Abstract
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.
Highlights
The ultrastructure of the oral apparatus is supposed to be significant for elucidating more recent common ancestry and might provide support for particular groupings of oligotrichean ciliates
Apomorphies related to the involvement of the adoral zone in locomotion of Oligotrichea, the formation of a circular adoral zone in choreotrichids, the jumping movements of several aloricate choreotrichids, or the development of the supposedly cumbersome lorica in tintinnids might emerge by comparing the few transmission electron microscopical studies in the hypotrich outgroup (Bazkowska and JerkaDziadosz 1978; Fleury et al 1985; Grain 1972; Grim 1972; Grimes 1972; de Puytorac et al 1976; Torres et al 1986), the oligotrichids, aloricate choreotrichids, and tintinnids (Bardele et al 2018; Grim 1987; Hedin 1975, 1976; Laval 1971, 1972; Laval-Peuto 1975, 1976; Laval-Peuto et al 1979; Sokolova and Gerassimova 1984; Wasik and Mikołajczyk 1991)
While the first part of our ultrastructural investigations on the model tintinnid Schmidingerella meunieri (Kofoid & Campbell, 1929) Agatha and Stru€der-Kypke, 2012 treated the somatic ciliature (Gruber et al 2018b), the present second part focuses on the oral apparatus, i.e. the adoral zone of membranelles, the endoral membrane, and their associated fibres
Summary
The ultrastructure of the oral apparatus is supposed to be significant for elucidating more recent common ancestry and might provide support for particular groupings of oligotrichean ciliates. While the first part of our ultrastructural investigations on the model tintinnid Schmidingerella meunieri (Kofoid & Campbell, 1929) Agatha and Stru€der-Kypke, 2012 treated the somatic ciliature (Gruber et al 2018b), the present second part focuses on the oral apparatus, i.e. the adoral zone of membranelles, the endoral membrane, and their associated fibres. It is the first detailed study in tintinnids and Oligotrichea in general
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
