Fig. 4 in How to build a larval body with less than a hundred cells? Insights from the early development of a stalked jellyfish (Staurozoa, Cnidaria)

Fig. 4 The dynamics of gastrulation: CLSM of phallacidin staining (a, h) and TEM (b–g, i–k). Embryos are oriented with the gastrulation pole (yellow arrowheads) down. Prospective ectoderm cells are artificially colored in green and prospective endoderm cells are artificially colored in purple on the TEM images. (a–a‴) Successive stages of gastrulation, central optical sections. Note the columnarized (a) and then bottle-shaped (a′–a‴) presumptive endoderm cells marked with asterisks and stretching ectoderm cells (green arrowheads) adjacent to the site of ingression. (b) An embryo at the early gastrula stage (corresponds to a′). Presumptive ectoderm cells situated near the ingressing cells are stretched towards the pole of gastrulation, while the cells beyond this area have a cuboid shape. (c) Close-up of the region framed on B showing ultrastructure of an ingressing cell. White arrows demonstrate the constriction of the cell apex. A purple arrow shows the direction of squeezing of the enlarged basal portion of the cell inside the embryo and a green arrow shows the