Nuclear elongation is significantly reduced in embryos from kur^fs-kur. There is no visible defect prior to cellularisation in kur^fs-kur embryos when compared to wild-type embryos. The nuclei of kur^fs-kur mutants start to elongate normally in the first half of cellularisation. When the invaginating membrane front reaches the basal outline of the nuclei the first retardation compared to the wild-type situation is observed. The nuclei accomplish only approximately 60% of the length of wild-type nuclei does not move basally at the end of cellularisation. In contrast to the wild-type situation, kur^fs-kur nuclei do not move basally at the end of cellularisation. During gastrulation, kur^fs-kur embryos fail to form the cephalic furrow and do not accomplish germband extension.