The role of the cortical granules in the formation of the fertilization membrane in eggs from Japanese sea urchins. I

Abstract

1. 1. Strongylocentrotus pulcherrimus, Anthocidaris crassipina, Mespilia globulus, Pseudocentrotus depressus, Clypeaster japonicus, and Peronella lesueuri were examined concerning the behavior of the cortical granules in the formation of the fertilization membrane. 2. 2. In the eggs of Clypeaster japonicus, the cortical granules are differentiated into two optical parts of light and dark, when observed by a phase contrast microscope (dark contrast). 3. 3. Following the attachment of a spermatozoon, the granules explode and change into large globules. The granule explosion begins from the attachment point of the spermatozoon and spreads in a wave-like fashion. 4. 4. With this change, the globules are ejected, and the vitelline membrane is separated from the egg surface. 5. 5. The globules adhere to the rising vitelline membrane, gradually combining with it and giving rise to the fertilization membrane. 6. 6. When the vitelline membrane is weakened by proteolytic enzymes, the globules are squeezed out through the membrane, which remains attached to the egg surface. After several minutes, rod-like precipitates are formed in the globules. 7. 7. Ca-ion is necessary for the hardening of the fertilization membrane and also for the formation of the “rods.” 8. 8. It is suggested that the substance responsible for the hardening of the fertilization membrane is the same as the substance of the rods. 9. 9. The hatching enzyme of Strongylocentrotus pulcherrimus acts specifically on this substance.