Dispersal of sperm surface antigens in the plasma membranes of polyspermically fertilized sea urchin eggs

Polyspermically fertilized Strongylocentrotus purpuratus eggs were fixed at varying times after insemination and exposed to a monoclonal antibody (mAb J18/29) directed against a group of sperm surface antigens. Indirect immunofluorescence microscopy reveals that the sperm surface components recognized by mAb J18/29 are quickly incorporated into the egg plasma membrane and begin to disperse as early as 1.5 min after insemination. At subsequent times after insemination, they undergo further dispersal so that by 45 min they are distributed evenly over the entire surface of the egg. These results provide evidence for the free lateral mobility of sperm membrane components in the fertilized egg.