Penile histomorphology of the neotropical bat Eptesicus furinalis (Chiroptera: Vespertilionidae)

Abstract

External and internal penile morphologies have evolved rapidly and divergently in many mammalian orders and are extremely useful for taxonomic studies, particularly in the recovery of phylogenetic relationships. Eptesicus furinalis, a Vespertilionid bat, belongs to a taxon in which species recognition can be difficult when only traditional features are employed. Therefore, any feature that may contribute to the more accurate characterization of this taxon is relevant. In this study, we describe the histomorphology of the penis and baculum of this species after analyzing serial transverse sections and three-dimensional (3D) reconstructions. The glans penis was small with no epidermal projections and had an inverted Y-shaped baculum for most of its length. Internally, the penis contained three erectile tissues: corpus cavernosum, accessory cavernous tissue, and corpus spongiosum around the urethra. The internal anatomy of the E. furinalis penis displayed the basic vascular mammalian pattern but had certain features that were unique to this species, such as accessory cavernous tissue located dorsal and lateral to the tunica albuginea of the corpora cavernosa, a glans penis with a cone morphology, and a marked development of spongy tissue.

Morphological and histological characters of penile organization in eleven species of molossid bats

“…Unlike the condition observed in some genera of vespertilionid bats (Herdina et al, 2010;Comelis et al, 2015) where the corpora cavernosa are not part of the glans (which contains mostly accessory cavernous tissue) and for humans who do not have accessory tissue in the penis (Yiee and Baskin, 2010), both corpora cavernosa and accessory cavernous tissue are present in the glans penis of all species of molossids analyzed thus far, except for Moormopterus planiceps where Krutzsch and Crichton (1987) were unable to find this tissue. This fact supported the Smith and Madkour (1980) proposition that the absence or reduction of these tissues in bats is a derived condition.…”

“…When comparing results of the evaluated Molossidae taxa with those of Vespertilionidae already analyzed (Wimsatt and Kallen, 1952;Comelis et al, 2015;Herdina et al, 2015a,b), we found that this condition was additionally observed for some vespertilionid taxa. However, data for Eptesicus furinalis revealed that the penis corpus spongiosum is well developed in this taxon (Wimsatt and Kallen, 1952;Comelis et al, 2015), indicating that there is, in this family and more specifically in this taxon, a derived condition for this character.…”

“…Because it is a shared characteristic by most molossid taxa, it was considered basal for Chiroptera (Aronson and Cooper, 1967;Sachs et al, 1984;Krutzsch and Crichton, 1987;Ryan, 1991aRyan, , 1991bKelly, 2000). However, it is not a shared condition by all families because they were not observed in most of the Vespertilionidae and Miniopteridae specimens analyzed until now (Wimsatt and Kallen, 1952;Ryan, 1991aRyan, , 1991bComelis et al, 2015), and even in some species of molossids, for example, the Eumops species of the present work. Absence of projections on the glans of E. auripendulus, E. bonariensis, E. glaucinus and E. perotis note a derived condition for this character in these taxa.…”

“…Our results corroborate the erectile nature of this tissue that it is rich in smooth muscle cells, a condition already noted by us in a previous study of the penis of the vespertilionid Eptesicus furinalis. In this species, this tissue is responsible for the characteristic enlargement of the penis viewed externally under a stereoscopic microscope (Comelis et al, 2015).…”

“…The vascular penis is characterized by the presence of two cavernous bodies and a corpus spongiosum of the urethra. However, bat species have variations in number and arrangement of these tissues as well as great variation in glans morphology and the presence and morphology of the baculum (Harrison and Matthews, 1937;Wimsatt and Kallen, 1952;Krutzsch, 1975;Krutzsch et al, 1976;Krutzsch and Crichton, 1987;Ryan 1991aRyan , 1991bArmstrong, 2005;Hoofer et al, 2006;Herdina et al, 2010;Comelis et al, 2015). Nine species histologically analyzed presented three erectile tissues: two main onesconsidered by their development and representation in the glans.…”