The program of and mechanisms of fertilization in the echinoderm egg

Abstract

Current research on the mechanisms of sperm-egg fusion, the block to polyspermy, and metabolic activation are described. A cinemicrographic analysis of fertilization reveals that fusion of sperm and egg occurs between non-motile gametes, indicating that the flagellar motion of sperm is not required. The block to polyspermy is reviewed, emphasizing recent work on the role of cortical granule protease in altering sperm receptors of the vitelline layer.Metabolic activation or derepression at fertilization is highly regulated and occurs in a definite sequence. The primary event appears to be release of intracellular Ca2+. The timing of metabolic derepression is different in starfish oocytes. Here, a part of the derepression occurs during maturation and another part at fertilization. © 1975 by the American Society of Zoologists.