Espermatogênese no morcego Sturnira lilium (Chiroptera: Phyllostomidae): aspectos morfológicos, morfométricos e ultraestruturais

• Autor(a) principal: Morais, Danielle Barbosa
• Data de Publicação: 2012
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/255
• topic: Reprodução em morcegos; Testículo; Ciclo do epitélio seminífero; Célula de Sertoli; Célula de Leydig; Reproduction in bats; Testis; Seminiferous epithelium cycle; Sertoli cell; Leydig cell; CNPQ::CIENCIAS BIOLOGICAS::BIOLOGIA GERAL

The bat Sturnira lilium has a dietary habit predominantly frugivorous, being an important pollinator, especially for plant species that depend on bats for pollination and dispersal of their seeds. Due to its importance, it becomes essential to know how this bat species reproduces, as well as if there is influence of environmental factors on their reproductive cycle, since this influence has been reported for several bat species. Once little information is available about the quantification and characterization of spermatogenesis in bats, this study aimed to provide information about testicular activity of S. lilium throughout the annual climatic seasons. To this end, we performed a morphological and morphometric characterization, with calculation of indices indicative of sperm production, characterization of the stages that compose the seminiferous epithelium cycle, and quantification of its androgenic capacity, in the testes of adult individuals. Thus, 14 animals were captured in the dry (n = 7) and rainy seasons (n = 7), in Viçosa city-MG. After euthanasia, testicular fragments were processed histologically for morphological, morphometric and histochemical analysis by light microscopy and ultrastructural analysis under transmission electron microscopy. The animals showed GSI average of 0.27 %, and their testes followed the general organization described for mammals. The ultrastructural analysis allowed observing the formation of the acrosomal cap in round spermatids, besides the characterization of other cells that compose the tubular compartment. Considering both seasons, the testicular parenchyma was composed of about 85 % of seminiferous tubules and 15 % of intertubule, and the tubular length per gram of testis had approximately 80 m. There was no difference in the count of apoptotic cells between the seasons. The highest spermatic reserve of the testes was observed during the rainy season, with 43.47x106 cells, as well as the daily sperm production, whose average was 12.60x106 cells at the same season. The presence of primary spermatocytes at zygotene in the stage 1 of the seminiferous epithelium cycle, according to the tubular morphology method, differs from many mammalian described so far. The animals of this study showed an average mitotic index of 15.4 cells, meiotic index of 2.9, general yield of spermatogenesis of 68.7 cells, and support capacity of the Sertoli cells of 7.0 cells. The duration of one seminiferous epithelium cycle was 3.45 days, and approximately 15.52 days were required for development of sperm from spermatogonia. Leydig cells were the main component of intertubule, followed by blood vessels, connective tissue and lymphatic space. The number of Leydig cells per gram of testis, whose average was 11x107 cells, showed no significant difference throughout the seasons, as well as the Leydigosomatic index (mean of 0.03 %) and the plasmatic levels of testosterone (mean of 21 ng/ml). The ultrastructural analysis revealed abundant lipid droplets in the cytoplasm of Leydig cells, as well as collagen fibers in connective tissue and lymph spaces with thin walls, surrounding the seminiferous tubules. S. lilium showed tubular length per gram of testis above the observed in other mammals, in contrast to the lowest ever recorded for the spermatogenic process. It was also observed high efficiency of spermatogenesis, low carrying capacity by Sertoli cells and a large investment in Leydig cells. It can be concluded that bats S. lilium males have annual reproductive pattern continuous at the area of study, once that the quantification of great part of the tubular and intertubular components, as well as testosterone levels remained constant throughout the year.