Ultrastructure of goat testes: centriolar adjunct in spermiogenesis

During the morphological study of goat spermatogenesis, cross and oblique sections of the neck region (connecting piece) of the spermatid were closely studied in conjunction with the shaping of the sperm head; the centriolar adjunct (CA) briefly appeared as a fragile organelle in spermiogenesis. As is the case of other mammalian spermatids, the CA expanded about 1 microns in length from the distant end of the proximal centriole (PC). The prolongation of this structure began in an early stage of the cap phase in spermiogenesis, and it usually oriented itself parallel to the flat plane of the flattening spermatid head. In other words, the CA appears to regulate the flattening direction of the spermatid head. Thus, the expanding direction of this structure showed a declination of about 25 degrees C toward the ninth microtubule in the axoneme of the sperm tail. After regulating the head shape, this accessory apparatus quickly disappeared during the maturation phase. If this observation is correct and not an artifact of sampling procedures, the basic mechanisms of sperm motility might be elucidated.