Histomorphometric evaluation of the neotropical brown brocket deer Mazama gouazoubira testis, with an emphasis on cell population indexes of spermatogenic yield

Testicular histomorphometric patterns and spermatogenesis dynamics of Oecomys bicolor tomes, 1860 (Rodentia: Cricetidae)

Although the order Rodentia does not present a high risk of extinction compared to mammals as a whole, several families demonstrate high levels of threat and/or data deficiency, therefore highlighting the need for targeted research and the application of ecological and reproductive data to the development of conservation actions. The order Rodentia, the largest among mammals, includes 9 families, and the family Cricetidae is the most diverse of the Brazilian rodents. In Brazil, 12 of the 16 genera of Oecomys are found. Oecomys bicolor is known in Brazil as the 'arboreal rat' and is, found in dry, deciduous and tropical forests. The mean body weight of Oecomys bicolor was 35.8 g and the gonadal, tubular and epithelial somatic indexes were, 0.53%, 0.47% and 0.37%, respectively. Seminiferous tubules volume density was 89.72% and the mitotic and meiotic indexes corresponded to 8.59 and 2.45 cells, respectively, and the yield of spermatogenesis was 23.83 cells. The intertubular compartment represented 10.28% of the testis parenchyma and around 5% of the interstitial space was occupied by Leydig cells, whose number per gram of testis was 11.10 × 107 cells. By evaluating the biometric and histomorphometric characteristics of the testis, there is evidence that this species has a high investment in reproduction. Due to the high contribution of the seminiferous epithelium and the intertubular compartment in this species, compared to the others of the same family, it is possible to infer that the species Oecomys bicolor has a promiscuous reproductive behaviour.

Identification and Determination of the Seminiferous Epithelium Stages and Spermatid Development in the Testis of Aceh Bull (Bos indicus)

This study was conducted to describe the stages of seminiferous epithelium (SE), determine the relative frequency of the stages, and identify the steps of spermatid development during spermatogenesis in the testicular tissue of Aceh bull. Seven pairs of the testicular organs of Aceh bull (Bos indicus) were used and then processed in a histological manner for staining using haematoxylin and eosin (H&E) and periodic acid-Schiff-haematoxylin (PAS-H). The stages of seminiferous tubules were examined using a tubular morphology method while spermatid development was observed based on the acrosome formation during spermatid development. Eight stages (stages I to VIII) of SE were found in the testicular seminiferous tubules of Aceh bull. Furthermore, the percentage of the relative frequency of each stage was 25.48, 15.38, 12.92, 4.74, 14.97, 10.69, 10.74, and 5.08%, respectively, with the relative frequency of premeiotic, meiotic, and postmeiotic phases being 53.78, 4.74, and 41.48%, respectively. Spermatid development from round to elongated spermatids occurred in 14 steps. Steps 1 to 7 were observed in stage I, steps 8 and 9 in stage II, steps 10 and 11 in stage III, step 12 in stage IV, step 13 in stages V and VI, and step 14 in stages VII and VIII. These findings can be used as a basis for further studies, particularly in evaluating the abnormality of the cellular composition of the seminiferous tubule in each stage of spermatogenesis and also in determining daily sperm production in Aceh bull.

Intertubular morphometric and ultrastructural testes analyses in mdx mice

Duchenne Muscular Dystrophy (DMD) reproductive alterations and the influence of antioxidant treatments may aid in understanding morphometry testicular quantification. In this context, the aim of the present study was to characterize the intertubular compartment (ITC) morphometry of animal testes in mdx mice supplemented with ascorbic acid (AA). Sixteen mice were used, namely the C57BL/10 (non-dystrophic) and C57BL/10Mdx (dystrophic) lineages, distributed into the following groups: Control (C60), Dystrophic (D60), Control supplemented with AA (CS60), Dystrophic supplemented with AA (DS60). A total of 200 mg/kg of AA were administered to mice for 30 days. Subsequently, the testicles were collected, weighed, and fragmented. The obtained fragments were fixed in Karnovsky's solution (pH 7.2) and embedded in historesin for morphometric and transmission electron microscopy assessments. Leydig cells were hypertrophic in the D60 group, but was reverted by AA supplementation in the DS60 group. The DS60 group also exhibited increased intertubular volume compared to the CS60 group. The ultrastructural images identified multilamellar bodies in dystrophic animals (lipid storage) and telocyte cells (transport substances) in both control and dystrophic animals. Morphometric alterations were, therefore, noted in the intertubular compartment due to Duchenne muscular dystrophy (DMD), with AA administration capable of altering Leydig cells in this condition.

Histomorphometric changes of testicular tissues by season and age of Algerian local donkeys (Equus asinus)

The present investigation was undertaken to highlight the histomorphometric changes of testicular tissues according to season and age in donkeys (Equus asinus) under northern Algeria conditions. The experiment was conducted from February 2019 to January 2020. A total of 21 sexually mature donkeys were selected randomly. The testis were immediately collected after slaughter for the histological observation. The analysis of the correlation coefficients shows negative correlations between DL and other parameters such as DST, GCEH, TTA and ITSA, ranged between -0.24 and -0.79. Also, there were a high negative correlations between season and the histomorphometric parameters, except DL was revealed positive (r=0.65). On the other hand, there were positive correlations between age and testicular histomorphometrics parameters. The results indicated that DST, GCEH, TTA and ITSA values were significantly higher in winter and autumn seasons than in spring and summer seasons. It is also noteworthy that DST, GCEH, TTA and ITSA values were significantly higher in adult and aged donkeys than in young donkeys. Our comparative analysis of histological parameters, suggests that the sexual activity usually occurs during winter and autumn in local donkeys of Algeria. In addition, our results of histomorphometric of testicular tissues are correlated with age of donkeys.

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.

Assisted Reproductive Technology in Neotropical Deer: A Model Approach to Preserving Genetic Diversity

Simple Summary

Deer species in the Neotropical region have undergone a decline of their populations. Although conservation of their natural habitat is considered the best way to assist the species, the speed of occupation of these areas and the anthropic actions are so fast that the efforts are, at times, insufficient. As free-living populations decrease, there is a descent in the genetic diversity and an increase in crossbreeding between related individuals (inbreeding). Genetic diversity is essential for survival, since it enables natural selection to occur, providing adaptation and maintenance of the species. To protect the genetic diversity, it is possible to use reproductive techniques and conserve different types of cells, which can be used in the future to reestablish any alleles that have been lost by the populations.

Abstract

One of the most significant challenges in deer is the ability to maintain genetic diversity, avoiding inbreeding and sustaining population health and reproduction. Although our general knowledge of reproductive physiology is improving, it appears that the application of assisted reproductive technology (ART) will more efficiently advance wildlife conservation efforts and preserve genetic diversity. The purpose of this review is to present the most important results obtained with the use of ART in Neotropical deer. Thus, the state-of-the-art for estrus synchronization, semen technology, artificial insemination, and in vivo embryo production will be presented. In vitro embryo production (IVP) is also a biotechnology that is taking initial steps in deer. In this aspect, the approach with the proteomics of ovarian follicular fluid is being used as a tool for a better understanding of oocyte maturation. Finally, cell banks and the use of interspecific somatic cell nuclear transfer (iSCNT) as well as the use of stem cells for gametes differentiation are promising techniques.

Seasonal evaluation of spermatogenesis of the hematophagous bat Desmodus rotundus in the Caatinga biome

This study was aimed to characterize the spermatogenic process and its seasonal variation in Desmodus rotundus, in the Caatinga biome, a water-limited ecosystem, with marked water restriction during most of the year. Collections of adult animals were performed during the dry and rainy seasons, and after euthanasia, their testes were processed histologically to perform morphological, morphometric, ultrastructural and immunohistochemical analyzes. The percentage of seminiferous epithelium, number of Leydig cells per gram of testis, and population of Sertoli cells and A-type spermatogonia presented by D. rotundus were significantly higher in the rainy season, while the percentage of lumen, mitotic index, support capacity performed by Sertoli cells, and overall yield of spermatogenesis were higher in the dry season. The ultrastructure of spermatogenesis was similar to that described in other mammals, and the immunohistochemical analysis revealed activity of the aromatase enzyme in Sertoli cells, Leydig cells, spermatocytes and spermatids, as well as the presence of androgen receptors in Sertoli cells and Leydig cells. FGF2 activity was detected in primary spermatocytes in zygotene and pachytene, as well as secondary spermatocytes and rounded and elongated spermatids, while the BCL-2 protein was expressed in primary spermatocytes in zygotene and pachytene, secondary spermatocytes, and rounded spermatids. The activity of these molecules was similar in both seasons, and associated with the morphometric findings, indicates maintenance in the integrity of the seminiferous epithelium throughout the year. The seasonal study of D. rotundus spermatogenesis indicates a continuous spermatogenesis pattern and suggests a greater production of spermatozoa in the rainy season in the Caatinga biome.

Characterization of seminal parameters, sperm morphometry, micromorphology, and ultrastructure in gray brocket deer (Mazama gouazoubira, Fischer, 1814)

Populations of gray brocket deer (Mazama gouazoubira) are declining; yet, knowledge on the reproductive biology of this species remains limited. Therefore, this study aimed to describe morphology, viability, membrane integrity, mitochondrial activity, morphometry, micromorphology, and ultrastructure of the gray brocket deer sperm. Three adult male gray brocket deer were used in the study. Semen collection was performed using electroejaculation. Semen were analyzed by evaluating pH, motilities, vigor, mass movement, volume, concentration, viability, membrane integrity, mitochondrial activity, morphology, and morphometry. Micromorphology and ultrastructure of sperm were analyzed using scanning and transmission electron microscopy (SEM and TEM), respectively. There was no significant difference among males regarding on pH, motilities, vigor, mass movement, volume, concentration, viability. High values for membrane integrity, mitochondrial activity, and normal sperm were observed. The most frequent defects were simple bent tail and bowed midpiece. The head length, and width, midpiece, and tail length were 8.5, 4.4, 11.5, and 41.3 μm, respectively. SEM sperm showed paddle-shaped heads, with apical ridge and serrated band on the equatorial segment. TEM revealed the nucleus, acrosome, plasma membrane, mitochondria sheath, proximal centrioles, segmented columns, axoneme, outer dense fibers, and fibrous sheath. SEM and TEM showed the presence of some abnormalities. These results are expected to provide baseline values of diverse semen parameters, contributing toward the development of reproductive biotechnologies for gray brocket deer and, other deer species at risk of extinction.

Synergic effects of aerobic exercise and eugenol supplement on germ cell development and testicular tissue structure in chlorpyrifos-treated animal model

Insecticide chlorpyrifos (CPF) with increased oxidative stress, structural destruction, and hemostasis of testicular tissue leads to male infertility. The present study investigated the protective effect of exercise (Exe) and eugenol supplementation (Sup) on CPF-induced testicular spermatogenic disorders in male rats. In this experimental study, 21 adult male albino rats were divided into seven groups, control (Co: 6 weeks), CPF (6 weeks), Co + Oil (2 weeks healthy food and 4 weeks oil), Co + Dimethylsulfoxide (DMSO: 6 weeks), CPF + Sup (2 weeks CPF and 4 weeks CPF + Sup), CPF + Exe (2 weeks CPF and 4 weeks CPF + Exe), and CPF + Exe + Sup (2 weeks CPF and 4 weeks CPF + Exe + Sup) group. All treatments were done intraperitoneally (5 days a week). Exe groups were subjected to run at moderate exercise intensity for 5 days per week over 6 weeks. DMSO groups were administered to the equal volume of vehicle for 6 consecutive weeks. Finally, the animals were sacrificed with Co2 gas and then alterations in testicular histology and sperm parameters were evaluated. Protein expression of PLZF and IGFα in the CPF group showed a significant decrease compared with the control group (p ˂ 0.001 for both). It was shown that CPF + Exe + Sup (p ˂ 0.001) and CPF + Sup (p ˂ 0.01) groups had a significant increase in protein expression of PLZF, but the protein expression of IGFα showed a significant increase just in the CPF + Exe + Sup group (p ˂ 0.001). Also, CPF caused a significant decrease in Leydig counts, Sertoli cell count, spermatogonium counts, spermatocyte cell count, spermatid cell count, and tunica thickness as well as a significant increase in testicle diameter (p ˂ 0.01) and ducts diameter compared with the control group. It seems that aerobic exercise with eugenol supplementation suppresses the disruption effects of CPF on testicular tissue (cellular and structural) by increasing the antioxidant capacity and improving the secretion of sex hormones. Therefore, the aerobic exercise with supplement of the eugenol has potential therapeutic targets for male infertility that need further study.

Duration of the seminiferous epithelium cycle in the frugivorous bat Artibeus lituratus

The seminiferous epithelium goes through multiple changes which enables the differentiation of a spermatogonia in a fully mature spermatozoon. The timing of these changes is species-specific and influences the duration of the reproductive cycles. Bats are among wild mammals whose coordination between male and female reproductive cycles are imperative, since most females show seasonal preferences, even in the Tropics. This seasonal variation demands constant sperm production ready for spermiation in order to guarantee its genetic dispersion and reproduction success. Despite their abundance, little is known about the duration of reproductive cycles in Neotropical bat species, a relevant information for the species management and for conservational strategies regarding anthropogenic and climate influences on bats reproduction. In this study, we aimed at characterizing the stages of the seminiferous epithelium cycle (SEC) of the fruit bat Artibeus lituratus and to determine its duration based on the immunohistochemical analysis of the bromodeoxyuridine (BrDU) activity. SEC stages were characterized according to the tubular morphology method and the frequency of each stage was estimated. After intratesticular injections of BrDU, the animals were euthanized at different times, and the estimation of SEC duration was performed by observing the most advanced germ cells in the seminiferous epithelium. The most advanced stained cells after 2 days of BrdU injection were the primary spermatocytes in pachytene, transitioning from stages 1-2 of the SEC. Within 2 days, we found a progression of 30.42% of the SEC, and an entire cycle lasted 6.58 days on average. Considering that 4.5 seminiferous epithelium cycles are necessary for the whole spermatogenic processes to be completed, the total length of spermatogenesis in A. lituratus was estimated at 29.61 days. Our findings support a pattern of bimodal seasonal polyestry for this species, with rapid spermatogenic cycles.

Testicular characterization and spermatogenesis of the hematophagous bat Diphylla ecaudata

Diphylla ecaudata is a hematophagous bat endemic of South America, with food preference for bird blood. Given the lack of information about the reproductive activity of this species, this study aimed to describe the testicular morphology and histomorphometry of D. ecaudata in order to understand its reproductive biology, specially spermatogenesis. The animals were collected in Lajes city, Rio Grande do Norte, Brazil. Following euthanasia, the testes were histologically processed for morphological, morphometric, ultrastructural and immunohistochemical analyses. Their average body weight was 24.64g, with a gonadosomatic index of 0.49%, tubulesomatic index of 0.47%, and a total of 32.20m of seminiferous tubules per gram of testis. The pre-meiotic, meiotic, and post-meiotic phases accounted for 56.20%, 9.30%, and 34.50% of the seminiferous epithelium cycle, respectively. The ultrastructure of spermiogenesis was similar to that described in other mammals and the perforatorium was not observed in the sperm. Androgen receptors were detected in Sertoli cell nuclei and Leydig cell cytoplasm, while aromatase enzyme was detected only in Sertoli cell nuclei. FGF2 and BCL-2 activities were detected in the cytoplasm of zygotene and pachytene primary spermatocytes, as well as round and elongated spermatids. D. ecaudata showed testicular pattern similar to other mammals and characteristics common to other bat species. This species stood out for its high efficiency of Sertoli cells, which presented high capacity to support germ cells, besides the highest sperm production rates among those already recorded. This study is the first step towards the knowledge of D. ecaudata reproduction and the first description of its spermatogenesis.

Reproductive functions in Desmodus rotundus: A comparison between seasons in a morphological context

Reproductive seasonality in Neotropical bats has been assessed to the better understand their reproductive behavior. This knowledge is especially important for the control of Desmodus rotundus population as it is a transmitter of rabies virus. Therefore, we aimed to evaluate the functional activity of testis and epididymis of D. rotundus in dry and rainy seasons under a morphological approach. We observed an increase in tubular diameter and epithelial height of the seminiferous tubules during the rainy season. In the latter, additionally, stereological analysis of the testis showed increased proportion of seminiferous epithelium and reduced percentage of lumen. The sperm number in caput/corpus epididymis increased in rainy season, whereas sperm count and transit time were reduced in cauda region. These alterations were probably related to the recovery of epithelium activities after mating season in dry season. Despite altered nuclear and cytoplasm parameters of Leydig cells between seasons, the volume and number of these cells were constant. Moreover, no change in serum testosterone levels, daily sperm production, and apoptotic index were observed, which indicates that the reproductive pattern in D. rotundus does not change between seasons. Our study offers a baseline for the management of vampire bat population as an attempt to control rabies disease.

Characterization of Seminiferous Epithelium Stages in the Wild Javan Muntjac (Muntiacus muntjak muntjak) Using the Tubular Morphology Method

Stages of the seminiferous epithelium of the testis of the wild Javan muntjac (Muntiacus muntjak muntjak) in hard antler period were characterized based on the tubular morphology method. The number and the relative frequencies of seminiferous epithelium stages and the morphometry of germinal cell nuclei were identified microscopically. We identified eight stages of seminiferous epithelium in testicular tissue of the Javan muntjac and found that the relative frequencies of stages I to VIII were 14.87, 15.12, 17.75, 6.87, 7.37, 12.37, 13, and 12.62%, respectively. The diameter of the nuclei of germinal cells varied in each stage of seminiferous epithelium. Diplotene-stage primary spermatocytes had prominent and large nuclei ~8.97 ± 1.0 μm in stages III and IV. Pachytene primary spermatocytes appeared in most stages, except stage IV, whereas leptotene- and diplotene-stage primary spermatocytes were found in stages I and II, and III and IV, respectively. Round spermatids were observed in stages IV to VIII and in stage I but were absent in stages II and III, while elongated spermatids were observed in all stages except stage I. Our findings show that the stages of seminiferous epithelium in the Javan muntjac are similar to those found in neotropical cervids, small ruminants, and other domestic animals.

Asymmetrical size and functionality of the pampas deer (Ozotoceros bezoarticus) testes: Right testis is bigger but left testis is more efficient in spermatogenesis

Information about gonadal asymmetries in ruminants is very scarce. In this work, we performed three complementary studies to compare characteristics of both testes: (i) weight and size of offspring and adult dead males; (ii) the tissue:fluid relationship determined by ultrasound scanning; and (iii) the spermatogenic status using fine needle aspiration cytology. The right testis was heavier than the left one in both offspring and adult animals and had greater width and volume in adult males than the left one. The ultrasound pixel intensity was similar in both testes. The right testis tended to have more spermatogonia (p = .06) and had a greater percentage of early spermatids (p = .004) than the left testis. On the other hand, the left testis had a greater percentage of spermatozoa (p = .05). The left testis had a greater spermatozoa/spermatogonia ratio (p = .02) and tended to have more spermatozoa/Sertoli cells ratio (p = .07). The spermatogenic index tended to be greater in the left than in the right testis (p = .06). Overall, we concluded that the right testis of pampas deer males is bigger but according to the cytology, it seems to be less spermatogenically effective than the left one, but these differences are not explained by different tissue:fluid ratio in each testis. Although differences were greater in adults than in offspring, asymmetry was observed even in just born offspring.

The spermatogenic process of the common vampire bat Desmodus rotundus under a histomorphometric view

Among all bat species, Desmodus rotundus stands out as one of the most intriguing due to its exclusively haematophagous feeding habits. However, little is known about their spermatogenic cycle. This study aimed at describing the spermatogenic process of common vampire bats through testicular histomorphometric characterization of adult specimens, spermatogenic production indexes, description of stages of the seminiferous epithelium cycle and estimative of the spermatogenic process duration. Morphometrical and immunohistochemical analyzes for bromodeoxiuridine were conducted under light microscopy and ultrastructural analyzes were performed under transmission electron microscopy. Vampire bats showed higher investment in gonadal tissue (gonadosomatic index of 0.54%) and in seminiferous tubules (tubulesomatic index of 0.49%) when compared to larger mammals. They also showed a high tubular length per gram of testis (34.70 m). Approximately half of the intertubular compartment was found to be comprised by Leydig cells (51.20%), and an average of 23.77x10⁶ of these cells was found per gram of testis. The germline cells showed 16.93% of mitotic index and 2.51% of meiotic index. The overall yield of spermatogenesis was 60% and the testicular spermatic reserve was 71.44x10⁷ spermatozoa per gram of testis. With a total spermatogenesis duration estimated at 37.02 days, vampire bats showed a daily sperm production of 86.80x10⁶ gametes per gram of testis. These findings demonstrate a high sperm production, which is commonly observed in species with promiscuous mating system.

Could vitamin C and zinc chloride protect the germ cells against sodium arsenite?

Arsenic (As) is commonly associated with natural and human processes such as volcanic emissions, mining and herbicides production, being an important pollutant. Several studies have associated As intake with male fertility reduction, thus the aim of the present study was to evaluate whether vitamin C and/or zinc would counteract As side effects within the testicles. Adult male Wistar rats were divided into six experimental groups: control, sodium arsenite (5 mg/kg/day), vitamin C (100 mg/kg/day), zinc chloride (ZnCl2; 20 mg/kg/day), sodium arsenite + vitamin C and sodium arsenite + ZnCl2. Testicles and epididymis were harvested and either frozen or routinely processed to be embedded in glycol methacrylate resin. As reduced the seminiferous epithelium and tubules diameter due to germ cell loss. In addition, both the round spermatids population and the daily sperm production were reduced. However, ZnCl2 and vitamin C showed to be effective against such side effects, mainly regarding to sperm morphology. Long-term As intake increased the proportions of abnormal sperm, whereas the concomitant intake of As with zinc or vitamin C enhanced the proportions of normal sperm, showing that such compounds could be used to protect this cell type against morphological defects.

Influência da estação do ano sobre a estrutura testicular em ovinos explorados no sul do Estado do Piauí

RESUMO: Objetivou-se avaliar a influência da estação do ano sobre a estrutura testicular de ovinos SRD. Foram utilizados 10 animais com idade entre dois e três anos. Os testículos foram seccionados e fixados em solução de Bouin por 24h. Os fragmentos foram submetidos ao processamento histológico, emblocados em parafina e corados com hematoxilina eosina. Foram avaliadas a proporção volumétrica dos compartimentos testiculares, o diâmetro dos túbulos seminíferos, altura do epitélio seminífero e frequências dos estágios do ciclo do epitélio seminíferos. Os dados foram submetidos à análise de variância a 5% de probabilidade, do programa estatístico SAS 9.0. Os resultados revelaram todos os valores pesquisados sofreram influência da estação do ano. O valor do diâmetro tubular foi de 143,98±17,83 e 170,37±26,64μm, a altura do epitélio seminífero foi de 44,92±9,23 e 50,06±13,61μm e a proporção volumétrica foi de 78,32±13,68 e 80,13±15,14% nos períodos seco e chuvoso, respectivamente. A quantificação das células germinativas e de Sertoli mostrou todos os valores foram maiores no período chuvoso quando comparados com o seco. Concluiu-se que a estação do ano interferiu na estrutura testicular, tendo em vista que todos os valores da proporção volumétrica dos componentes testiculares mostraram diferença significativa entre as estações do ano, pois os valores foram mais acentuados no período chuvoso.

Evaluation of the cell population of the seminiferous epithelium and spermatic indexes of the bat Sturnira lilium (Chiroptera: Phyllostomidae)

Due to the scarcity of information about patterns of spermatogenesis in bats, this study aimed to provide information on the testicular activity of the bat Sturnira lilium along the annual seasons. Thus, a series of morphometrical and stereological analyses were made using the testes of adult S. lilium in order to achieve a better understanding of the sperm production dynamics. Light and transmission electron microscopy analyses were performed in testicular fragments of animals captured during dry and rainy seasons. The testes followed the pattern of organization described for other mammals, and there were no morphological differences between organs collected either in dry or in rainy seasons. Each tubular cross-section in stage 1 was made of 0.5 type-A spermatogonia, 4.4 primary spermatocytes in preleptotene/leptotene, 3.7 in zygotene, 11.9 in pachytene, 35.6 round spermatids and 8.5 Sertoli cells. The mitotic and meiotic indexes were 15.4 and 2.9 cells, respectively, while the spermatogenesis yield was 68.7 cells. The testicular sperm reserves was 37.61×10⁶ cells, and daily sperm production per gram of testis averaged 209.68×10⁶ cells, both highest averages occurring in the rainy season. S. lilium male bats have a continuous reproductive pattern, high spermatogenesis yield and low support capacity by the Sertoli cells.

The tubular compartment and the spermatogenic dynamics of the wild rodent Oxymycterus nasutus (Rodentia: Cricetidae)

Despite the order Rodentia present worldwide distribution and large number of species in the Brazilian fauna, detailed studies on testicular morphophysiology are still scarce. Therefore, this study aimed to analyze the dynamics of the spermatogenic process of Oxymycterus nasutus using morphometrical and stereological tools. Testicles from ten sexually mature males were used, showing a gonadosomatic index of 0.89%. The testicular parenchyma showed one of the highest tubulesomatic indexes reported among wild rodents - 0.82% - from which 65.12% was allocated into seminiferous epithelium. The average tubular diameter was 249.89 μm, whereas the epithelium height was 62.47 μm and the total length was 18.62 m per gram of testis. Eight different stages of the seminiferous epithelium cycle were described. Stage 1 was used for counting the germ cell population as well as the Sertoli cells. On average, 3.47 type-A spermatogonia, 24.39 primary spermatocytes in preleptotene/leptotene, 24.13 primary spermatocytes in pachytene, 68.38 round spermatids and 7.33 Sertoli cells were found per tubular cross section. There were 91.02 × 10(6) Sertoli cells per gram of testis and each cell was able to support 9.33 spermatids and 16.43 germ cells. The coefficient of spermatogonial mitosis was 7.02, while 2.83 spermatids were produced for each primary spermatocyte in pachytene. The overall efficiency of spermatogenesis was 19.70 cells, whereas the sperm reserve per gram of testis totalized 849.63 × 10(6) spermatids. Therefore, the presented data showed that O. nasutus shows a high energetic investment in reproduction, corroborating the findings for other species of the Cricetidae family.

Seasonal variation of energy reserves and reproduction in neotropical free-tailed bats Molossus molossus (Chiroptera: Molossidae)

Seasonal variation is a key factor regulating energy metabolism and reproduction in several mammals, including bats. This study aimed to track seasonal changes in the energy reserves of the insectivorous bat Molossus molossus associated with its reproductive cycle. Adult males were collected during the four neotropical annual seasons in Viçosa - MG, Brazil. Blood and tissues were collected for metabolic analysis and testes were removed for histology and morphometry. Our results show that liver and breast muscle glycogen concentrations were significantly lower in winter. The adiposity index was significantly higher in the fall compared to winter and spring. Seminiferous tubules were greater in diameter in animals captured in fall and winter, indicating a higher investment in spermatic production during these seasons. The percentage of Leydig cells was higher in summer compared to fall and winter. We suggest that M. molossus presents a type of seasonal reproduction with two peaks of testicular activity: one in fall, with higher sperm production (spermatogenesis), and another in summer, with higher hormone production (steroidogenesis). The metabolic pattern may be associated with reproductive events, especially due to the highest fat storage observed in the fall, which coincides with the further development of the seminiferous tubules.

Stages and duration of the seminiferous epithelium cycle in the bat Sturnira lilium

Knowledge of the stages that compose the seminiferous epithelium cycle (SEC) and determination of the duration of spermatogenic processes are fundamental for the accurate quantification of the dynamics of spermatogenesis. The aim of this study was to characterize the stages that compose the SEC of the bat Sturnira lilium, including evaluation of the average frequency of each of these stages throughout the year and calculation of the duration of the spermatogenic process. An ultrastructural characterization of the formation of the acrosomal cap was also performed. Testicular fragments were processed for morphological and immunohistochemical analysis as well as ultrastructural analysis using transmission electron microscopy. According to the tubular morphology method, the SEC in S. lilium is divided into eight stages, following the pattern found in other mammals. Primary spermatocytes were found at zygotene in stage 1 of the cycle. There was no variation in frequency of each of the stages over the seasons, with stage 1 being the most frequent, and stage 7 the least frequent. The duration of one seminiferous epithelium cycle was 3.45 days, and approximately 15.52 days were required for the development of sperm from spermatogonia. Ultrastructural characterization allowed the formation of the acrosomal cap in round spermatids to be monitored. In conclusion, the stages that compose the SEC in S. lilium are generally similar to those described for other mammals, but the duration of the spermatogenic process is shorter than previously recorded for mammals. The presence of primary spermatocytes at zygotene in stage 1 of the cycle is probably due to the longer duration of this stage.