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 37.61×10(6) cells, and daily sperm production per gram of testis averaged 209.68×10(6) 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.

Histomorphometric characterization of the intertubular compartment in the testes of the bat Sturnira lilium.

Due to the scarcity of information about the reproduction of bats, it is necessary to perform studies on different species to identify the occurrence of annual variations in their reproductive process. Therefore, the aims of this study were to describe and quantify the intertubular components within the testes of the bat Sturnira lilium and to verify whether seasonality takes place in spermatogenesis of this species. The animals were collected in different seasons and time of collection was grouped into dry and rainy seasons. Testicular fragments were routinely processed for light and transmission electron microscopies and blood samples from each animal were collected for quantification of plasma testosterone. Overall, the Leydig cells (LC) were the main intertubular component (83.2%), with abundant lipid droplets in their cytoplasm. Ultrastructural analysis indicated collagen fibers in the connective tissue and lymphatic spaces, with thin walls, surrounding the seminiferous tubules. The proportion and volume of each intertubular component did not vary significantly between seasons. On average, testosterone concentrations did not vary between rainy and dry seasons (21ng/mL). The total number of LC in the testis (50.0×10(5)) and per gram of testis (11×10(7)) did not vary nor did the Leydigosomatic Index (0.03%). Therefore, it is concluded that S. lilium had significant investment in intertubular tissues, especially in LC. Most of the variables that were assessed did not vary with season of the year, which leads to the assumption that S. lilium has a continuous reproductive cycle in southeastern Brazil.

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.