Fig. 1. fue embryos undergo several rounds of anucleate cleavage. Fixed wild-type (A) and fue (B) embryos at the eight-cell stage, labelled with DAPI to reveal nuclei (red) and fluorescein phalloidin to visualise the actin cytoskeleton (green). (C) A wild-type embryo at the sphere stage and (D) a living fue embryo shortly after it has arrested cleavage. In both cases development took place for the same period of time. In most of the fue embryos, the characteristic cleavage orientation pattern is not perturbed, and the cells progress through several cleavage cycles, indicating that the core cell cycle engine is not affected. (E,F) Unfertilized wild-type and fue eggs, showing that the sperm is required to initiate cleavage of the fue embryo as in the wild type.