Rainbow trout chimeras produced by injection of blastomeres into recipient blastulae.

In mammals, the ability to successfully introduce isolated cells into a recipient embryo and to document their development has been an important experimental advance in determining the developmental potential of cells. These techniques are also useful in reestablishing the genome of embryonic cells into a germ line. The objective of the present study was to determine whether blastomeres isolated from rainbow trout (Oncorhynchus mykiss) will incorporate and continue to develop when injected into recipient embryos. In the first experiment, donor cells, previously labeled by injecting fluorescein isothiocyanate-dextran into the zygote, were isolated from blastulae; approximately 1000 of these cells were microinjected into each unlabeled recipient embryo of the same developmental stage. Following subsequent development through gastrulation, microscopic examination revealed that 19 of 114 injected embryos (17%) contained fluorescent cells. These labeled cells were present at numerous sites within embryos, and the pattern of distribution of these cells varied among embryos. In experiment two, blastomeres from normal diploid embryos were injected into triploid blastulae. The injected embryos were incubated until hatching and then sacrificed; cells from these embryos were dispersed and treated with 4',6-diamidino-2-phenylindole. The proportion of diploid cells, as determined by flow cytometry, varied from 2.0% to 12%. From these results we conclude that blastomeres isolated from rainbow trout blastulae will incorporate and continue to develop following injection into recipient embryos.