ABSTRACT
The effect of destruction of some blastomeres on subsequent cleavage in vitro was investigated in the marsupial Antechinus stuartii. Blastomeres were killed by puncturing with a fine glass needle. The positions of the punctured and surviving blastomeres were recorded with respect to the yolk mass and defects on the shell membrane. Blastomeres were punctured in 2-cell, 4-cell, 14-cell, 16-cell and 22-cell embryos. Subsequent development of the embryos was followed in vitro. Embryos developed at a normal rate after destruction of some blastomeres. Puncturing of the shell, mucoid layer and zona pellucida, without damage to blastomeres, did not affect subsequent development. The embryos developed in accordance with the proportion of surviving blastomeres. Embryos with half of the blastomeres surviving developed as embryos with half the zona pellucida lined by blastomeres. Embryos with 1/4 of the blastomeres destroyed developed as 3/4 embryos. It is not known, without transfer into surrogate mothers, whether these fractional embryos were capable of developing into complete embryos.
