The effect of the acrosome reaction on the respiratory activity and fertilizing capacity of echinoid sperm.

We have examined the relationship between the acrosome reaction, sperm respiration, and fertilization using gametes of the sea urchin Strongylocentrotus purpuratus. The results indicate that when sperm are exposed to jelly coat isolated from homologous eggs, the following sequence of events occurs: (1) Sperm undergo the acrosome reaction within 30 sec with little or no loss in their capacity to fertilize eggs; (2) by 60 sec there is a dramatic decrease in fertilizing capacity which stabilizes after 4 or 5 min at a greatly reduced level; (3) by 1.5 to 2 min a progressive decrease in the rate of mitochondrial respiration becomes detectable and continues for 8 to 10 min, finally stabilizing at a greatly reduced rate. This decrease in respiration rate is paralleled by a decline in sperm motility. The effects of jelly coat on the acrosome reaction, sperm respiration, and motility are species specific. From these results we conclude that sperm which have undergone the acrosome reaction retain full fertilizing capacity for a very short time. The rapid decline in fertilizing capacity is followed by a decrease in respiration rate and motility.