INITIAL-STAGES OF SPERM PENETRATION INTO THE EGG OF FUNDULUS-HETEROCLITUS

Very little information is available about the morphological details of sperm‐egg fusion in teleosts. The acrosomeless teleost sperm gains access to the egg cytoplasm through a small opening (the micropyle) in the egg envelope (the chorion). Identification of the micropyle, therefore, permits one to localize the sperm entry site and to use the electron microscope to study the details of sperm‐egg fusion under normal monospermic conditions. In this study freshly stripped eggs of Fundulus heteroclitus were inseminated with sperm of the same species and exposed to fixative at intervals varying from 1 second to 15 minutes after insemination. The scanning electron microscope was used to observe morphological aspects of the initial stages of fertilization. Copyright © 1979 Wiley‐Liss, Inc., A Wiley Company