The combination of acrosome and
acrosomal vesicle formed the acrosomal system, usually referred to as acrosome.
The acrosome reaction consists of two steps--polymerization and lengthening of the acrosomal process with subsequent exocytosis of the
acrosomal vesicle, which exposes bindin; bindin then coats the acrosomal process and aids in sperm-egg attachment and fusion.
At an early stage of spermiogenesis, spherical acrosomal vesicles were found in a shallow depression of the nucleus (Fig.
Microtubules were regularly and diagonally arranged in the periphery near the acrosomal vesicles (Fig.
6), the acrosomal vesicles acquired a mature bell shape (Fig.
Sperm in contact with the jelly coat do not undergo an acrosome reaction involving exocytosis of the acrosomal vesicle, but in many instances they do undergo an elongation of the anterior portion of the acrosome [ILLUSTRATION FOR FIGURES 18, 19, 22 OMITTED].
The structure of the unreacted acrosome is similar to that described for some Patellidae (Hodgson and Bernard, 1988; Hodgson, 1995) but is closest to that of the Lottiidae (Hodgson and Chia, 1993), all of which are characterized by an acrosomal vesicle with an invaginated posterior lobe that protrudes into the subacrosomal space.
The lamprey, which is a cyclostome, has spermatozoa that carry a spherical acrosomal vesicle at the anterior end of their heads, subacrosomal material between the acrosome and the nucleus, and a long perforatorium rod through the nucleus (Follenius, 1965; Stanley, 1967; Nicander and Sjoden, 1971; Jaana and Yamamoto, 1981) [ILLUSTRATION FOR FIGURE 6B OMITTED].
The exocytosis of the acrosomal vesicle at several points in hagfish (our preliminary observation) as seen in higher vertebrates may be different from the acrosome reaction in sturgeon.