Fig. 9. Archenteron elongation requires Xdsh function during early but not late gastrula stages. Archenteron elongation is disrupted in dorsally and circumferentially injected embryos at mid-gastrula (A) (^***P<0.001; n=36 control, 30 dorsal, 21 circumferential) and late-gastrula (^***P<0.001; n=38 control, 52 dorsal, 23 circumferential) stages. The fraction of the archenteron (red arrowhead at anterior limit) overlain by the Xnot domain (yellow arrowhead) is very different between control and experimental embryos, demonstrating that the lengthening of the archenteron is proceeding in the absence of convergent extension. (C) Archenteron anterior expansion is not statistically different between Xdd1-injected embryos, at late gastrula stages.