Date Published: October 17, 2018
Publisher: Public Library of Science
Author(s): Ana Cláudia Ferreira Souza, Felipe Couto Santos, Daniel Silva Sena Bastos, Marcela Nascimento Sertorio, João Paulo Gusmão Teixeira, Kenner Morais Fernandes, Mariana Machado-Neves, Carlos E. Ambrósio.
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.
Bat species inhabiting seasonal environments usually pattern their mating season to precede or coincide with periods when weather conditions and food availability are favorable for successful reproduction [1,2]. On the other hand, there are bats in which the reproductive pattern is not restricted to seasonal variations [3,4]. In males, reproductive strategies may be relied on individual body condition, food availability, expression of hormonal receptors (e.g., androgen receptor, estrogen receptor, LH receptor and FSH receptor) or testicular recrudescence [5–7]. Nevertheless, their sexual activity is strongly associated with female cycles that can be monoestrous or polyestrous, and non-seasonal or seasonal .
The body and testis weight, as well as the gonadosomatic index did not change in D. rotundus during dry and rainy seasons (P > 0.05; Table 1). Testicular sections of bats in both seasons showed normal tissue architecture, with seminiferous epithelium composed of Sertoli cells and germ cells in different developmental stages (spermatogonia, spermatocytes, round and elongated spermatids), and lumen with spermatozoa (Fig 1). Furthermore, the intertubular compartment was composed of lymphatic space, blood vessels, connective tissue, macrophages, and mainly Leydig cells (Fig 2). It was possible to observe, in both seasons, the presence of germ cells in the lumen of some seminiferous tubules (Fig 1), and lipid droplets and lipofuscin granules in the Leydig cell cytoplasm (Fig 2). Cleaved-caspase 3 labeling was detected in different cell types from both tubular and intertubular compartments of the testis. However, the number of apoptotic cells in the organ did not differ between bats during dry and rainy seasons (P > 0.05; Fig 3).
The present study compared male reproductive parameters of the common vampire bat D. rotundus during dry and rainy seasons. To our knowledge, this is the first study to evaluate testicular morphology, testosterone production, and epididymal function associated with seasons in this species. Our results showed that stereological parameters of the testis changed in the rainy season, as well as sperm counts and sperm transit time in the epididymis.
Taken together, we can conclude that stereological and morphometric parameters in the testis of the common vampire bat D. rotundus varied between dry and rainy seasons. However, the maintenance of testosterone concentration and daily sperm production indicates that the reproductive pattern in D. rotundus does not change between seasons. Studies involving sampling in every month throughout the year, and molecular approaches will be very important to confirm the reproductive pattern here presented. Notwithstanding, our data can be a baseline for management of vampire bat population as an attempt to control rabies disease.