Fig. 2

Notch signalling controls the pinching off process of the rostral somites. a–b BfFringe expressed in the anterior endoderm (ventral part of the archenteron) and BfDelta was expressed in the presumptive rostral somites at the late gastrula stage. Blastopore views with the dorsal side up. The white dotted circle indicates the archenteron. s somite, ar archenteron. Scale bar, 50 μm. c–f Effect of 100 μM DAPT treatment on BfFringe (n = 7, 100 %) or BfDelta (n = 8, 100 %). Anterior views with the dorsal side up. g In the DMSO-treated control larval embryo, the segmental boundary between the somite and the dorsal gut roof was clear (n = 1). h In larval embryos treated with DAPT, the boundary was unclear and ectopic expression of Muscle-actin was observed (n = 1). Transverse sections with the dorsal side up. White arrowheads indicate somite and gut fusion locations. The white dotted circle indicates the border between the gut and somites