Light microscopic and ultrastructural observations on the vomeronasal organ of Anoura (Chiroptera: Phyllostomidae)

Abstract

The vomeronasal organ (VNO) is known to be present in bats of the family Phyllostomidae, but in most species this is inferred from the presence of accessory olfactory bulbs. Like primates, bats have profound intergroup variations in the vomeronasal system. Of the family Phyllostomidae (49 genera, 143 species) the VNO of approximately 60 species has been studied. Here, we report light microscopic observations of the VNO of Anoura geoffroyi (fetus and adult), A. caudifer, and A. cultrata, as well as ultrastructural observations of the VNO in adult A. geoffroyi. The organ is crescent-shaped, with a wide lumen encroached by a "mushroom body" that contains a venous sinus. In adults, the vomeronasal cartilage is reduced, being longer in absolute length in fetal A. geoffroyi compared with the adult. In the neuroepithelium, the receptor cell microvilli are dark, distinct, and short, emerging from a vesicular tuft; the supporting cell microvilli are relatively much longer. Large paravomeronasal ganglia are observed. The receptor-free epithelium is undulating and lacks cilia or microvilli. Some characteristics of the VNO in Anoura have not been reported in other chiropterans to date, such as the marked reduction of the vomeronasal cartilage and absence of cilia in the receptor-free epithelium. Moreover, if A. geoffroyi is representative, the genus has an adult neuroepithelial volume similar to other mammals of its body size. Further examination of uninvestigated phyllostomid VNOs may elucidate a phylogenetic history of the family, as well as ecological or social correlates of the VNO in the order Chiroptera.