Abstract
By means of a transmission electron microscope, various types of intracellular vacuoles or vesicles were observed in ejaculated boar spermatozoa. These membrane bounded structures were frequently noticed in the head (acrosome and sperm nucleus) and the principal piece, but were hardly ever seen in the middle piece except in the cytoplasmic droplet, or in the end piece. In two cases of sterility (asthenozoospermia) and poor semen quality (hairpin curved deformity), the vacuoles appeared in the neck area, even in the center of proximal centriole, and some of them represented an invagination of the plasma membrane.
