Oral development in WT Tetrahymena. (A) The structure of the OA. (A′) The course of cell division (tandem duplication). The following stages are shown from left to right: interphase, cell division stages 3 and 5, and cytokinesis. (A″) Stages of divisional oral development (based on Lansing et al. [1985]; Nelsen [1981]). See Table 1 for details. In panels A and A″ the subtypes of BBs are displayed as follows: filled circles; ciliated BBs, open circles; unciliated BBs, crossed circles; BBs destined for resorption. (B–K) SR-SIM images of WT Tetrahymena cells stained with 20H5 anti-centrin (red) and DAPI (blue). Insets show the OP region at a higher magnification. (B) Early stage 1a. (C) Late stage 1a. (D) Stage 1b. (E) A transition between stages 2 and 3. (F) A transition between stages 3 and 4a. (G) Stage 4b. (H) A transition between stages 4b and 5a. (I) Stage 5a. (J) Early stage 5f. (K) Late stage 5f. RB, ribbed wall of microtubules; OP, oral primordium.