Fig. 4.

Euperipatoides kanangrensis. A and C–G embryos stained with SYBR-green, (B) embryo stained with DAPI. (A) An embryo with the blastopore (between arrows) formed in the germinal disc (gd). The border between the germinal disc and the rest of the blastoderm (bd) is not sharp but nuclei start to become smaller and more densely packed within the germinal disc, compare both sides of white line. (B) The blastopore has elongated and the posterior (p) end can be distinguished from the anterior (a) by the former having a circular aggregate of cells (arrowhead) surrounding the central pit (asterisk) and the latter is an elongated concentration of cells on both sides of a cell-free furrow (arrow). (C–E) The anterior–posterior axis is, at the early germ band stages, not fixed in relation to the long axis of the egg. (F) An embryo with eight somites formed as indicated by the segmental grooves (arrowheads). The blastopore has been split up into three parts, the mouth (m), a middle opening (mo), and the proctodeum (pd). The first somite, the antennal segment, (s1) has already started to grow considerably larger than the following jaw (J) and slime papilla (sp) somites. (G) An embryo with approximately 15 segments out of a total of 18 formed. The brain lobes have formed as a result of extensive cell proliferation of the neuroectoderm that covers most of the segment. The split germ band is separated by dorsal and ventral extra-embryonic ectoderm (dee and vee). Scale bars = 250 μm. Anterior is to the top in panels F–G otherwise as indicated in the images.