Fig. 4.

Two distinct cell-internalization events occur during early development in Hofstenia miamia. (A) Left: schematic depicting micromeres injected with fluorescent dextran (red triangles depict microinjection needles) at the four-cell stage when viewed laterally and from the vegetal pole. Right: time-lapse screen captures of fluorescent dextran-injected embryos when viewed from the vegetal pole (Movie 3). The daughter cells of micromeres labeled in red can be seen spilling over to the vegetal side and enveloping the macromeres (n=7). (B) Left: schematic demonstrating the distribution of cells injected with fluorescent dextran (red triangles depict microinjection needles) at the dimple stage when facing the dimple. Right: time-lapse screen captures of dye-injected embryos when viewed from the animal pole during the dimple stage (Movie 4). The patch of cells outlined by a dashed white line are gradually internalized during the dimple stage (n=7). (C) Schematic depicting the two cell-internalization events during Hofstenia development, with all micromeres and their progeny colored in red. Scale bars: 100 μm.