Fig. 1

Cell size asymmetries in early sea star embryos. A Representative images of sea urchin (Lytechinus pictus) and sea star (Patiria miniata, Patiriella regularis) embryos at the 4-, 8- and 16-cell stages. Embryos were injected with mRNA coding for a membrane-bound fluorescent protein (mYFP, mGFP) and fluorescently tagged histone (H2B-RFP, H2B-mCherry) and subsequently imaged live on a confocal microscope. The datasets were segmented using the Fiji plugin Limeseg and individual blastomeres rendered as 3D meshes. Scale bars: 50 μm. B Volumes of individual blastomeres normalized to embryo volume, calculated as the sum of the volumes of the 4 blastomeres at the 4-cell stage. For sea star embryos, animal and vegetal poles were assigned according to the position of the polar bodies, and for sea urchin they were assigned according to the position of the micromeres. An, animal; Vg, vegetal; Me, mesomere; Ma, macromere; Mi, micromere. C Ratios of largest to smallest cells’ volume at 16-cell stage in sea star embryos. L. pictus: n=119 cells, 5 embryos. P. miniata: n=180 cells, 8 embryos; P. regularis: n= 91 cells, 4 embryos