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Fig. 5 | BMC Biology

Fig. 5

From: Lineage tracing shows that cell size asymmetries predict the dorsoventral axis in the sea star embryo

Fig. 5

Cell size asymmetries are not necessary to establish the dorsoventral axis in P. miniata embryos. Representative DIC images of 72 hpf larvae generated by blastomeres of dissociated embryos. A CTRL embryos (not manipulated). B, E, and F Larvae generated by Individual blastomeres of embryos dissociated at the 2- (B), 4- (E) or 8- (F, F’) cell stages. C, D Larvae generated by vegetal (C) or animal (D) quartets of blastomeres isolated at the 8-cell stage. This corresponds to the vegetal and animal halves of an embryo. Vegetal or animal identity was established according to the position of the polar bodies. G Phenotypes of larvae formed by isolated blastomeres at between 48 and 120 hpf. Blastula: no invagination; Gastrula: evident gut; Bipinnaria: mouth formed. n= 94 isolated blastomeres; 35 embryos; 2 experiments. H, I Removal of one small cell at the 16-cell stage. Zygotes were denuded of their fertilization envelope and raised at 16C until the 16-cell stage. No cell (H) or one small cell (I) was removed by micropipette aspiration. Embryos were raised at 16C to 72 hpf, fixed, stained with Draq5 and Phalloidin and imaged on a confocal microscope. Phenotype quantification shown on bottom right. n=33 embryos, 2 experiments. JM Cell size reduction. Representative confocal images of CTRL (J) or manipulated (L) larvae. One blastomere at the 8-cell stage was injected with DiI and immediately reduced in size by micropipette aspiration of cytoplasm. CTRL embryos were injected but not aspirated. Quantification of the angles formed by the injected clone and the sagittal plane of the larva at 72 hpf is shown in K (CTRL; n=18 embryos) and M (reduced; n= 11 embryos). Rayleigh test, ns, not significant. Scale bars: 50 μm

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