Fig. 4

Expression of NK1 at consecutive developmental stages in embryos of the onychophoran E. rowelli. Anterior is up in A, A′, C, D, and left in B, E–J; developing limbs are numbered. Insets in A′ and B show the respective embryos stained with DAPI. A Stage I embryo in lateral view. Note the weak signal in the anterior segments (arrowheads). Inset shows the slime papilla segment and first leg-bearing segment in ventrolateral view. Filled arrowhead points to the transverse segmental furrow. A′ Same embryo as in A, superimposed light micrograph and DAPI image. Dashed lines demarcate transverse furrows. B Stage II embryo in lateral view. C Detail of the same embryo as in B in lateral view. Superimposed light micrograph and DAPI image. Arrowheads indicate the position of transverse furrows. D Detail of stage II embryo in dorsal view. Arrowheads indicate the position of transverse furrows. E Late stage III embryo in lateral view. F Third to fifth developing legs of the same embryo as in E in lateral view. Note the U-shaped domain (asterisks) in all and an additional dorsal domain in the fourth and fifth legs (arrowheads). G Same embryo as in F in ventral view. H Stage IV embryo in lateral view. I Fifth to seventh developing legs of the same embryo as in H in lateral view. Note the U-shaped (asterisks) and an additional dorsal domain (arrowheads). J Same embryo as in H in ventral view. Abbreviations: at, developing antenna; cl, cephalic lobe; de, dorsal extra-embryonic tissue; js, jaw segment; jw, developing jaw; po, proctodeum; sp, developing slime papilla; ss, slime papilla segment; ve, ventral extra-embryonic tissue. Scale bars: A–C, J: 200 µm; E, H: 500 µm; D, F, G, I: 100 µm