STUDIES ON THE ACROSOME. III. EFFECT OF CALCIUM DEFICIENCY

Abstract

1. When sea urchin spermatozoa are suspended in Ca-free artificial sea water,a) they show no morphological change, except that there is a tendency for the middle piece to become "loose" and move around to the side of the nucleus;b) the sperm swim vigorously and attack the surface of unfertilized eggs as in normal sea water, but without being able to penetrate;c) they do not undergo the acrosome reaction on contact with glass or collodion surfaces.2. If "Ca-free" egg-water is added to such a sperm suspension,a) a regular, reversible agglutination reaction occurs, which, with strong egg-water, lasts 2-4 times longer than in a corresponding suspension in which the calcium content is adjusted to that of normal sea water;b) no acrosome reaction can be detected in spermatozoa thus agglutinated in the virtual absence of calcium;c) after reversal of agglutination, such spermatozoa show no reduction in fertilizing capacity when used to inseminate unfertilized eggs in sea water. This is in marked contrast to the sea water control, in which there is a significant loss in fertilizing capacity following agglutination.3. It is concluded that:a) the agglutination reaction and the acrosome reaction must be considered to be separate phenomena, both occurring in response to the stimulus of egg-water, but not causally interrelated;b) in view of the fact that fertilizing capacity is retained to the full extent by sperm suspensions in which the acrosomes remain intact, and is at least partially lost following mass acrosome reaction, this acrosome reaction must play an important role in the process of fertilization.