Bolachas

Sperm entry triggers the elevation of the vitelline envelope, which quickly detaches from the egg membrane. The envelope hardens in a few minutes working as an efficient barrier to polyspermy. The male pro-nucleus initiates its migration after sperm entry.

The male pro-nucleus (red) migrates from the peripherical region to the center of the egg, where it meets and fuses with the female pro-nucleus (verde).