Arp2/3 pathway enrichment at PM folds and tubules of the nascent cap. (A–E) Single sections at levels of folds (0 µm) and tubules (−1.5 µm) show pathway members coexpressed with PIP₂ probe at telophase 11. Corner brackets indicate nascent cap PM folds and tubules. (A) Spg-NG puncta localize at nascent cap PM folds and tubules, with the minimal signal at surrounding pseudocleavage furrows. Saturated eggshell signal at the base of Spg-NG image. 8/8 embryos. (B) Rac-GTP sensor enriches at nascent cap folds and tubules versus pseudocleavage furrows (arrows). 10/10 embryos. (C) SCAR-NG puncta localize at nascent cap folds and tubules, with minimal signal at pseudocleavage furrows. 6/6 embryos. (D) Arp3-GFP puncta localize to nascent cap folds and tubules, with minimal signal at pseudocleavage furrows. 7/7 embryos. (E) F-actin probe enriched at nascent cap folds and tubules versus lower levels at pseudocleavage furrows (arrows). 8/8 embryos. (F) Signal ratios at nascent cap folds versus pseudocleavage furrows, and tubules versus furrows, were measured at the same sites for PIP₂ probe and Rac-GTP probe and for PIP₂ probe and F-actin probe. Embryo values plotted.