Differentiation of the four animal and the four vegetal blastomeres of the eight-cell-stage ofTriturus alpestris.

The 4 animal and 4 vegetal blastomeres of the eight-cell-stage ofTriturus alpestris were isolated and cultured for up to 12 days. Because of the difficulty of obtaining intact animal and vegetal blastomeres of the same embryo, we either cut off the vegetal blastomeres or sucked off the animal blastomeres. The culture of early embryonic amphibian cells is improved by the use of 50% Leibovitz-medium with added fetal calf serum providing a stable pH and optimal osmotic pressure.Isolated animal blastomeres differentiated to irregularly shaped ciliated epidermis. 30% of the cases showed small amounts of myotomes, notochord and neuroid cells in addition to irregular epidermis. The vegetal blastomeres formed trunk and tail structures but only 6% of all cases formed nearly complete head structures in addition.From the results we conclude that the vegetal blastomeres as well as the animal blastomeres of the eight-cell-stage are already determined as to their future fate. The possibility of partial regulation and the influence of asymmetric or irregular cleavage on the further development of isolated blastomeres is discussed.