Spermatogenesis in a vulnerable South American cervid, dwarf red brocket (Mazama rufina)

The brocket deer (Genus Mazama) is a highly diverse cervid group distributed from Mexico to Argentina, with a downward population trend. However, literature on the basic reproductive biology of the genus is scarce. This work aimed to study biometric, histological and stereological aspects of the testes of Dwarf Red Brocket (Mazama rufina). Testes from free-ranging adult brockets (n = 3) were retrieved from necropsies. Testes were histologically processed. From histological images, several stereological parameters were estimated, and seminiferous epithelium cycle morphology was described. Testes volumes were between 8.2 and 18.4 ml and weights from 8.3 to 19.4 g. Gonadosomatic index (% paired-testes weight to body weight) went from 0.17 to 0.64. The tubular cross-sectional diameter was 179.8 ± 2.8 µm. Estimated volume densities for parenchyma and interstitium were 78.8% and 21.2% respectively. There were (in millions/ml) 96.0 ± 13.1 germ cells and 37.7 ± 6.0 somatic cells. Specific cell densities were (all expressed in millions/ml) as follows: spermatogonia 13.1 ± 4.2; primary spermatocytes 43.1 ± 5.0; round spermatids 36.8 ± 8.0 (lower density near the caudal pole, p < 0.01); sustentacular (Sertoli) cells 16.8 ± 4.1 and interstitial endocrine (Leydig) cells 17.4 ± 3.4. Sertoli cell index (germ cells per Sertoli cell) was 6.72. Eight stages of the cycle were described, and frequencies estimated, resembling those of goats. M. rufina adult testis anatomy is similar to that of other cervids and domestic ruminants, with an apparently lower spermatogenic efficiency. This work is a first approximation to the physiology of the testis of M. rufina. Basic knowledge of the reproductive physiology of vulnerable species may allow biotechnological approaches for the restitution of animal populations.

Unique features of spermiogenesis in the Musky Rat-kangaroo: reflection of a basal lineage or a distinct fertilization process?

Previous research has found the mature spermatozoon of the Musky Rat-kangaroo to share many characteristics with other macopodoids, some phalangeroids and even the dasyurids. While there have been several studies published on the ultrastructure of the mature marsupial spermatozoon, there are only a few detailed studies on marsupial spermatogenesis. Furthermore, there have been no studies undertaken which combine the staging of the epithelial cell cycle with transmission electron microscopy to describe the ultrastructural changes in the developing spermatozoon during these stages. Such studies have the potential to be used in determining the required time taken for certain components of the spermatozoa to develop. During this study, eight stages of the seminiferous epithelium were observed and the ultrastructure of spermatogenesis was divided into nine phases. Maturational processes in the epididymides are also described. Among the features reported are: the formation of a unique acrosomal granule different from those reported in any other marsupial, the absence of contraction of the nuclear ring, a conspicuous acrosomal compaction process despite the almost 100% coverage of the dorsal nuclear surface and the retention of late spermatids within the seminiferous tubules until the early spermatids have developed to the nuclear protrusion phase.

Morphological characterization of the seminiferous cycle in the goat (Capra hircus): a histological and ultrastructural study

The cycle of spermatogenesis/seminiferous cycle was investigated in the goat testis using both light and electron microscopy techniques. Using the various cell associations and the accompanying changes in spermatid shape and location, the cycle was divided into eight (8) successive stages. The cycle began with the accomplishment of spermiation (stage 1) and ended with apical migration and close attachment of late maturation phase spermatids at the Sertoli cell apex accompanied by adluminal retention of residual bodies with dense staining inclusions (stage 8). The early stages of the cycle (stages 1-4) were therefore characterized by the presence of only one generation of spermatids, the second one appearing only after the division of secondary spermatocytes in stage 4. Consequently, stages 5-8 had two generations of spermatids; Golgi or cap phase as well as maturation phase spermatids. Although stages 5 to 7 appeared as distinct entities, stages 6 and 7 were rather short-lived and considered as continuations of stage 5. Therefore, the 8 stages of the cycle in the goat were further condensed into 6 main divisions. The duration of each stage was estimated by the frequency of occurrence in sections. Among these, stage 1 had the highest frequency (34%) followed by stages 5-7 (27%). Stages 8 and 4 had the shortest frequency (up to 9%) while stages 2 and 3 had 13% and 12% respectively. These results indicate that, like most domestic species, goats have a cycle of 8 stages with 6 main divisions, the longest being stage 1.

Postnatal development of ovine seminiferous tubules: an electron microscopical and morphometric study

Corresponding to the increasing testicular volume and the histological appearance of the testicular parenchyma, the postnatal ontogenesis of the ovine testis can be divided into five phases. During the prebubertal period (phases 1-III), seminiferous tubules are solid and contain supporting (pre-Sertoli) cells as well as up to three types of germ cells: prespermatogonia I, II and spermatogonia precursor cells. In phase I, only prespermatogonia I are present and can usually be observed at the center of the seminiferous tubules. During phase II, prespermatogonia I migrate towards the basal lamina, divide and become prespermatogonia II. Those prespermatogonia I which are not successful in establishing contact with the tubular basal lamina degenerate. In phase III, prespermatogonia II divide and differentiate into cells which function as stem cells for spermatogenesis. Morphometric data corroborate the assumption of two types of prespermatogonia in the postnatal prepubertal ovine testis. Prespermatogonia I have nuclear volumes of about 480 microns 3 and cellular volumes of about 1200 microns3. In prespermatogonia II both volumes increase to about 920 microns3 and 1800 microns3 respectively. Adult A-spermatogonia are significantly smaller and possess an average nuclear volume of about 340 microns3 and an average cellular volume of about 800 microns3. Concomitanty with the formation of the tubular lumen in puberty (phase IV), supporting cells differentiate morphologically into typical Sertoli cells. Developmental events in the germ cell population are not yet synchronized. Adulthood (phase V) is characterized by complete spermatogenesis with all stages of the seminiferous epithelial cycle.

Seasonal changes in the intertubular tissue of the camel testis (Camelus dromedarius)

The morphology and morphometry of camel testicular intertubular tissue are reported for different seasons of the year. The intertubular tissue occupies a comparatively large portion of the camel testis ranging from about 24% in autumn to about 39% in spring. The volume percentages of the different intertubular tissue constituents, namely Leydig cells, blood vessels, lymph vessels and various connective tissue components, also display clear seasonal changes. Early in winter, the intertubular tissue is richly vascularized by blood vessels (about 18% of the intertubular volume), whereas lymph vessels constitute only about 3%. This remarkable abundance of blood vessels coincides with the presence of voluminous and active Leydig cells that represent about 44% of the total. In spring, an immense expansion of the lymph vessels is observed (up to about 10% of intertubular tissue), but no change is seen in blood vessels. The Leydig cells in this season constitute only about 19% of the total. In summer, the vascular compartment occupies nearly the same volume as in early winter but with fewer blood and more lymph vessels. The Leydig cell volume percentage is markedly increased (39.3%) as compared with spring. In autumn, blood and lymph vessels record their lowest volume percentages (12% and 2.5%, respectively) and Leydig cell volume is also decreased as compared to summer. The Leydig cell morphology evidently points to two periods of elevated activity during the year. The first period occurs early in winter and is characterised by voluminous Leydig cells (average volume: 1614 microns3) with a well developed and highly organised SER. By spring, the cells are reduced in size (926 microns3) due to a decrease in the amount of SER. The second period of elevated Leydig cell activity is observed in summer and is again characterised by an increased cell volume (1420 microns3) as a consequence of SER development. In summer, however, the SER is not as highly organised as in early winter. The absolute number of Leydig cells per testis also shows clear changes from season to season, being lowest in autumn (3.68 x 10(9) cells) and highest in late winter and spring (6.04 x 10(9) cells). Thus, camel Leydig cells are subject to a permanent turnover. Degenerating Leydig cells are replaced the year round by undifferentiated fibroblastic precursors, whereas Leydig cell mitoses are a rare observation. The strongest waves of replacement seem to follow the peaks of increased Leydig cell activity and occur between summer and autumn as well as in late winter and spring.

Quantitative morphology of the ovine seminiferous epithelium

Ultrastructural features and morphometric values of ovine Sertoli and spermatogenic cells are reported with special reference to the 6 stages of the seminiferous epithelial cycle. Seminiferous tubules occupy about 83% of the testicular parenchyma. Average tubular diameter (about 275 microns) and epithelial height (about 95 microns) do not vary significantly during the cycle. From preleptotene to late diplotene the cellular volume of primary spermatocytes increases nearly five-fold; the nuclear volume increases three-fold in the same period. Secondary spermatocytes are observed exclusively during stage 4 of the seminiferous epithelial cycle. Due to partial cell necrosis and autolytic events, ovine spermatids lose a considerable amount of their cytoplasm during acrosome and maturation phases prior to spermiation. Sertoli cells occupy between 27.6% (stage 3) and 36.6% (stage 1) of the tubular epithelium. The average volume of a Sertoli cell varies between 6380 microns 3 (stage 2) and 7195 microns 3 (stage 4), the absolute surface area between 10550 microns 2 and 12305 microns 2. The irregularly contoured Sertoli cell nucleus contains a vesicular nucleolus and occupies about 7.5% of the cell. Mitochondria (about 5%) and smooth endoplasmic reticulum are other prominent organelles, but three-quarters of the Sertoli cell are taken up by cytoplasmic matrix with a well-developed cytoskeleton. Ovine Sertoli cells contain large basal lipid droplets, but no typical lipid cycle can be observed.