Cycle of the seminiferous epithelium in the Java fruit bat (Pteropus vampyrus) and the Japanese lesser horseshoe bat (Rhinolophus cornutus)

The cycle of the seminiferous epithelium in the Java fruit bat, Pteropus vampyrus, and the Japanese lesser horseshoe bat, Rhinolophus cornutus, was investigated by light microscopy and the characteristics of spermiogenesis were compared between these two species. In the Java fruit bat, the cycle of the seminiferous epithelium was divided into 11 stages and developing spermatids were subdivided into 13 steps. While in the Japanese lesser horseshoe bat, the cycle of the seminiferous epithelium was divided into 10 stages and developing spermatids were subdivided into 13 steps. Excepting slight morphological differences, the characteristics of acrosomal formation in both species were almost similar with each other. In the Java fruit bat after stage VII, the acrosome gradually elongated, flattened and finally became scoop-like in shape. In the Japanese lesser horseshoe bat after stage VIII, the acrosome elongated, flattened and then slightly shortened. Before spermiation, the acrosome became long spatula-like in shape. The elongation and flattening of spermatids in these two species were similar to those in insectivores. The finding may reflect the fact that the order Chiroptera is phylogenetically close to the order Insectivora.     

Lectin-binding patterns in the spermatogenic cells of the shiba goat testis.

Lectin-binding patterns in the testis of the sexually mature goat were investigated by light and transmission electron microscopy. Dolichos biflorus agglutinin (DBA) and Griffonia simplicifolia agglutinin-I (GS-I) were negative in the seminiferous epithelium, but soybean (Glycine max) agglutinin (SBA), Griffonia simplicifolia agglutinin-II (GS-II) and peanut (Arachis hypogaea) agglutinin (PNA) were positive in the acrosomal vesicle of the Golgi-phase spermatids and in the acrosome of the cap-, acrosome- and maturation-phase spermatids. In addition, PNA was positive also in the plasma membrane and cytoplasm of the spermatogenic cells from the late pachytene spermatocytes to the maturation-phase spermatids. This finding indicates that glycoconjugates containing D-galactose residue appear at this period. Therefore, PNA may be a useful marker of developing spermatogenic cells. Electron microscopically, the positive reactions of SBA, GS-II and PNA were demonstrated in the central dense area (acrosomal granule) of the cap-phase spermatid acrosome, but not in the peripheral low-dense area. These results indicate that the lectin-bindings in the goat testis not only are common features, but also have patterns somewhat different from those in other mammals in such a way that GS-II can be detected in the acrosomal region of all phases of spermatids and that PNA is positive in the late spermatid acrosome.     

Ultrastructure of goat testes: tubulobulbar complexes between spermatids and Sertoli cells

The fine structure of tubulobulbar complex (TBC) of goat seminiferous epithelium was studied using testicular samples fixed by perfusion. During the maturation phase of the spermatid, the TBC appeared on the periphery of the head before spermiation, dorsal and ventral parts of the head, both sides of the acrosome and on the postnuclear sheath region. At an early stage of the development of the TBC, a partial loss of smooth endoplasmic reticulum in the ectoplasmic specialization of a neighboring Sertoli cell was observed; filament bundles disappeared and a small fragmented smooth endoplasmic reticulum was left. Subsequently, a spermatid vesicle (coated vesicle) expanded to be in contact with the Sertoli cytoplasm by a small channel. These tubular projections extended to form a bulbous balloon-like structure forming sometimes a bi-balloon appearance, until torn off from the spermatid into the Sertoli cytoplasm and probably digested by the Sertoli cell. The significance of this structural development was morphologically discussed.     

Morphological study of metaphase-specific apoptosis in MRL mouse testis

Apoptosis of male germ cells is a complex phenomenon in many animal species. Understanding its mechanisms could be useful in the diagnosis and therapy of male infertility. To examine the differences of distribution of apoptosis among mouse strains, the terminal transferase-mediated nick end labelling (TUNEL) method was employed. In the testes of MRL mice, many TUNEL-positive cells were identified at the metaphases of meiotic spermatocytes. Morphometrical analysis revealed that metaphase-specific apoptosis occurred at the region between secondary spermatocytes and step 1 spermatids in stage XII seminiferous tubules. In the investigation of the developing first-wave of seminiferous tubules, there were some metaphases showing apoptotic morphology prior to becoming secondary spermatocytes. Details of the apoptotic structure revealed by electron microscopy showed that cellular arrest occurred after the beginning of the M phase of the cell cycle. These results suggested that metaphase-specific apoptosis in the testis of the MRL mouse strain took place at least at the first meiotic division, perhaps showing the spindle assembly checkpoint of the cell cycle.     

Classification of the spermatogenic cycle,seasonal changes of seminiferous tubule morphology and estimation of the breeding season of the large Japanese field mouse (Apodemus speciosus) in Toyama and Aomori prefectures, Japan

The large Japanese field mouse, Apodemus speciosus, is a potential indicator of environmental stress, but this function has not been confirmed by histological studies. Since environmental stress affects the reproductive function of mice, we determined the reproductive characteristics of this species at two locations: Toyama (36°35ʹN, 137°24ʹE) and Aomori (40°35ʹN, 140°57ʹE). Mice were captured during May–November (n=119) and July–November (n=146) at these locations, respectively. We classified the breeding season from the numbers of pregnant females and young, in addition to the spermatogenic cycle and seasonal changes in seminiferous tubule morphology of males. Testicular weight was measured, and seminiferous tubule morphology was examined histologically. Fourteen stages were found in the seminiferous epithelium cycle based on acrosome formation and spermatid head morphology. At both locations, the breeding season peaked from late summer to early autumn and possibly in spring. Spermatogenic activity was classified into 4 periods from June to November: resting around June and October–November; resumptive around July; active around August; and degenerative around September. During the resting period, the seminiferous tubules consisted of Sertoli cells, spermatogonia and spermatocytes. Spermatogenesis began during the resumptive period, and spermatids were observed. During the active period, active spermatogenesis and a broad lumen were observed. During the degenerative period, spermatogenesis ended, and Sertoli cells, spermatogonia, spermatocytes and degenerating exfoliated round spermatids were observed. This study provides scientific information about the testicular histopathological evaluations of the large Japanese field mouse for its use as an index species of environmental pollution.     

Anatomy and Histology of the Male Reproductive Tract and Spermatogenesis Fine Structure in the Lesser Anteater (Tamandua tetradactyla,Myrmecophagidae, Xenarthra): Morphological Evidences of Reproductive Functions

The anatomy and histology of the male genital tract of the lesser anteater were studied. Fine details of spermatozoa regarding their genesis and morphology were also studied in six adult specimens. The testes lie in the pelvic cavity. The deferent duct emerges from the epididymis and opens into the ejaculatory duct, which drains into the membranous urethra. Accessory glands (prostate, seminal vesicle and bulbourethral gland) are histologically similar to those described in other mammals. The short penis presents an urethral orifice, while the corpus spongiosum becomes thinner at the end indicating the absence of a histologically defined glans. The seminiferous epithelium shows: (1) Sertoli cells with deep nuclear indentations, (2) spermatogonia with crusty‐like chromatin, (3) spermatocytes at different stages of maturation and (4) three morphologically distinct stages of spermatid differentiation according to nuclear shape, acrosome development and chromatin condensation. Sperm heads appear oval. The length of the spermatozoa averages 67.33 ± 1.60 μm. Two specimens with inactive spermatogenesis were azoospermic. Their testes and epididymis presented sizes smaller than those with active spermatogenesis. These studies together with others in anteaters may contribute to successful breeding in conservation programmes.     

Postnatal testicular development and actin appearance in the seminiferous epithelium of the Habu,Trimeresurus flavoviridis

The postnatal testicular development and actin distribution in the seminiferous epithelium were examined by light microscopy, using the testes of the Habu (Trimeresurus flavoviridis; snake) from 0-year-old to 3-year-old. At 0-year-old (about 1 month after birth), the testis was quite small in size, and the seminiferous epithelium was composed of only Sertoli cells and large spermatogonia. Actin immunoreactivity was observed in the peritubular myoid cells, but could not be detected in the seminiferous epithelium. At 1-year-old (about 10 months after birth), the testicular size increased to a great degree. In the seminiferous epithelium, spermatocytes newly appeared. Actin could still not be detected in the seminiferous epithelium. At 2-year-old (about 1 year and 10 months after birth), the testes continued to develop in size. In the seminiferous epithelium, elongate spermatids and round spermatids were frequently seen, in addition to Sertoli cells, spermatogonia and spermatocytes. Thus, active spermatogenesis was clearly recognized at this age. Moreover, the actin distribution in the seminiferous epithelium was observed at the site between Sertoli cells and spermatids, as well as that at adult stage. The immunoreactivity of actin in the peritubular myoid cells gradually increased from 0-year-old to 2-year-old. Conclusively, it seems likely that spermatogenesis in the Habu initiates at 2-year-old, accompanying with the appearance of actin in the seminiferous epithelium.     

Distribution of the sex chromosome during mouse spermatogenesis in testis tissue sections

During mammalian spermatogenesis, spermatogenic cells undergo mitotic division and are subsequently divided into haploid spermatids by meiotic division, but the dynamics of sex chromosomes during spermatogenesis are unclear in vivo. To gain insight into the distribution of sex chromosomes in the testis, we examined the localization of sex chromosomes before and after meiosis in mouse testis sections. Here, we developed a method of fluorescence in situ hybridization (FISH) using specific probes for the X and Y chromosomes to obtain their positional information in histological testis sections. FISH analysis revealed the sex chromosomal position during spermatogenesis in each stage of seminiferous epithelia and in each spermatogenic cell. In the spermatogonia and leptotene spermatocytes, sex chromosomes were distantly positioned in the cell. In the zygotene and pachytene spermatocytes at prophase I, X and Y chromosomes had a random distribution. After meiosis, the X and Y spermatids were random in every seminiferous epithelium. We also detected aneuploidy of sex chromosomes in spermatogenic cells using our developed FISH analysis. Our results provide further insight into the distribution of sex chromosomes during spermatogenesis, which could help to elucidate a specific difference between X and Y spermatids and sex chromosome-specific behavior.     

Vitamin A Deprivation Affects the Progression of the Spermatogenic Wave and Initial Formation of the Blood-testis Barrier,Resulting in Irreversible Testicular Degeneration in Mice

The blood testis-barrier (BTB) is essential for maintaining homeostasis in the seminiferous epithelium. Although many studies have reported that vitamin A (VA) is required for the maintenance of spermatogenesis, the relationships between the BTB, spermatogenesis and VA have not been elucidated. In this study, we analyzed BTB assembly and spermatogenesis in the testes of mice fed the VA-deficient (VAD) diet from the prepubertal period to adulthood. During the prepubertal period, no changes were observed in the initiation and progression of the first spermatogenic wave in mice fed the VAD diet. However, the numbers of preleptotene/leptotene spermatocytes derived from the second spermatogenic wave onwards were decreased, and initial BTB formation was also delayed, as evidenced by the decreased expression of mRNAs encoding BTB components and VA signaling molecules. From 60 days postpartum, mice fed the VAD diet exhibited apoptosis of germ cells, arrest of meiosis, disruption of the BTB, and dramatically decreased testis size. Furthermore, vacuolization and calcification were observed in the seminiferous epithelium of adult mice fed the VAD diet. Re-initiation of spermatogenesis by VA replenishment in adult mice fed the VAD diet rescued BTB assembly after when the second spermatogenic wave initiated from the arrested spermatogonia reached the preleptotene/leptotene spermatocytes. These results suggested that BTB integrity was regulated by VA metabolism with meiotic progression and that the impermeable BTB was required for persistent spermatogenesis rather than meiotic initiation. In conclusion, consumption of the VAD diet led to critical defects in spermatogenesis progression and altered the dynamics of BTB assembly.     

Analysis of various antigens in golden hamster testis by monoclonal antibodies.

A total of 38 hybridomas producing monoclonal antibodies (mAbs) was established by immunizing BALB/c mice with extracts of the golden hamster testis. Six mAbs stained the acrosome of developing spermatids by immunofluorescence. Two mAbs (1A11 and 4D8) reacted with spermatid components other than acrosome. The mAbs 1C9 and 4D3 recognized a 103 kilodalton (kDa) protein on immunoblots, and were reactive to spermatocytes and early spermatids, but not to late spermatids and spermatozoa. This finding suggests that the protein functions for meiosis or early spermiogenesis. Four mAbs (3G2, 2E5, 2G3, and 3F10) stained all stages of spermatogenic cells. The remaining 24 mAbs showed a positive reaction to the basement membrane of the seminiferous tubule. Two of them, 3D6 and 3E5, recognized approximately 150 kDa major proteins, indicating that the antigen is an extracellular matrix.     

Ultrastructure of the testis of Pekin ducks fed methyl mercury chloride: seminiferous epithelium

Testicular cells of Pekin ducks (Anas platyrhynchos) fed with 0 (control), 0.5 (group 1), 5 (group 2), or 15 (group 3) mg of methyl mercury chloride (CH3HgCl)/kg of basal feed for 12 weeks were examined by electron microscope. Sertoli's cells from ducks in group 2 had dilated smooth endoplasm reticulum, increased lysosomes, and large vacuoles, some with lipid droplets. Degenerative changes were more advanced in group 3 ducks. There were increases in lysosomes, myelinoid figures, vacuolations, cytoplasmic and nuclear debris, cristolyses of mitochondria, and distended Golgi's complexes, and a reduction in smooth endoplasm reticulum and microtubules when compared with those of the controls. Spermatogonia were resistant to CH3HgCl exposure, except in 2 ducks from group 3 which had cells that showed electron-lucent cytoplasm, abnormal mitochondria, and membrane-bound vacuoles. In primary spermatocytes, degenerative changes were evident in ducks fed the larger dose levels. In nuclei, synaptonemal complexes showed unpaired elements. In cytoplasm, cellular debris and vacuoles predominated. There was an increase in synchronized meiosis and apparent incomplete cell division. In ducks from group 3, the cellular damage was more severe and was present throughout the germinal epithelium. Spermatids differentiation was affected variably in groups 2 and 3. Severity of damage increased with the increased dosage of mercury. Where there was spermiogenic activity, the electron-dense acrosome granules, manchette, and midpiece were rarely found. Since the seminiferous tubules from 2 ducks in group 3 had severe destruction of spermatocytes and spermatids, the spermiogenic activity was negligible. Ingestion of CH3HgCl caused toxic injury to seminiferous tubules in groups 2 and 3 ducks. The degree of damage was related to the dietary amount of mercury.     

Ultrastructure of abnormal boar spermatid: acrosomic fragmentation and vacuolization.

The fine structure of acrosomic abnormalities such as fragmentation and vacuolization of boar spermatids was studied in 4 different breeds (Duroc, Hampshire, Landrace and Yorkshire). These abnormalities initially appeared from the cap phase of spermiogenesis. The acrosome did not consist of serial sac covering the hemispherical nucleus, but only of a large acrosomic vesicle containing a dense granule and several pieces of cleaved proacrosomic vesicles attached to the anterior half of the round nucleus. The abnormality was frequently observed in the sister cells connected with the intercellular bridge. In the same seminiferous tubules, there was another abnormality on the acrosomic vacuolization of limited membrane system. Multiple vacuoles or vesicles were seen in the apical part of the nucleus in the cap phase, and also in the lower part of the equatorial segment of the acrosome phase.     

Continual maintenance of the blood-testis barrier during spermatogenesis: the intermediate compartment theory revisited

Tight junctions occur between the lateral processes of neighboring Sertoli cells that divide the seminiferous epithelium into two compartments: basal and adluminal compartments. These tight junctions constitute the blood-testis barrier (BTB). The established theory that the BTB must open when spermatocytes translocate from the basal compartment to the adluminal compartment is marked by one contradiction, that is, normal spermatogenesis occurs in the testis because the BTB is expected to constantly seclude the adluminal compartment from the basal compartment in order to protect haploid germ cells from the autoimmune system. Subsequently, another concept was proposed in which two BTBs divide the seminiferous epithelium into three compartments: basal, intermediate and adluminal compartments. It has been suggested that the transition from the basal region to the adluminal region without the BTB open occurs through the agency of a short-lived intermediate compartment embodying some primary spermatocytes. In contrast, the results of recent findings in the molecular architecture of the BTB suggest that the BTB in the seminiferous epithelium must "open". In this paper, I re-examine the BTBs of boar and experimental cryptorchid mouse testes by transmission electron microscope (TEM). TEM analysis showed that an atypical basal compartment existed in the thin seminiferous epithelium of 14-day post-cryptorchid mice testes. In developmental boar testes, ectoplasmic specialization (ES) of the seminiferous epithelium showed dynamic behavior. The intermediate compartment was clearly observed between the basal and adluminal compartments of the mature boar seminiferous epithelium. ESs were observed between Sertoli cells and spermatids at all developmental stages, including early, late and mature. Furthermore, ESs were situated on the apical surface of the seminiferous epithelium. From these results, I propose that the BTB is continually maintained during spermatogenesis and suggest a model of ES circulation in the seminiferous epithelium.     

Sertoli Cell - Spermatid Tubulobulbar Complexes in the Ram

The fine structure of the tubulobulbar complex (TBC) of the ram seminiferous epithelium was studied in immersion-fixed testicular samples obtained in autumn (sheep's mating period). The TBC was visible during the last two stages of the seminiferous epithelium cycle. It originated as a tubular invagination of the Sertoli cytoplasm harbouring a complementary evagination from the spermatid head. Later, it expanded into a bulbous structure, finally becoming detached from the spermatid and apparently phagocytosed by the Sertoli cell. The significance of this transient structure is discussed and compared with previous reports for other eutherian mammals.     

A new ENU-induced mutant mouse with defective spermatogenesis caused by a nonsense mutation of the syntaxin 2/epimorphin (Stx2/Epim) gene

Repro34 is an N-ethyl-N-nitrosourea (ENU)-induced mutation in mice showing male-specific infertility caused by defective spermatogenesis. In the present study, we investigated pathogenesis and molecular lesions in relation to spermatogenesis in the repro34/repro34 homozygous mouse. Histological examination of the testis showed that the seminiferous epithelium of the repro34/repro34 mouse contained spermatogonia and spermatocytes but no round and elongating spermatids. Instead of these haploid cells, multinucleated giant cells occupied the niche of the seminiferous tubules. Immunohistochemical staining for Hsc70t, an elongating spermatid specific protein, confirmed the absence of elongating spermatids. Furthermore, RT-PCR showed that there were significantly reduced expressions of the marker genes specifically expressed in the spermatid and that there was no difference in the expressions of the spermatocyte specific marker genes. These findings indicated interruption of the spermatogenesis during transition from the spermatocyte to spermatid in the repro34/repro34 mouse. The repro34 locus has been mapped on a 7.0-Mb region of mouse chromosome 5 containing the Syntaxin 2/Epimorphin (Stx2/Epim) gene, and targeted disruption of this gene has been reported to cause defective spermatogenesis. We therefore sequenced the entire coding region of the Stx2/Epim gene and found a nucleotide substitution that results in a nonsense mutation of this gene. The expression pattern of the Stx2/Epim gene during the first wave of spermatogenesis, increased expression at later stages of spermatogenesis, was in agreement with the affected phase of spermatogenesis in the adult repro34/repro34 testis. We therefore concluded that the male infertility of the repro34/repro34 mouse is caused by the interruption of spermatogenesis during transition from the spermatocyte to spermatid and that the nonsense mutation of the Stx2/Epim gene is responsible for the interruption of spermatogenesis.     

Quantitative Evaluations of the Tubular Epithelium in the Testis of the Fallow Deer (Dama dama)

Contents: The quantitative morphology of the seminiferous epithelium was studied in 10 testes of 16- to 17-monthsold fallow bucks (Dama dama). Seminiferous tubules constitute 77.2% of the testicular parenchyma and amount to a total length of 400–750 m per testis. According to varying cell associations 6 different stages can be observed during the spermatogenic cycle. The average tubular diameter varies between 215 μm (stage 1) and 230 μm (stage 8), the epithelial height between 67.6 μm in stage 3 and 71.9 μm in stage 8 when spermiation occurs. From primary spermatocytes during the prophase of the first meiotic division preleptotenes have smallest nuclear (203.7 μm³) and cellular (469.1 μm³) volumes, whereas late diplotenes show a nuclear volume of 846.7μm³ and a cellular volume of 3440.5 μm³, that is an increase of more than 4 times for the nucleus and more than 7 times for the cell body. Numerical analysis reveals 4 spermatogonial divisions and a considerable loss of spermatogenic cells during the second meiotic division and subsequent spermiogenesis. Sertoli cells constitute between 31.4% (stage 4) and 38.3% (stage 1) of the tubular epithelium. The calculated cell volume of an individual Sertoli cell increases during every cycle from 6515.3 μm³ instage 3 to 8350.0 μm³ in stage 8; that is a volume change of 22%. The Sertoli cell organelle with most prominent cyclical variations is the endoplasmic reticulum. A lipid cycle is absent in the seminiferous epithelium of the fallow deer. Inhalt: Quantitative Studien am Keimepithel des männlichen Damwilds (Dama dama). Das Keimepithel im Hoden von fünf 16 bis 17 Monate alten Damwildjährlingen (Dama dama) wurde mit morphometrischen Methoden untersucht. Tubuli seminiferi machen 77,2% des Hodenparenchyms aus; die Gesamttubuluslange pro Hoden betragt zwischen 400 und 750 m. Sechs Spermatogenesestadien können beim Damhirsch identifiziert werden, wobei für diese Einteilung wechselnde Zellassoziationen im Keimepithel zugrunde gelegt wurden. Der Durchmesser der Tubuli seminiferi wechselt zwischen 215 μm (Phase 1)und 230 μm (Phase 8). Die Tubulusepithelhöhe schwankt ebergfalls zwischen 67,6 μm in Phase 3 und 71,9 μm in Phase 8 (Spermiation). Präleptotäne habendie kleinsten Kern- und Zellvolumina (203,7 μm³ bzw. 469,1 μm³) von allen Spermatozyten I. Ordnung, Diplotäne aus Phase 4 die größten Werte (846,7 μm³ bzw. 3440,5 μm³), das ist ein Zuwachs um das Vierfache bei mKern und um das Siebenfache beim Zeilleib. Eine numerische Anaiyse derZellzahlen in Tubulusquerschnitten aus den verschiedenen Phasen der Spermatogenese erlaubt die Schlußfolgerung, daß es 4 Spermatogonienteilungen bei dieser Spezies gibt, und daß eine beträchtliche Anzahl aller rechnerisch möglichen Keimzellen während der Spermatokenese verloren geht, vor allem während der zweiten Reifeteilung und der Spermiogenese. Sertolizellen machen zwischen 31,4 (Phase 4) und 38,3% (Phase 1) des Keimepithels aus. Eine Sertolizelle aus Phase 3 besitzt ein rechnerisches Zellvolumen von 6515,3 μm³, eine Zelle aus Phase 8 ein Zellvolumen von 8350,0 μm³. Somit verringert und vergrößert sich das Volumen der einzelnen Sertolizelle um ca. 22% in jedem Keimepithelzyklus. Das endoplasmatische Retikulum der Sertolizelle ist das Organell mit den auffälligsten zyklischen Veränderungen. Der Lipidgehalt des Keimepithels ist minimal; ein Lipidzyklus im Keimepithel, wie für andere Spezies beschrieben, existiert beim Damwild nicht.     

Immuno-histological mapping and functional association of seminal proteins in testis and excurrent ducts with sperm function in buffalo

The region-specific expression of seminal proteins in testis and excurrent duct system determines the quality and function of the spermatozoa. In the present study, localization and expression of some of the seminal proteins such as insulin-like growth factor receptor 1β (IGF-1Rβ), phosphatidylethanolamine-binding protein 4 (PEBP4), α-tubulin and tissue factor pathway inhibitor 2 (TFPI2) were carried out in testis, excurrent duct system and spermatozoa of buffalo. IGF-1Rβ was localized in the cells of the seminiferous tubules of the testis, except in primary spermatocytes. The PEBP4 was localized only in the elongated spermatid, whereas α-tubulin and TFPI2 proteins were localized in all cells of the seminiferous tubule including spermatocyte. In the buffalo spermatozoa, IGF-1Rβ, PEBP4, α-tubulin and TFPI2 were localized in the acrosome region, the post-acrosomal region till the tail end, post-acrosome to the entire tail region and the equatorial region, respectively. The study indicates that IGF-1R, α-tubulin and PEBP4 proteins regulate spermatogenesis, whereas TFPI2 may be involved during the zona binding process of the buffalo spermatozoa.     

The Annual Testicular Cycle of the Domestic Quail (Coturnix coturnix japonica)

A morphometric study was conducted on the testis of the domestic quail Coturnix coturnix japonica to determine testicular kinetics. We investigated the variability along the year of testicular parameters such as seminiferous tubule diameter, germinal epithelium height and amount of meiotic figures of maturing spermatids in the seminiferous epithelium and of sperm in the tubular lumen. The results of morphometric analysis showed the occurrence of an annual testicular cycle defined by four distinct phases: a resting phase (at the end of summer), a recrudescence phase (in the fall), a proliferative phase (at the end of winter and beginning of spring), and a regression phase (spring and summer). We also observed that the testes of adult quails present elevated and maximal spermatogenic activity in fall-winter (short-day period) and at the beginning of spring, respectively, and lower values in spring and summer (long-day periods), with minimum values at the end of summer.     

从江香猪生精上皮周期及睾丸发育的形态学分析

试验旨在探究初情期前后生精上皮周期差异及睾丸发育过程中的形态学变化。通过测定15、30、60和90 d睾丸相关指数，结合睾丸组织形态学特征，判断香猪初情期，划分从江香猪生精上皮周期。结果显示，30 d的睾丸指数较15 d极显著升高（P<0.01），睾丸重、长轴及短轴的增长率分别为298.05%、66.42%和65.45%，60和90 d两个阶段睾丸重增长率相对稳定。形态学观察表明，从江香猪30 d时生精小管出现游离精子，完成第一次生精并进入初情期；与15 d相比，30 d生精小管面积和生精上皮厚度极显著增加（P<0.01），增长率分别为136.12%和40.19%，在60和90 d均处于稳定增长状态。睾丸细胞数统计显示，日龄增加不影响支持细胞（setoli cells，SC）数量（P>0.05），而30 d生殖细胞数（germ cells，GC）较15 d极显著增加（P<0.01）。相关分析结果发现，生殖细胞数量增加与生精小管面积增大、生精上皮厚度变化之间呈明显正相关（r=0.994；0.96）。根据生殖细胞组合形式差异，将初情期前后生精上皮分为3和8个阶段。初情期前生殖细胞以第一次减数分裂前期为主，A、B型精原细胞、SC、初级精母细胞（primary spermatocyte，Ps）、前细线期（preleptotene，PI）、细线期（leptotene，L）等生殖细胞在初情期前后生精上皮中均存在，而圆形精子（round spermatids，R）、延伸精子（elongating spermatid，E）、精子细胞（spermatozoa，S）仅存在于初情期后的生精上皮。本研究结果表明，从江香猪30 d初情，睾丸发育以生殖细胞和生精小管面积的迅速增加为主，该结果对从江香猪早熟性状挖掘、种猪选育及开发利用等有重要的指导意义。     

Testis Morphometry and Stages of the Seminiferous Epithelium Cycle in an Epididymal Sperm‐storing Neotropical Vespertilionid,Myotis levis (Chiroptera)

Yellowish myotis, Myotis levis, is a seasonal, epididymal sperm‐storing Neotropical vespertilionid. In the dry season, males show simultaneous testis regression and sperm storage in cauda epididymis, enabling them to mate during this season. In this study, we investigated seasonal variations in body mass, diameter and height of seminiferous tubules and nuclei of Leydig cells in a population of southeastern Brazil. We also determined the frequencies of the stages of the seminiferous epithelium cycle (SEC) of mature individuals of this population. Body mass and diameter of Leydig cell nuclei showed no significant differences between dry and rainy seasons and stages of annual reproductive cycle; however, all other morphometric parameters varied significantly. The relative cumulative frequency of pre‐meiotic stages of the SEC (1–3) was 51%, of meiotic stage (4) was 2% and of post‐meiotic stages (5–8) was 47%. We confirmed that the yellowish myotis presents seasonal sperm production as revealed by testis regression and epididymal sperm storage during the dry season.