Fig. 5

Early stages of notochord and tail development in F. borealis. A Optical sections showing an embryo at the tailbud stage, with notochord cells stacked along the AP axis (orange dots). Full dots mark notochord nuclei, open dots mark nuclei visible in other sections. B Embryo at the end of notochord cell divisions. The closeup shows the caudal ganglion primordium. C Embryo immediately after hatching. Closeups show the anterior end of the trunk with the mouth primordium (white asterisk) and detail of the tail with notochord and muscle cells. cg, caudal ganglion; ep, epidermis; mu, muscle cells. Scale bar, 10 microns