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Fig. 2 | BMC Biology

Fig. 2

From: From spiral cleavage to bilateral symmetry: the developmental cell lineage of the annelid brain

Fig. 2

The stereotypicality of episphere development. a The comparison of the cell lineage trees of three larvae at 30 hpf. Blue branches in the lineage trees of embryo 3 represent the early developmental lineage (0–6 hpf) described in previous study [23], but not captured by the live-imaging movies in this work. Corresponding cells/divisions conserved in all three larvae are colored in black. The divisions and cells that do not occur in all three larvae are color-coded according to the legend. b The snapshots of the Z-projection of the live-imaging movies showing the differences between the three larvae at different time points. Differences are color-coded as in panel a. c Quantification of differences among embryos. The total number of differences represents the number of cells that are not present in the other two embryos at a given time point. The differences start to appear around 16 hpf and increase with time, reaching around 10% of the total cell number in the episphere at 30 hpf. d A cut-out from the consensus lineage tree (Additional file 10: Figure S2) illustrating the annotation system: The reference IDs (examples in blue boxes) are unique identifiers of each cell throughout the lineage tree and track files. Each division produces two daughter cells, whose lineage name is extended by a “1” (or “a”) or “2” (or “b”). The letter of extension is given at the edge connecting the vertical line (representing the division point) and the horizontal branch (green arrows). Using this system, the full lineage name can be read out from the consensus lineage tree. The red arrow at the division point indicates the number of embryos in which the given division occurred (max. 3). If the division occurred in only 2 out of 3 embryos, the subsequent branch lines are shaded in gray, instead of black color

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