Quantitative aspects of water buffalo (Bubalus bubalis) spermatogenesis.

In the buffalo, seminiferous tubules occupy about 82% of the testis. Spermatogenesis can be divided into 6 stages according to characteristic cellular associations in the seminiferous epithelium. A-spermatogonia have a volume of approximately 1,400 microns3 and the highest absolute mitochondrial volume of all spermatogenic cells. B-spermatogonia display cellular, nuclear and mitochondrial volumes of approximately half the values of A-spermatogonia. From preleptotene (approximately 470 microns3) to late diplotene (approximately 2,300 microns3), the volume* of primary spermatocytes increases nearly five-fold; their nuclear volumes increase by 3.5 times within the same period. During zygotene mitochondrial cristae start to dilate. Grouping of mitochondria by a dense intermitochondrial substance is most prominent during pachytene and diplotene. In pachytene the absolute size of the Golgi apparatus more than doubles, indicating a high secretory activity. Through zygotene only rER is encountered; in pachytene and diplotene a tubular sER makes its first appearance. Secondary spermatocytes are found only in stage 4 of the cycle. Due to partial cell necrosis and autolytic events, late maturation phase spermatids display no more than 25% of the size of cap phase spermatids. There is no morphological evidence for an active uptake and digestion of residual bodies by the Sertoli cells. Also, no lipid cycle is present in the buffalo seminiferous epithelium. Morphometric evaluations reveal that 63% of all theoretically possible germ cells disappear from the seminiferous epithelium during spermatogenesis. Heavy cell loss is observed in stage 4 of the cycle in the spermatogonial fraction as well as during the second meiotic division.