Fig. 7. Gastrulation movement in the MZ hdf (fgfr1) medaka mutant embryo. (A-J) Epiboly movement in the M (A-E) and MZ (F-J) mutants; the same embryo is shown at all stages in both cases. Dorsal views (animal pole is up) (A,B,F,G). Dorsal-vegetal views (C,D,H,I). Vegetal views (E,J). Dashed lines indicate the border between the blastoderm and the yolk sac. The arrow in J shows a narrow gap between the lateral marginal cells. Note that completion of epiboly in the MZ mutant occurs at the same time as in the M mutant except in the midline region (E,J). (K-R) Movement of the axial and lateral mesoderm cells of the MZ hdf (fgfr1) mutant. Axial (K) or lateral (N) mesoderm cells were labeled via the UV-mediated uncaging of DMNB-caged fluorescein-dextran at the shield stage (st. 14), and traced for anterior migration (L,M) and dorsal migration (O,P), respectively. Arrows in K and N indicate the embryonic shield. The white arrows in L,M,O,P indicate locations of the labeled mesoderm cells at 6 hours after uncaging. The yellow arrows in O,P highlight the enveloping layer. Initial labeling positions are represented by pink arrows in L,M,O,P. (Q,R) Graphs comparing the migration of labeled cells in M (blue) and MZ (red) mutant embryos. Anterior migration (Q) was quantified by the ratio of the length of labeled cells relative to the yolk sac diameter. Dorsal migration (R) was quantified by the angle between the central position of the labeled cells relative to their initial position at the shield stage.