How does the fertilization membrane form in sea urchin?

Answer 1

In sea urchins, the fertilization membrane forms shortly after sperm entry into the egg. Upon fertilization, cortical granules within the egg release their contents into the perivitelline space, which causes a chemical reaction that hardens the egg's outer layer. This process, known as the cortical reaction, results in the formation of a protective fertilization membrane that prevents polyspermy and provides a barrier to additional sperm. The membrane ultimately helps ensure proper development of the embryo.