Histomorphology of the glans penis in Eumops glaucinus, Molossus rufus and Nyctinomops laticaudatus (Chiroptera:Mammalia)

The evolution of internal fertilization resulted in arise of a vast diversity of anatomical forms in the copulatory organs, especially in the penis. Indeed, external and internal penile morphology varies widely among mammal species. The importance of the penis and its variation in morphology to the success of the reproduction in mammals is undoubted. In bats, the morphology of the penis varies between species, and this may be related, among other factors, to the different habitats they live, which may have influenced, in an evolutionary way, the morphology of the copulatory organ. Between some variations in this structure are the presence of an os penis (baculum) found in the tip of the glans, that may provide an additional rigidity for the erect penis to facilitate intromission, or may assist in sperm transport and to stimulate the female, and the presence of additional erectile tissue known as the accessory corpus cavernosus (in the glans either in the prepuce); and in the number of corpora cavernosa. So, the aim of our work was to describe the morphology of the baculum and the histomorphology of the glans of three species of Chiroptera: Eumops glaucinus, Molossus rufus and Nyctinomops laticaudatus. The penises were removed and processed for light microscopy, stained with HE. For the morphological analyses we submitted 5 penises from each species to the process of diaphonization. The baculum was isolated and analyzed under stereoscopy. In M. rufus the glans penis is larger – 4.47mm long, cone-shaped and has spine-shaped epidermal projections. It tapers toward the apex, which is constituted by three lobes. In dorsal surface there is a deep furrow in the level of urinary meatus. The glans penis of E. glaucinus is smaller- 1.61mm long, and lacks epidermal projections. Its shaft shaped, oval at its base and widens at approximately two-thirds the distance from the prepucial junction. In the ventral surface there is a medial ridge, and ending the ridge there is a circle shaped furrow, in level of urinary meatus. In N. laticaudatus the glans has 2.73mm in length, is cone shaped, tapering toward the apex and ending in a rounded bacular mount. It has spine-shaped epidermal projections, but they are smaller and more spaced than in M. rufus. In the ventral surface there is in the subapical region a circular cleft which surrounds the entire ventral portion, the urinary meatus, which separates the ventral end portion of the glans in a small rounded tip, bacular mount.The baculum of E. glaucinus has approximately 0.62 mm in length, is curved in about two-thirds of its length when viewed laterally, and narrower in the apical portion than in the basis. Already M. rufus’ baculum is lower, has about 0.34 mm in length, its shaftshaped with rounded ends, narrowing in the the midline. N. laticaudatus’s baculum has about 0.64mm, has an arrow shape in dorsal view but in lateral view it is straight until 2/3 its length, widening in the remaining third. All species exhibited a vascular penis indeed each one has particular histological features.When observed the basis of the penis all have two corpora cavernosa, but when we analyzed at the midpoint we notice that the penis of M. rufus shows three corpora cavernosa while there is no variation in the number of this tissue in the other species. The three species have another erectile tissue, which is more diffuse, called accessory corpora cavernosa, which is more developed in M. rufus and N. laticaudatus than in E. glaucinus. In M. rufus and N. laticaudatus the epithelium is covered with a deep layer of keratin, which forms the epithelial projections. Already in E. glaucinus we were able to identify a pair of dorso-lateral nerves, that are absent in the other species. According to the exhibit data we can confirm that the analyzed taxa keep the basic histological structure of vascular penis in mammals, with variations both in morphology and in histological arrangement in the penises of the three species. (IBAMA Processo: 02027.001957/2006-02).