Site of sperm entry and a cortical contraction associated with egg activation in the frog Rana pipiens.
D000818:Animals; D001001:Anura; D005260:Female; D005306:Fertilization; D008297:Male; D010063:Ovum / Q000502:physiology / Q000648:ultrastructure; D011894:Rana pipiens; D013084:Sperm-Ovum Interactions