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

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.