Abstract
A spermiogram obtained from a boar was found to show separation of the head and tail in 100% of the spermatozoa. The ejaculated spermatozoa and the testes were investigated by light and electron microscopy. The mean proportions of heads and tails in ejaculated spermatozoa were 17.6 ± 3.0% and 82.4 ± 3.0%, and the ratio of heads to tails was 1: 4-5. The mean proportion of mottle spermatozoa was 23.8 ± 4.8%. Most of the tails had a cytoplasmic-like swelling in the middle piece. Ultrastructurally, the ejaculated spermatozoa lacked a basal plate in both the head and the tail, but no other ultrastructural abnormality was observed. The cytoplasm in the middle piece of the tail contained vesicular or tubular structures. The right testis in this boar was located in the scrotum, but the left testis was intraabdominal. Electron micrographs of the scrotal testis showed that the abnormalities were first recognizable in spermatids at the cap phase. Pairs of centrioles were not observed on the nuclear membrane at the caudal pole of the nucleus. Since the centrioles failed to approach the nucleus, it appeared that mechanical connection between the proximal centriole and the nucleus was not established. In addition, the basal plate was not formed on the nuclear membrane. The spermatozoa in the lumen of the seminiferous tubules showed separation of the head from the tail. From these results, it is concluded that the heads were already detached form the tails of the spermatozoa in the testis.
