Fig. 13

Expression of NK2.2 at consecutive developmental stages in embryos of the onychophoran E. rowelli. Anterior is left in A, B, D and up in C, E, F, K, L; developing legs are numbered. Empty and filled arrowheads point to the medial and lateral domain in the ventral nerve cords, respectively. A Stage III embryo in lateral view. B Stage IV embryo in ventrolateral view. C Stage III embryo in ventral view. D Stage VI embryo in ventral view. E Stage IV embryo in ventral view. F Stage VI embryo in ventral view. G Cross section of a stage III embryo, dorsal is up. H Same cross section as in G stained with DAPI. I Cross section of a stage IV embryo, dorsal is up. J Same cross section as in I stained with DAPI. Dashed lines indicate developing nerve cords in G–J. K Stage IV embryo in ventral view, detail of the stomodeum. Arrows point to the domains on either side of the stomodeum. L Sagittal section of the head of a stage VI embryo, dorsal is right. Note the expression in the mouth cavity (arrows). Abbreviations: at, developing antenna; cl, cephalic lobe; de, dorsal extra-embryonic tissue; jw, developing jaw; lp, developing lip; mc, mouth cavity; ph, developing pharynx; po, proctodeum; sp, developing slime papilla; st, stomodeum; ve, ventral extra-embryonic tissue; vo, developing ventral organ. Scale bars: A: 200 µm; B, D: 500 µm; C: 50 µm; E–L: 100 µm