COMPARATIVE-STUDY OF BOAR SPERM COMING FROM THE CAPUT, CORPUS, AND CAUDA REGIONS OF THE EPIDIDYMIS

Sperm quality in the caput, corpus, and cauda regions of the epididymi s of healthy and sexually mature Landrace boars was studied. Epididyma l sperm characteristics were examined by light microscopy (LM), scanni ng electron microscopy (SEM), and transmission electron microscopy (TE M). Sperm vitality decreased very slightly although progressively with the transport of sperm through the epididymis. Osmotic resistance of acrosomes was very low in the sperm from the caput and similar to 100% in the corpus and cauda. The incidence of spermatozoa with the head d etached from the tail remained stable in the first two regions of the epididymis, increasing notably in the cauda. Sperm agglutination incre ased progressively as sperm progressed along the epididymal duct. The percent of mature spermatozoa and aberrant spermatozoa increased from the caput to the cauda, whereas the percent of immature spermatozoa de creased. In the caput and corpus the percent of immature spermatozoa w as similar, although in the caput they were characterized by the prese nce of a proximal cytoplasmic droplet; in the corpus the cytoplasmic d roplet was distal. The acrosomal protuberance was highly developed in spermatozoa from the epididymal caput, but its volume was considerably reduced in those from the epididymal cauda. The electron density of t he acrosomal content was lower in spermatozoa from the caput than in t hose from the epididymal cauda. The mitochondrial sheath of spermatozo a from the caput was made of voluminous mitochondria of unequal size, with a low electron-dense matrix. In the cauda region, the mitochondri a were smaller in diameter, homogeneous in size, and with greater matr ix electron density. This last fact is related to the loss of the capa city of spermatozoa to fold their tail by the midpiece as they progres s along the epididymal duct. The complex epididymal maturation process of the sperm results in quantitative and qualitative changes that can be characterized in each of the three epididymal regions. The presenc e in the ejaculate of one or more gamete forms belonging to the epidid ymal caput, corpus, or cauda will allow workers to better establish th e intensity of stress produced by a high frequency of semen collection .