Fig. 2

Overview of the embryonic development of Phrynus marginemaculatus. Maximum intensity projections of Z-stacks of embryos imaged with nuclear staining (Hoechst) fluorescence. a–e Five embryonic stages, in ventral view, spanning the elongation of appendages, and showing germ band inversion and development of the ventral midline. f–h Head development, frontal view. f Undifferentiated head lobes. g Head lobe with neuron precursor cell invaginations. h Head lobes with anterior rim folding (semi-lunar grooves). i–k Opisthosomal development, posterior view. i Embryo with one opisthosomal segment. j Embryo with five opisthosomal segments. k Embryo with ventrally curved opisthosoma and most opisthosomal segments formed (number unclear). l, n Lateral organ formation and opisthosomal curving, lateral view. l Lateral organ as an undifferentiated bud proximal in leg II. m Lateral organ with a discreet “C” shape, and opisthosomal segments curved up. n Lateral organ in its final “kidney” shape, and opisthosoma curved ventrally. Insets in l–n show the lateral organ (Lo), which is outlined with dashed lines in the respective main panel. Dashed lines on the posterior regions of the embryos in l–n mark the curvature of the opisthosoma. o–q Deutembryo, in frontal, ventral and lateral view, respectively. Ch chelicera, Gz growth zone, H head lobe, Iv neural precursor cell invagination, St stomodeum. Scale bars: 500 µm