Movie 1.

Germ cell migration speed is reduced during development. Timelapse imaging of PGCs at the gonad region at 24–26 hpf (upper half) and at 34–36 hpf (lower half). PGCs were labeled by injecting nuclear tdTomato-encoding mRNA in Tg(kop:lifeact-EGFP) embryos at the one-cell stage.