The hormonal control of the uterus of the bat Myotis nigricans during its different reproductive phases: emphasis on progesterone and estradiol.

Myotis nigricans is a species of bat from the Vespertilionidae family that is endemic of the Neotropical region. Its insectivorous feeding habit plus its large range of prey species, great geographical dispersion, wide colonies, and anthropomorphized behavior make this species an important ecological agent that acts in the control of nocturnal insects. Reproductively, M. nigricans presents geographic variations, having different patterns of reproduction according to its geographical location. Despite these extremely interesting characteristics, no more detailed study of the hormonal control of the reproduction of this species has been conducted. Therefore, the aim of the present study was to evaluate the variations in serum hormone concentrations and in uterine hormonal control of this bat during its different reproductive phases. Twenty adult females were collected, divided into four (4) sample groups, according to the reproductive status (nonreproductive, initial, and advanced pregnancy and lactating), and submitted to hormone dosage and immunohistochemical analyses. The results demonstrated that the uterus of M. nigricans is strongly regulated by the interaction/cross-talk between serum concentrations of estradiol (E2) and progesterone with their respective hormone receptors. Significant increases in the concentration of E2 and progesterone are needed to regulate the early pregnancy. The persistence of the corpus luteum throughout pregnancy is necessary, since its placenta does not express aromatase. The expressions of ERα and PR appear to be synchronized in order to coordinate a large portion of the processes that occur inside the uterus of M. nigricans during pregnancy and lactation.

Alphacoronavirus Detection in Lungs, Liver, and Intestines of Bats from Brazil.

Bats are flying mammals distributed worldwide known to host several types of Coronavirus (CoV). Since they were reported as the probable source of spillover of highly pathogenic CoV into the human population, investigating the circulation of this virus in bats around the world became of great importance. We analyzed samples from 103 bats from two distinct regions in Brazil. Coronavirus from the Alphacoronavirus genus was detected in 12 animals, 11 from São José do Rio Preto-SP region and 1 from Barreiras-BA region, resulting in a prevalence of 17.18% and 2.56% respectively. The virus was detected not only in intestines but also in lungs and liver. Phylogenetic analysis based on nsP12 genomic region suggests that the sequences group according to host family and sampling location. Studies on the circulation of these viruses in bats remain important to understand the ecology and evolutionary relationship of these pathogens.

Structure, histochemistry and seasonal variations of the male reproductive accessory glands in the Pallas's mastiff bat, Molossus molossus (Chiroptera: Molossidae).

Due to their wide geographical distribution, bats suffer considerable influence from abiotic factors on their reproductive strategies, detected through behavioural or functional assessment of the gonads and accessory glands. The present study aimed to characterise anatomically and morphologically the reproductive accessory glands (RAGs) of Molossus molossus (Molossidae) and evaluate their seasonal variations. The RAGs were removed, fixed, sectioned after histological processing and submitted to the following stains: haematoxylin-eosin, periodic acid--Schiff (PAS) and Gömöri's reticulin. Our data demonstrated that the RAGs of M. molossus are composed of a semi-lobed prostatic complex associated with the urethra and a pair of inguinal bulbourethral glands. Histology and three-dimensional reconstruction of the prostatic complex demonstrated the existence of two regions: ventral and dorsal (named according to the position around the urethra). The two regions had distinctive morphological and histological differences, with the ventral region being the most prominent and the dorsal formed by four lobes. Considering the seasonal evaluation, we can infer that the prostatic complex of M. molossus is active throughout the seasons in São Paulo State (Brazil) and, although each of the prostatic regions has inherent characteristics, they synchronise to establish the main reproductive peak in spring (early rainy season).

Two periods of total testicular regression are peculiar events of the annual reproductive cycle of the black Myotis bat, Myotis nigricans (Chiroptera: Vespertilionidae).

Myotis nigricans presents few and controversial reproductive data, which indicate geographical variation in reproduction. Thus, this study aimed to evaluate the seasonal modifications in testicular and epididymal morphologies in a tropical environment, submitting these organs to morphometric and immunohistochemical analysis. The observations revealed that this species presents two peaks of spermatogenic activity followed by two periods of total testicular regression (a quiescent pre-pubertal-like morphology, where only Sertoli cells and spermatogonia could be observed), in the same annual reproductive cycle, which seem to be only indirectly influenced by abiotic factors. This testicular behaviour seems to be synchronised with the caput and corpus epididymidis, but not with the cauda epididymidis, which presents aspects of sperm storage in May-June. The control of this variation seems to be directly linked to the expression of the androgen receptor, since, throughout the year, it is high in periods of testicular recrudescence and low in periods of deactivation. It is not thought to be directly linked to apoptosis, which is more pronounced in periods of recrudescence than in periods of regression.

Structure, histochemistry, ultrastructure and seasonal variations of the male prostatic complex in the black Myotis bat, Myotis nigricans (Chiroptera: Vespertilionidae).

Chiroptera are one of the most diverse orders of mammals and a unique group within Mammalia that posses a wide geographic distribution and considerable variability in reproductive strategies. The aims of the present study were to characterise the male prostatic complex of the bat Myotis nigricans (Vespertilionidae) and evaluate seasonal variations in the prostatic complex of M. nigricans specifically. Twenty-three sexually mature specimens (four sample groups: winter, spring, summer and autumn) were subjected to macroscopic, microscopic, morphometric and ultrastructural analyses. The reproductive accessory glands of M. nigricans were found to be composed of a multilobed complex associated with the urethra and a pair of inguinal bulbourethral glands. The complex was composed of three bilobed prostatic regions (ventral, dorsolateral and dorsal) with no ampullary gland and seminal vesicles. This pattern of lobulation is very similar to that described for the prostate of rodents; however, it differs from that of other mammals and even other families of bats (e.g. Phyllostomidae and Molossidae). Each prostatic region in M. nigricans has unique and distinctive characteristics, which synchronise to establish the main reproductive peak of the species in summer. The data also indicated an asynchrony in the activity of primary and secondary reproductive organs in the annual reproductive cycle of M. nigricans in São Paulo State, Brazil.

Differential expression of aromatase, estrogen receptor alpha and 17ß-HSD associated with the processes of total testicular regression and recrudescence in the bat Myotis nigricans (Chiroptera: Vespertilionidae).

Despite the worldwide distribution and many unique reproductive adaptations that bats present, many aspects of their reproductive hormonal regulation have not been adequately studied, especially in species that presented patterns of total testicular regression. Thus, this study aimed to evaluate the testicular expression of 17ß-HSD type 1, aromatase and ERα in the bat Myotis nigricans, during the four periods of its reproductive cycle. Immunoreactivity for ERα was detected only in the cytoplasm of elongated spermatids and in the nuclei of spermatogonia and Sertoli cells. Expression of aromatase was observed in round and elongated spermatids and in Sertoli and Leydig cells. Immunoreactivity for 17ß-HSD was restricted to the cytoplasm of Leydig cells. The three expression patterns varied significantly during the four periods of the reproductive cycle. Expression of ERα and aromatase in spermatids was continuous, while expression of ERα in spermatogonia occurred only in initial types (Ap). Expression of ERα and aromatase in Sertoli cells varied, with expression only in periods of spermatogenetic activities; and the same variation was observed for the expression of aromatase and 17ß-HSD in Leydig cells. We, therefore, propose that the processes of total testicular regression and posterior recrudescence suffered by M. nigricans from September to January in the northwest of the São Paulo State of Brazil, are directly regulated by testosterone and estrogen. This occurs via the production of testosterone by 17ß-HSD, its conversion into estrogen by aromatase, and activation/deactivation of Sertoli cells' AR and spermatogonia's ERα.

Seasonal changes in the prostatic complex of Artibeus planirostris (Chiroptera: Phyllostomidae).

The male reproductive accessory glands are important organs that secrete products that ensure the survival, viability and motility of spermatozoa, not only in the male reproductive tract, but also in the female. Most studies relating to the reproduction of bats do not include these glands, and detailed studies of these glands describing annual variations in the morphology and physiology are scarce. The aim of this study was to evaluate the impact of these variations on morphophysiology of the prostatic complex (PC) of Artibeus planirostris (Chiroptera: Phyllostomidae). Adult males were collected from June 2009 to July 2010, and the PC was subjected to various analyses. We observed that the PC showed marked variations throughout the year. Both PC and testicular weight increased synchronously with an increasing rate of circulating testosterone, from the autumn until summer, demonstrating that both organs are regulated by this hormone. Each region of the PC (ventral and dorsal) was unique and distinct. The ventral region showed the glandular lumen as a predominant component, in contrast to the dorsal introduced epithelium; acid phosphatase activity was observed in the epithelium of all acini in the dorsal region, but only in the stroma of the ventral region, in addition each region responded differently to variations in the environment and circulating testosterone. We concluded that the PC of A. planirostris produces two secretory peaks, which were related to a gradual increase in the rate of circulating testosterone, which stimulates both of the prostate regions to prepare for the two reproductive periods.

Structure, histochemistry and ultrastructure of the male reproductive accessory glands in the neotropical flat-faced fruit-eating bat Artibeus planirostris (Chiroptera: Phyllostomidae).

Chiroptera, the second largest mammalian order, presents different reproductive strategies and unique reproductive features. However, there are few reports regarding male reproductive accessory glands (RAGs) in Chiroptera. Thus, the aim of the present study was to characterise the RAGs of the exclusively neotropical bat Artibeus planirostris (Chiroptera: Phyllostomidae) macroscopically, microscopically and ultrastructurally. The RAGs were composed of a prostatic complex with two regions (ventral and dorsal) and paraurethral and bulbourethral glands, but no seminal vesicles. The ventral region had an undefined epithelium, with secretory and basal cells, and its secretions were periodic acid-Schiff (PAS) positive. The dorsal region received both deferens ducts, had a columnar pseudostratified epithelium with secretory and basal cells. There were two types of secretions from the dorsal region: one that was basophilic and another that was mixed PAS positive and PAS negative. The paraurethral glands were dispersed in the connective tissue of the urethra, whereas the bulbourethral glands were located in the penile root. Histological and ultrastructural data confirmed the prostatic nature of the ventral and dorsal regions and the holocrine nature of the ventral region, with the latter finding never having been described previously for the prostate gland. Our findings demonstrate the wide discrepancy of RAGs between A. planirostris and other mammals in terms of their composition, structure and morphology.

Annual reproductive cycle of males of the flat-faced fruit-eating bat, Artibeus planirostris (Chiroptera: Phyllostomidae).

Artibeus planirostris is an endemic species of Phyllostomid bat from the Neotropical region. Some studies have indicated that it exhibits seasonal bimodal polyestry; however, others postulate that it may be able to produce young at any time during the year. Thus, the aim of this study was to evaluate the annual variations in testicular and epididymal parameters of this species in southeast Brazil and try to understand how the reproduction of this species is regulated in this environment. Sixty mature male specimens, collected between June 2009 and May 2010, were submitted to morphometric and immunohistochemical analysis. Our study showed that A. planirostris presented a continuously active pattern of spermatogenesis throughout the year, presenting spermatozoa inside its cauda epididymis in all months, but with two pronounced peaks of spermatogenic production, one in September and other in February. We propose that the males developed these two peaks in order to produce sufficient sperm for the reproduction in a harem system and to synchronize with the female reproductive cycle, which had a bimodal polyestric pattern. Control of this variation is directly linked to the expression of the androgen receptor (AR) in Sertoli cells and to serum testosterone levels, which appear to synchronize to establish these two peaks. In the months preceding the two peaks, the testis have a higher expression of the AR, which possibly stimulates the increase in PCNA, and drives a gradual increase in the testicular parameters. Taken together the results suggest that if sperm storage happens in this species, it is of short duration.

Annual reproductive cycle of males of the great fruit-eating bat, Artibeus lituratus: Testicular variations, abiotic regulation and sperm analysis.

Artibeus lituratus is one of the most well-known bat species in the Neotropics, probably due to its high abundance and the ability to inhabit urban areas. It plays an important ecological role in the ecosystem due to its ability to disperse seeds, which contributes to the regeneration of degraded areas. Actually, the species has been used as an important experimental model for ecotoxicological studies of the impact of pesticides on male reproduction. Despite that, the reproductive pattern of A. lituratus is still controversial due to inconsistent descriptions of the reproductive cycle. Thus, the aim of the present work was to evaluate the annual variations of the testicular parameters and sperm quality of A. lituratus and analyze their responses to annual variations in abiotic factors in the Cerrado area in Brazil. Testes of five specimens were collected each month for one year (12 sample groups) and submitted to histological, morphometric, and immunohistochemical analyses. Analyses of the sperm quality were also performed. Results demonstrate that A. lituratus presents a continuously active process of spermatogenesis throughout the year, with two significant peaks in spermatogenic production (September-October and March), which indicates a bimodal polyestric pattern of reproduction. These reproductive peaks seem to be related to an increase in proliferation and, consequently, in the number of spermatogonia. Conversely, seasonal variations in testicular parameters are correlated with annual fluctuations in rainfall and photoperiod but not with temperature. In general, the species presents smaller spermatogenic indexes with a similar sperm quantity and quality to other bat species.

The marked dextro-dominance causes accentuated morphophysiological variations in the female reproductive organs of the bat Molossus molossus.

Molossus molossus is an insectivorous molossid bat that is important in the control of nocturnal insects. It is the nominal and the most representative species of the family. However, there are few studies about its reproduction. Thus, this study aimed to evaluate variations of its female reproductive organs during the different reproductive phases. Twenty adult females, divided into four sample groups (non-reproductive, early and advanced pregnancy and lactation), were submitted to morphological and morphometric analyses. Results show that the female reproductive system of M. molossus is composed of ovaries, a short bicornuate uterus, slightly convoluted uterine tubes and vagina. The system presents a distinct morphofunctional asymmetry, with a marked dextro-dominance. The right ovaries of all analyzed groups (NON, P1, P2, and LAC) showed follicles at different stages of development, a large number of interstitial glands and a small, but persistent corpus luteum. Ovulation is simple, unilateral and preferential, occurring exclusively in the right ovary. Follicular development in the left ovary usually does not pass the secondary stage. Implantation is fundic and preferential, occurring exclusively in the right uterine horn. The placenta is formed with two distinct chorioallantoic portions, one diffuse endotheliochorial, which covers the entire uterine cavity and regresses in the final stages of pregnancy, and the principal discoidal hemochorial portion, formed in the implantation site. The uterine cervix presents a pseudostratified epithelium, while the vagina has a little keratinized stratified epithelium, which does not accentually vary in the different reproductive stages, but can disrupt and shed in some cases.

Morphophysiology of the male reproductive accessory glands of the bat Pteronotus gymnonotus (Mormoopidae: Chiroptera).

Mormoopidae is an exclusive Neotropical family of bats, distributed from southern Mexico to northeastern Brazil. Possibly due to its endemic distribution and very low occurrence (rarity), descriptions of their reproductive accessory glands (RAGs) are still lacking. Thus, this study aims to characterize the male RAGs of Pteronotus gymnonotus (Mormoopidae: Chiroptera). Results demonstrate that the RAGs of P. gymnonotus is composed of a prostatic complex, comprising two regions (ventral and dorsal prostates); urethral (Littre) glands, a pair of bulbourethral and ampullary glands, with the absence of seminal vesicles. The ventral prostate has an atypical epithelium, due to its holocrine secretion; which contains numerous PAS-positive globular vesicles. The dorsal prostate has a cubic-to-columnar pseudostratified epithelium, containing fluid PAS-negative secretion. The ampullary glands present cubic-to-columnar pseudostratified epithelium, with secretion varying from granular and PAS-negative to fluid and PAS-positive. Urethral glands are dispersed in the submucosa of the urethra, while the bulbourethral glands are located in the penile root. Both glands have cubic-to-columnar pseudostratified epithelium with PAS-positive globular secretion. In conclusion, we propose that the RAGs of P. gymnonotus possibly evolved from a common emballonurid ancestor, shared with the families Phyllostomidae and Noctilionidae, but with the development of an exclusive apomorphy, the ampullary glands.

Comparative analysis of male reproductive accessory glands in bats Histiotus velatus (Vespertilionidae), Molossus rufus (Molossidae), and Peropteryx leucoptera (Emballonuridae).

Despite the high number of species and wide geographic dispersion, reproductive accessory glands (RAGs) of bats have traditionally received little attention in the literature, with some species not even having a basic description of their composition and structure. Thus, this study aimed to analyze and compare the composition, anatomy, and histology of male RAGs of bat species belonging to three of the largest (cosmopolitan) bat families: Vespertilionidae (Histiotus velatus), Molossidae (Molossus rufus), and Emballonuridae (Peropteryx leucoptera), in order to understand the variations in the bat RAGs. The results showed that the RAGs of H. velatus, M. rufus, and P. leucoptera are composed of an intra-abdominal prostatic complex, associated with the urethra, urethral glands, and a pair of inguinal bulbourethral glands; without ampullary glands or seminal vesicles. The prostatic complex can be composed of two (M. rufus and P. leucoptera) or three (H. velatus) prostatic regions, and can be compact (P. leucoptera), semi-lobed (M. rufus), or multilobed (H. velatus). Each prostatic region has unique and distinct characteristics, with the ventral region presenting a holocrine nature, exclusive to bats; while the dorsal and/or dorsolateral regions have similar characteristics to the ventral prostate of rats and to the human peripheral zone.

Testicular regression and recrudescence in the bat Eptesicus furinalis: Morpho-physiological variations and hormonal signaling pathways.

Males of the bat Eptesicus furinalis show at least one process of testicular regression, in which the testes regress and temporarily interrupt the production of sperm, during its annual reproductive cycle. As the process of spermatogenesis is under hormonal control, mainly of pituitary and androgen hormones, our aim was to analyze the morphological variations and the hormonal control of the testes of E. furinalis during the four phases of its reproductive cycle. Testes of 18 adult males, divided into four sample groups (active, regressing, regressed, and recrudescence phases), were submitted to morphological, morphometric, and immunohistochemical analyzes. The results demonstrate that the processes of testicular regression and recrudescence of E. furinalis are under the control of pituitary, androgen and estrogen hormones. The regulation is exerted mainly through the activation and cross signaling of AR and FSHR in Sertoli cells and of LHR in Leydig cells. The testicular regression appears to be activated by an inhibition/reduction of AR expression in Sertoli cells, which inhibits the proliferation and differentiation of new spermatogonia and causes the deactivation of spermatogenesis. Conversely, the testicular recrudescence occurs by the increasing of the expression of LHR in Leydig cells, and AR and FSHR in Sertoli cells, which reactivates the testicular production of androgens and estrogens, the proliferation of spermatogonia and restarts the spermatogenesis.

The process of testicular regression also impacts the physiology of the epididymis of the bat Molossus molossus, although with a delay in epididymal response due to sperm storage.

Responsible for post-testicular maturation, concentration, protection and sperm storage, the epididymis is an organ that can be easily subdivided into three segments: caput, corpus and cauda. Each epididymal region displays different morphology and functions within the sperm maturation process. Despite the great importance of this organ, studies on its morphology and hormonal control in bats remain scarce. Thus, the aim of this study was to morphologically analyze the epididymis of the bat Molossus molossus (Chiroptera: Molossidae), in order to evaluate its morphological and morphometric variations, as well as some aspects of its hormonal control during the annual reproductive cycle. For this purpose, 60 sexually adult males were used in this study, comprising five specimens collected monthly for one year to form 12 sample groups. The epididymis was subjected to morphological, morphometric and immunohistochemical analyses. The results demonstrated that the processes of total testicular regression and posterior recrudescence suffered by M. molossus also impacts the physiology of the epididymis, however, a delay in the epididymal response is seen due to the storage of sperm. Similar to other mammals, the epididymis of M. molossus has a large predominance of principal and basal cells. The epididymal seasonal variations appear to be directly correlated to rainfall and photoperiod, but not to temperature. Meanwhile, epididymal physiology appears to be regulated, at least partially, by the expression of the androgen receptor in epithelial cells, which has agonist effects on cell proliferation.

The prostate of the bat Artibeus lituratus: Seasonal variations, abiotic regulation, and hormonal control.

The prostate is an important gland that contributes to the male reproductive process, producing secretions that are essential for maintaining ideal conditions for the survival of sperm. Studies indicate a wide variation in the occurrence, morphology, and physiology of this gland in mammals, especially in bats, with this variation being related not only to the number of regions and their degree of compaction/lobulation but also to fluctuations in their functioning throughout the year. Thus, the aim of this study was to evaluate the annual morphological and physiological variations of the male prostate of Artibeus lituratus and analyze their responses to annual abiotic variations and hormonal control. Sixty sexually adult males of A. lituratus were analyzed in this study, with five specimens collected monthly. Blood samples were submitted to serum hormone measurements and the prostates were morphologically, morphometrically, and immunohistochemically analyzed. The results indicated that the two prostatic regions (ventral and dorsal) of A. lituratus had different morphology, as well as different physiology and regulation. Annual fluctuations in abiotic factors seemed to influence the dorsal region more than the ventral region. Conversely, variations on testicular factors, such as testosterone and estradiol, influenced the ventral region more than the dorsal region. Despite these differences, both prostatic regions were strongly synchronized to the main reproductive peak of the species in September. The holocrine pattern of the ventral prostate was not directly affected by abiotic factors or by factors released by the testes.

An alternative genotyping method using dye-labeled universal primer to reduce unspecific amplifications.

We proposed a modification the procedure of genotyping based in labeled universal primer and tailed primer. In the standard protocol, three primers are used in the same PCR reaction, a forward primer with tail added at the 5' end of the identical sequence to labeled universal primer with dye-fluorescent and a reverse primer. Unfortunately, the choice of a labeled primer characterized by a large number of complementary sequences in target genomes (which is more probable in larger genomes) result in unspecific amplifications (false positive) can cause absence or decrease amplification of the locus of interest and also false interpretation of the analysis. However, identification of possible homologies between the primer chosen for labelling and the genome is rarely possible from the available DNA data bases. In our approach, cycling is interrupted for the addition of the labeled primer only during the final cycles, thus minimizing unspecific amplification and competition between primers, resulting in the more fidelity amplification of the target regions.

Morphophysiological variations of the female reproductive organs of the vespertilionid bat Myotis nigricans during its different reproductive phases.

Myotis nigricans is an important species of insectivorous bat from the Vespertilionidae family, which is endemic of the Neotropics. Despite its wide distribution, no detailed study of the reproduction is found for this species. Thus, the aim of the present study was to evaluate and characterize morphological and morphometric variations of the female reproductive organs of M. nigricans during its different reproductive phases. Twenty adult females were collected, divided into four (4) sample groups, according to the reproductive status (nonreproductive, initial and advanced pregnancy and lactating), and submitted to anatomical, histological and morphometric analyses. The results demonstrated that the female reproductive organs of M. nigricans were composed of the ovaries, the uterus, the uterine tubes and the vagina, in addition to the mammary glands. The ovaries present a great number of interstitial glands and a small but persistent corpus luteum. Ovulation is simple, unilateral and non-preferential, possibly alternated in successive ovulations and may be sequential with the occurrence of postpartum estrus. The uterus is bicornuate, implantation is fundic and the placenta is chorioallantoic, discoidal and hemochorial. The vaginal epithelium is weakly keratinized and shows great disorganization during the periods of pregnancy and lactation.

Evaluation of the uterine hormonal control of the bat Artibeus lituratus during the different phases of its reproductive cycle.

Artibeus lituratus is a frugivorous bat that directly assists in the restoration of degraded habitats through the effective dispersion of seeds and fruits. Given its great importance, this work aimed to evaluate the uterine hormonal control of A. lituratus during its different reproductive phases. The uteri of 30 sexually mature adult females, five specimens for each of the six sample groups (NON, nonreproductive; P1, initial pregnancy; P2, intermediate pregnancy; P3, advanced pregnancy; LAC, lactating; P + LAC, pregnant-lactating), were submitted to analyses of serum estradiol and progesterone concentrations, in addition to immunohistochemical analyses. Both estradiol and progesterone, gradually increased during pregnancy, with a marked significant increase in P3 females. Both returned to low levels in LAC-females; however, estradiol levels decreased further in P + LAC-females, while progesterone increased in the same group. In general, signs indicative of aromatase expression were observed in the endometrium of all analyzed groups and in the placenta of bats in the gestation groups. Similarly, ERα and PR were expressed in the myometrium, endometrium and placenta at varying levels of intensity. The results indicate that the uterine microenvironment of A. lituratus is directly regulated by serum concentrations of estradiol and progesterone, and fluctuations in these concentrations control morphological and physiological changes of this organ during different phases of the reproductive cycle. RESEARCH HIGHLIGHTS: Increases in serum concentrations of estradiol and progesterone coordinate the gestational period of A. lituratus. Estradiol activates ERα, stimulating cell proliferation in the uterus, in addition to activating the expression of PR, which trigger the quiescence of the myometrium and stimulation of the secretion and differentiation of the endometrium. Results showed several similarities to humans, indicating the use of A. lituratus as an animal model in reproductive studies.

Annual reproductive cycle of males of the bat Molossusmolossus: Seasonal bimodal polyestry, testicular regression, and some aspects of the hormonal control.

Bats are mammals that play a fundamental role in the regulation of the ecosystems by, for example, controlling the insect populations. Therefore, insectivorous species, such as Molossusmolossus, have become the target of great scientific interest. Despite the different studies that exist on the species, there is still no consensus regarding its reproduction. Thus, this study aimed to analyze the morphophysiology and some aspects of the hormonal control of the testes of M. molossus (Chiroptera: Molossidae), by evaluating its morphological and morphometric variations throughout the annual reproductive cycle. Sixty sexually adult males of M. molossus were used in the study, with five specimens collected each month for one year, forming 12 sample groups. The testes of each bat were submitted to morphological, morphometric, and immunohistochemical analyses. Molossusmolossus presented an annual reproductive cycle with two peaks of spermatogenic activity, one in April and the other in September, and a period of total testicular regression in December, which has never been described. The cycle appeared to be regulated by rainfall and was, at least partially, controlled by the expression of the androgen receptor in Sertoli cells, which has agonist effects on cell proliferation.