Reconstruction of Starfish Eggs by Electric Cell Fusion: A New Method of Detect the Cytoplasmic Determinant for Archenteron Formation

A method of detecting cytoplasm carrying the determinant for archenteron formation in starfish was established. Animal egg fragments (AEFs) which had been severed from the vegetal halves were fused electrically into pairs with fragments prepared from various regions of immature oocytes. It has been previously shown that the vegetal halves are exclusively endowed with the ability to form the archenteron; AEFs alone develop into so-called permanent blastulae. Eggs thus reconstructed were allowed to develop in order to assess the presence of the determinant in the added fragments. Only AEFs fused with fragments from near the vegetal pole of the oocytes formed the archenteron and developed into bipinnariae and juveniles. Comparison between the inner and outer (including cortex) cytoplasm of small vegetal fragment showed that the outer cytoplasm gave the reconstructed egg a greater ability to form an archenteron than the inner cytoplasm.