Electric fusion of unfertilized starfish oocytes

An electric power device to fuse starfish oocytes was constructed. The outputs were supplied to a pair of parallel platinum wires in a solution of mannitol to which small amounts of salts were added. Oocytes of the starfish Asterina pectinifera, deprived of the vitelline envelope, were fused by several repetitions of a combination of 2.5 MHz AC field for a few seconds and a 50 micros DC pulse. Observation of fusing pairs of immature oocytes revealed that: (i) the oocyte placed near to the cathode forms a bulge at the surface facing the anode when subjected to DC pulses and, with subsequent DC pulses, a similar bulge is formed on another oocyte; and (ii) the pair of bulges then fuse together leading to fusion of the main body of the two oocytes. The conjugate of maturing oocytes soon became a single sphere, usually within 10 min, but this process toward spherical form paused when the oocyte was extruding its polar bodies. The conjugate of immature oocytes took 1 h to become a single sphere. The fusion did not disturb the progress of meiotic events, but electric pulses at an intensity suitable for the fusion often activated maturing oocytes and mature eggs.