Fig. 6

Summary of fates and spatial domains of the first, second, and third quartets in the pilidium larva. Lineage diagram on the left exhibits all cells whose fates were directly tracked in this study—1q¹², 1q², 2q, 3q—as colored nodes. We do not report data from 1q¹¹, which is inferred by the difference between 1q¹ in C. lacteus [25] and our account of 1q² and 1q¹². We also do not report data from 4q, but have confirmed the result reported in [25] pertains to M. alaskensis (data not shown). AO, apical organ; BCR, buccal ciliated ridge; epi., episphere; hypo., hyposphere; ICB, inner ciliated band; L/A, L/P, R/A, and R/P, left versus right, anterior versus posterior; PCB, primary ciliated band. Diagrams to the right depict the episphere from apical view and the hyposphere in oral view (handedness as indicated) with spatial domains for each marked cell, as inferred from Additional file 1: Fig. S1 and other data. Thickened outlines indicate portions of PCB (episphere view) or ICB and BCR (hyposphere view). For simplicity, foam cells, nerves, and muscles are omitted. Also, in the anterior and posterior lobes, contributions of 2b and 2d to the PCB are not depicted directly. In most regions, the PCB consists of several rows, including a single-row backing band with short cilia, two or three rows of heavily ciliated mainline cells, and an interband of sparsely ciliated cells interspersed with monociliated collar cells. In the right anterior and left posterior lobes, thin strips contributed by 1a² and 1c², respectively, appear to consist of backing band, whereas one or two rows of mainline cells are derived from 1b¹² and 1d¹² in the same zones. 2b and 2d also contribute to mainline cells, as well as the interband. (There is no ICB on the anterior and posterior lobes.) Note also that, as with any cartographic projection, the relative areas occupied are distorted by the imposed stretch