Fig. 6

Stage 7 (A–B′, E) and stage 8 (C–D′, F–F′′). In situ hybridization for the gene Popi-engrailed (A–D′) and confocal micrographs of fluorescent antibody staining against tropomyosin (E–F′′). Images with the same letters are different views of the same embryo. A–B′: First opisthosomal segment. C–D′: Second opisthosomal segment. E: Anterior half of a flat-mounted germ band (ventral view). Tropomyosin-positive cells occur at the head lobe and primordial limb buds. F: Anterior third of a flat-mounted germ band at stage 8 (ventral view). Stomodeum begins to form between cheliceral limb buds. F′, F′′: Optical sections at, respectively, 16 and 27 µm depth from the ventral surface of the same sample in F, showing tropomyosin-positive cells internal to each limb bud, and a coelomic space. A and P: anterior–posterior axis; arrowhead: stripe of engrailed expression marking the posterior border of opisthosomal segment; asterisk: dot of engrailed expression; black arrow: invagination site of neural precursor cells; blue circle: Hoechst (blue); white circle: bright field; yellow circle: tropomyosin (yellow); ch: cheliceral segment; L1–4: leg 1–4 segments; oc: ocular segment; pp: pedipalpal segment; st: stomodeum. Scale bars A–D′: 100 µm. E–F′′: 250 µm