Fig. 3

Cell cleavage and gastrulation periods. a–j Face view of a two-cell stage (3.25 hpf) at the animal pole of the embryo (AP animal pole, VP vegetative pole). b Height-cell stage (5.5 hpf), c 32 cells stage (8 hpf), d 128 cells stage (9.5 hpf), e 512 cells stage (11.5 hpf), f high blastula (14.25 hpf), g 30 %-epiboly stage (25.75 hpf), h 50 %-epiboly stage (31.25 hpf). The antero-posterior AP and dorso-ventral DV axes can be determined for the first time. The arrowhead highlights the posterior part of the germring. i 90 %-epiboly stage (40.25 hpf). The arrowhead highlights the posterior part of the germring. j Embryo at the beginning of the somitogenesis (4–6 somites, 64 hpf), Embryonic axes are well defined, the arrowhead shows optic capsules. k Embryo during the O1 period. (81 hpf). l Detail of Kupffer’s vesicle (arrowhead), (52.75 hpf). m Detail of the somites (stars) (64 hpf). n The yolk syncytial layer with numerous nuclei (arrowhead) (Ld) lipid droplet. The scale bar represents 250 µm (a–m) and 100 µm for n