The fates of the blastomeres of the 16-cell zebrafish embryo.

We present a fate map for the 16-cell-stage blastomeres of the zebrafish embryo Brachydanio rerio. We injected high molecular weight fluorescent dextran into cleavage-stage cells to observe the contributions of the descendants of the first 16 cells to the adult. The patterns derived from these early cells are similar, but not identical among different embryos. Furthermore, two-color injections showed that sister blastomeres at the 16-cell stage regularly contribute to different sets of adult structures. A few of the scored tissues could not be mapped in a manner consistent with the predicted axes. Other tissues were mapped to several of the 16 blastomeres. Many of the tissues map with high probability to a few 16-cell-stage blastomeres. Thus, based on 112 injections in 56 different embryos, we have constructed a fate map by assigning probabilities for the contribution of each blastomere to each of 31 tissues in the 26-hour embryo.