Figure 1

Prospective patterning stages in Rhodnius early embryogenesis. Nuclear staining for fixed embryos at the designated stages. Left and mid panel images are taken from the dorsal and ventral egg surface, respectively, unless stated otherwise. Drawings correspond to graphical representations of the stage in lateral views. (A) Cleavage stage embryo with nuclei at the periphery. (B,C) As the blastoderm develops, nuclei concentrate posteriorly (arrows) to form the germ rudiment (GR, grey in C). Serosal cells (Ser) are placed dorso-anteriorly. (D-F) During gastrulation, posterior invagination (P.Inv) of the GR takes places dorsally and (G-I) the germ band (Gb) extends anteriorly, while on the ventral surface the non-invaginated surface GR (grey in F) forms a horseshoe. Dashed lines in (F) and (I) correspond to the tissue under which the Gb invaginates. (J-L) Once gastrulation is complete, the head (H) and thorax (Th) regions are visible, as well as a growth zone (Gz) from which abdominal structures develop. (M-O) The embryo has grown to its full length. H and Th are segmented, but not the abdominal region (Ab). (P-R) Segmentation is complete. Ab is segmented. The abdominal caudal flexure is immersed in the yolk in (M-R) and consequently not visualized in superior optical sections. (S,T,V) Growth stages in dorsal views. Cuticle fluorescence adds to and takes over nuclear staining with time. (S) Thoracic appendages (T. app.) larger than head appendages. Maxilar appendages mx1 and mx2 are distinguished. (T,U) T. app. curved over ventral surface of the embryo. Mx1 and antennal appendages (An) grow. (V) Mx1 are hidden by An. Throughout the above stages the DV and AP axes of the embryo are inverted respective to the egg. (W,X) During katatrepsis the embryo moves backwards. As a result the embryo and egg axes coincide. Throughout stage 10 the embryo also undergoes dorsal closure. Egg anterior cap (AC); md: mandibule; C. lb.: cephalic lobes. Magnification Bar in (A) is valid for all panels.