Histomorfometria testicular e processo espermatogênico do morcego Artibeus planirostris (Chiroptera: Phyllostomidae)

Abstract

Bats act in several ways to regulate ecosystems. Among its representatives, Artibeus planirostris is a frugivorous species, which acts both as a seed disperser and as a pollinator. Due to the scarcity of studies on the reproductive biology of bats, especially in males, and the lack of information about the reproduction of the specimens of order chiroptera in the Brazilian Northeast, this study aimed to quantify the spermatogenic process of A. planirostris, as well as its seasonal variation, through the morphological and morphometric analysis of the testes. The animals were collected in the years of 2013 and 2014, between the dry (n = 10) and rainy seasons (n = 10), at the central campus of the Federal University of Rio Grande do Norte (Natal-RN). After euthanasia, the testes were collected and processed histologically for embedding in historesin and analyzed under light microscopy. The histological slides were photographed and the morphometry was performed using the Image-Pro Plus software. The results of morphometry and biometry were compared by the Kruskall Wallis test or by the Student test, with a significance level of 5% (p <0.05). Considering the two seasons, the animals had a mean gonadosomatic index of 0,54%. The seminiferous tubules represented about 92% of the testicular parenchyma, the remaining being represented by the intertubule. The seminiferous tubules were composed of about 27% of lumen, 60% of seminiferous epithelium and 4% of tunica propria. Among the analyzed morphometric parameters, only the lumen showed significant variation between the seasons, so that the highest percentage was found in the rainy season, with about 29%. The tubular diameter and height of the seminiferous epithelium presented a mean of 142 μm and 43 μm, respectively. It was obtained a mean tubular length per gram of testis of 64.7 m and tubulesomatic index of 0.47%. The cell population of the seminiferous epithelium was composed of spermatogonia, primary spermatocytes in the transition from pre-leptotene to leptotene, zygotene and pachytene, rounded and elongated spermatids and Sertoli cells. Only the population of primary spermatocytes in pre-leptotene/leptotene presented variation between seasons, with higher values in the dry season. The annual mitotic index was 14%, the meiotic index was 3%, the overall spermatogenesis yield was 51 cells and the Sertoli cell index was 6 cells. The analysis of the frequency of the stages that compose the seminiferous epithelium cycle showed that the most and least frequent stages were, respectively, the 1 and the 6. Stages 1 and 4 varied statistically between seasons, with stage 1 being more frequent in the rainy season and stage 4 being more frequent in the dry season. The intertubule was predominantly composed of Leydig cells, which presented higher percentages in the testicular parenchyma in the dry season, as well as the volumetric proportion of the lymphatic vessels. The other intertubular components did not vary statistically between the seasons, as well as the parameters analyzed for Leydig cell morphometry. These cells presented a number per gram of testis with an annual mean of 5,63x107 cells and a Leydyssomatic index of 0.005%. It were observed a large investment in seminiferous tubules, with a low support capacity by Sertoli cells, and great investment in Leydig cells in the testicular parenchyma, especially in the dry season, as well as in the population of pre-leptotene/leptotene primary spermatocyte, indicating annual continuous spermatogenic pattern in the Northeast of the Brazil in A. planirostris.