Fig. 2 in Ultrastructural Studies on a Model Tintinnid - Schmidingerella meunieri (Kofoid and Campbell, 1929) Agatha and Strüder-Kypke, 2012 (Ciliophora). I. Somatic Kinetids with Unique Ultrastructure

Fig. 2. Cross sections of dorsal dikinetids at different levels (from proximal to distal) in Schmidingerella meunieri in the transmission electron microscope. (A) The two basal bodies are sectioned at different levels, indicating a more proximal position of the anterior one. Arrowheads mark the electron-dense cuffs. (B) The dikinetid shows the electron-dense cuff (arrowhead) around the posterior basal body and the postciliary ribbon extending parallel to that of the more anterior dikinetid (arrow). (C) Slightly oblique section showing the three extraordinary microtubular ribbons extending perpendicularly or obliquely to the kinety axis leftwards: ribbons I and II originate near the posterior basal body, ribbon III commences near the anterior one. The arrow marks the long postciliary ribbon from the previous dikinetid. (D) The extraordinary ribbons I, II, and III are shown in cross sections. Note the fibrillar structure of the kinetodesmal fibril. (E) The dikinetid is located in a ciliary pit. While the anterior basal body terminates with a condylocilium, the posterior cilium displays a typical axoneme and is attached to the pit's left wall by a cytoplasmic connection (arrowheads). (F) The short condylocilium at the anterior basal body is not visible any longer. The ribbons II and III and the transverse ribbon terminate close to the cell cortex. I–III, extraordinary microtubular ribbons I–III; Axn, axoneme; Axs, axosome; CG, core granule; Co, condylocilium; CP, ciliary pit; D, desmose; Kd, kinetodesmal fibril; M, cell membrane; Pc, postciliary ribbon; T, transverse ribbon. Scale bars: 250 nm.