Smaug protein persists in PGCs. Double immunostains of Vasa, a PGC marker, and Smaug in PGCs. (a-c) Smaug is enriched in PGCs when they form during developmental stage 4, 1.5 hours after fertilization. (d-f) Smaug persists in the PGCs at stages 9 and 10, as they sit in the midgut pocket 3-to-5 hours after fertilization. (g-i) Smaug persists as the PGCs migrate through the midgut epithelium at stage 10. (j-l) Smaug is still detectable at stage 11, 5-to-7 hours after fertilization, at which time the PGCs lie dorsally between the midgut epithelium and the overlying mesoderm. SMG, Smaug protein.