Fig. 8. Cytokinesis defects in car-1(RNAi) embryos. Selected frames from a time-lapse Nomarski video recording (not shown) obtained from wild-type (A-H) and car-1(RNAi) (I-P) embryos. The relative time of each exposure is indicted in minutes. Anterior is to the left; black dots represent centrosomes; black arrowheads indicate cleavage furrows; white arrows indicate nuclei in the car-1(RNAi) embryo. Pronuclei appear in the anterior (maternal) and posterior (paternal) regions of the embryo (A,I). The maternal pronucleus migrates to the posterior of the embryo and associates with the paternal pronucleus (B,J). Pronuclei move towards the middle of the embryo before fusing (C,K). Wild-type embryos then initiate the first mitotic division: (C) late prophase; (D) anaphase; (E) appearance of cleavage furrows (arrowheads). The cell cycle continues, producing embryos of two (F), four (G) and six (H) cells. Defects in car-1(RNAi) embryos become apparent during the first cell division. Pronuclear fusion is delayed (K), and cleavage furrows begin to form (not shown) but subsequently regresses, giving rise to a one-cell-embryo containing two nuclei (N). During the next cell cycle cytokinesis is re-initiated and cleavage furrows develop (arrowheads, O), but again these regress coincident with the reappearance of the nuclei. Embryonic cell cycles that are coupled with abnormal cytokinesis continue, resulting in multinucleated cells (P; arrowheads, nuclei).