part of endocytosis single fertilization sperm entry biological_process An endocytosis process that results in penetration of the egg shell through the micropyle (a specialized anterior opening in the vitelline envelope) and entry of the entire sperm, including the surrounding plasma membrane and the sperm tail, into the egg cytoplasm. This step in fertilization is seen in Drosophila, where a plasma membrane fusion event between the sperm and the egg does not occur. GO:0035037