Fig. 1

Early D. maculatus embryogenesis. Photographs of D. maculatus embryos are shown, documenting key steps of nuclear division and early embryonic development. a DAPI nuclear staining of a 0–2 h AEL D. maculatus embryo. b–d, f, j–n Nuclear staining using SYTOX Green of D. maculatus embryos between 2 and 18 h AEL, as indicated. e, g F-actin phalloidin staining of 6–8 h and 8–10 h AEL D. maculatus embryos (recolored red). h, i Merge of DAPI (blue) and phalloidin (green). a White arrow indicates pronuclei. Red arrow indicates polar body nuclei. b Nuclei have divided and spread in the central portion of the embryo. c Nuclei continue to divide and migrate towards the egg surface. d Most nuclei have arrived the periphery of the egg. e “Cap”-like phalloidin staining suggests the arrival of nuclei at the surface. f Cells have rearranged as some are closely clustered together in the ventral posterior area. g “Furrow canal”-like phalloidin staining appears during this stage. h, i Fully cellularized embryo. White arrows indicate cells at telophase of mitosis on the egg surface. j The ventral furrow (vf) has invaginated and posterior amniotic fold (paf, red arrow) has appeared. k The germ band has coalesced and begun to extend towards the dorsal side of the embryo. Red dashed line indicates serosal window (sw). l An extending germ band stage embryo with bilateral head lobes. White arrowheads show segmental furrows. m Segmental furrows appear in more posterior regions as the germ band elongates (white arrowheads). n A fully elongated germ band with morphological segments and appendage primordia (red arrowheads indicate appendage primordia). Embryos were reared at 25 °C and photographed with Olympus SZX12, Leica 501007 or Leica SP5X confocal microscopy