When do sperm of the sea urchin, Pseudocentrotus depressus, undergo the acrosome reaction at fertilization?
D000177:Acrosome / Q000502:physiology; D000818:Animals; D005260:Female; D005306:Fertilization; D008297:Male; D012617:Sea Urchins; D013084:Sperm-Ovum Interactions; D013094:Spermatozoa / Q000502:physiology*