Otiwi1 is absent at the initial pairing stage when the micronucleus (MIC) begins meiosis (A), but accumulates in the old macronucleus (MAC) during mid-to-late pair formation (B). Otiwi1 is transiently present in both the cytoplasm and the developing macronucleus (called anlagen, AN) right after its formation (C), and localizes only to the anlagen in early exconjugants (D). (E) Otiwi1 signal decreases dramatically in late anlagen development, and the parental MAC is degrading. Arrowhead in (A) indicates a MIC undergoing meiosis and stained with α-tubulin. Green, Otiwi1; red, 4′, 6-diamidino-2-phenylindole (DAPI); white, α-tubulin. See also Figure S2.