虫的特定分类提供支持。对主要经冷冻固定的缪氏施米丁格虫标本进行的透射电子显微镜研究，总体上首次为铃壳虫类和寡毛类提供了详细数据。十个新特征被纳入分支分析。这些特征连同非常有限的文献资料表明，口腔超微结构的实质性变化仅与毛缘类中环形口围带的形成相关。尽管在弹跳类下毛类和寡毛类中存在对浮游生活方式的同形形态和个体发育适应，但其口腔器通常保留了围膜虫属的祖征超微结构。因此，口围带高度复杂的超微结构能够在不发生明显变化的情况下实现该区域功能的扩展；显然，只有口围带在顶端细胞部分的位置以及球状到倒锥形的细胞形状至关重要。仅仅有一些微小的衍征分别表征寡毛类和铃壳虫类。具有衍生的体纤毛模式的铃壳虫类拥有连接口腔器与柄中肌原纤维的独特微管束。
