A Quantitative Study of Olfactory, Non-Olfactory, and Vomeronasal Epithelia in the Nasal Fossa of the Bat Megaderma lyra

Abstract

In complexity, the mammalian nasal fossa is unparalleled among vertebrates. Although total nasal epithelial surface areas (SA) have been reported for numerous mammals, detailed quantitative reports on individual structures exist for few mammals. Here, we examine mucosal distribution in the nasal fossa of the greater false vampire bat, Megaderma lyra (Megadermatidae, Chiropera). The SA of the left nasal fossa of one adult Megaderma was measured in serial histological sections; the development of the nasal fossa was assessed using three fetal specimens. The nasal fossa of Megaderma has seven ethmoturbinals and multiple smaller interturbinals between them, all bearing olfactory mucosa. Nearly half of the total olfactory SA of the nasal fossa lines these turbinals; the remainder lines recesses and parts of the medial (septal) and lateral walls of the nasal fossa. The maxilloturbinal is diminutive, and the nasoturbinal is absent. Volumetric measurements of the fetal and adult vomeronasal organ suggest age-related reduction. Thirty-five percent of the nasal fossa is lined with olfactory mucosa, within the range reported previously for chiropterans. In Megaderma the frontal recess contributes little to total nasal SA (2% of all olfactory SA). This represents a significant departure in morphology compared to other mammals, including some bats, in which the frontal recess is much larger. The significance of the emphasis in olfactory SA distribution to central or more peripheral (paranasal) spaces could be investigated using a large sample of phylogenetically diverse mammals, such as bats. This study emphasizes the need for more histological detail to further such studies.