(A) Quantification of polyhedral shape complexity of in silico isolated blastomeres at metaphase (using sphericity measurements of Imaris software). While blastomeres at the 2 cell stage have a similar sphericity than a spherical standard (standard: 0.975+/0.001 (n = 4); 2 cell: 0.950 ± 0.010 (n = 4)), from the 4-cell-stage on sphericity significantly decreases compared to standard (p<0.05, black asterisk). Average values are: 4 cell: 0.897 ± 0.013 (n = 8); 8 cell: 0.889 ± 0.009 (n = 8); 16 cell (vegetal): 0.846 ± 0.006 (n = 8), 24 cell (animal): 0.779 ± 0.007 (n = 8), 32 cell (vegetal): 0.851 ± 0.012 (n = 8); 44 cell (animal): 0.825 ± 0.012 (n = 8). Note that animal blastomeres (24 cell stage) have a significantly more complex polyhedral shape than their vegetal counterparts (16 cell) (p<0.05, red asterisk). An example of an in silico isolated blastomere is depicted above each bar of the graph. (B) Quantification of cell shape changes during the cell cycle at the 32–44 cell-stage. Left: 3D views of manually segmented blastomeres at interphase, prophase and metaphase (32 cell stage) showing cell shape changes between interphase, prophase and metaphase (inset: apical surface ratio of cell shown). Green is basolateral and red is apical. Scale bar as indicated. Top right: quantification of cell sphericity at interphase, prophase and metaphase. 6 blastomeres of the animal (red) and vegetal (blue) hemisphere of the 32 cell stage were averaged. The sphericity was significantly higher at metaphase than at interphase (black asterisk, p<0,05). Bottom right: quantification of the apical surface ratio at the same time points. The same blastomeres as in the sphericity graph were used to average apical surface ratio in the animal (red) and vegetal (blue) hemisphere. The apical surface ratio at prophase and at metaphase were significantly higher than at interphase (black asterisks, p<0,05). The apical surface ratio was higher in vegetal blastomeres than in animal ones (§ sign, p<0,05). (C) Pipeline for predicting spindle position using 2D computational model (Minc et al., 2011). See McDougall et al. (2015) for the full protocol of apical plane extraction. Top row shows examples of 3D rendered, in silico isolated blastomeres. Bottom row shows the extracted apical plane of the corresponding blastomeres with spindle predictions (blue circles joined by a green line). Scale bars = 20 µm.