Species-specificity of acrosome reaction and primary gamete binding in echinoids

Abstract

The gametes of four echinoids were combined in four homologous and elevent heterologous crosses in which cross-fertilization did not occur. Acrosomal reaction, primary gamete binding, gamete membrane fusion, and sperm entry were observed in each of the homologous gamete combinations. In 9 of the 11 heterologous crosses, although sperm underwent a normal acrosomal reaction, primary gamete binding and gamete membrane fusion were never observed. These data support the previous suggestion that cross-fertilization is prevented by failure of heterologous sperm to undergo primary gamete binding to the vitelline envelope of ova.