Fig 5.

Early embryogenesis of WT and sqv-7(null) mutant animals. Nomarski photomicrographs of a WT embryo (A–E) and a sqv-7 embryo (F–J) from a sqv-7(n3789) homozygous hermaphrodite. (A and F) Pseudocleavage (the constriction of the plasma membrane as indicated by arrows) is observed in the WT embryo but not in the sqv-7 mutant. Maternal (m) and paternal (p) pronuclei are indicated. (B and G) Pronuclear meeting. The space between the plasma membrane and the eggshell (indicated by brackets) in the WT embryo is not evident in the mutant. The ends of the mutant egg along the A-P axis are indicated by short vertical lines. (C and H) The start of nuclear division along the A-P axis. (D and I) First mitosis. The initiation of cytokinesis is visible in the WT embryo but not in the mutant. The cleavage furrow is indicated by arrows. (E and J) After the first division. The two daughter cells (AB, P1) are labeled in the WT. The sqv-7 mutant embryo contains more than two nuclei (indicated by arrows) in a single cytoplasm. (Bar = 10 μm.)