THE RÔLE OF ANTIFERTILIZIN IN THE FERTILIZATION OF SEA-URCHIN EGGS

¹ From the William G. Kerckhoff Laboratories of the Biological Sciences, California Institute of Technology

1. Acidification of sea-urchin sperm suspensions to below pH 6 or brief heating above 30° C. liberates into the solution the substance termed antifertilizin which is defined by four manifestations of its reaction with fertilizin; (a) neutralization and (b) precipitation of the latter, (c) agglutination of eggs, (d) formation of precipitation membrane on egg jelly.

2. The treatment results in a marked decrease in the fertilizing power even when the time and intensity of exposure are not sufficient to immobilize the sperm.

3. The rate of oxygen consumption of sperm, that had been exposed to mild acid- or heat-treatment, was found to be very little affected in comparison with the effect on the fertilizing power. Short extrapolation permits the conclusion to be drawn that a considerable reduction in fertilizing capacity can be obtained with no reduction of activity of the spermatozoa.

4. Injection of antifertilizin solutions into rabbits results in the production of an agglutinin for the intact sperm. This shows that the substance is a complete antigen and supports the views that it is a protein and a component of the surface of the spermatozoön.

5. Fertilization is inhibited by antisera to antifertilizin.

6. Antifertilizin is considered to be concerned in an initial (perhaps essential) step in the union of the gametes whereby the spermatozoön is entrapped by the complementary, specific reacting substance, fertilizin, on the egg; and the above inhibition experiments are interpreted on the basis of a decrease in the number of reacting groups available on the spermatozoön.