events: dorsal closure of epidermis and midgut
Stage 15 lasts for 1 h and 40 min (11:20-13 h). Dorsal closure and dorsal epidermal segmentation are accomplished during this stage.
The gut forms a closed tube and completely encloses the yolk sac. In lateral aspect, the gut shows a first constriction; two further constrictions appear towards the end of stage 15. At the end of stage 14, the dorsal epidermis has completed fusion at anterior and posterior, but not at middle, levels. At the end of stage 15, dorsal closure is complete. After being covered by the overgrowing dorsal epidermis, the cells of the amnioserosa enlarge considerably, round up and disaggregate, finally becoming internalized.
Head involution continues and by the end of stage 15 the tip of the advancing dorsal ridge will reach approximately 85% egg length (0% egg length = posterior pole). Condensation of the ventral nerve cord begins.
Stage 15, in vivo (0.9 MB)
Stage 15, sagittal sections (0.3 MB)..........additional information
Stage 15, virtual microscope, sagittal sections..........additional information
Stage 15, anti-Crumbs..........additional information