Ontogenetic and phylogenetic transformations of the lacrimal-conducting apparatus among Microchiroptera

Abstract

Although there have been several reports on the structures of the lacrimal apparatus of the Chiroptera, there has been very little discussion about its morphological diversity and potential phylogenetic implications. Histological sections were used to document the anatomy of the lacrimal-conducting apparatus (LCA) in representatives of 44 chiropteran genera, including, for the first time members of Taphozous, Nycteris, Macroderma, Lavia, Hipposideros, Lonchophytta, Noctilio, Pteronotus, and Furipterus. To reconstruct the evolutionary history of the bat LCA, the distributions of the LCA features were mapped, using the computer program MacClade, onto the phylogenetic tree of Simmons and Geisler (1998). The lacrimal-conducting apparatus in the Chiroptera ground plan, characterized by a well-developed nasolacrimal duct and a narial nasolacrimal duct opening, is very similar to other eutherians. Nevertheless, several evolutionary transformations have taken place within the Microchiroptera: The nycterids and noctilionoids (phyllostomids + (mormoopids + noctilionids)) are characterized by apomorphic reduction of the LCA. However, there seems to be no correlation between the absence of the LCA and the life style of these bat groups. In rhinopomatids, rhinolophids and some megadermatids, the nasolacrimal duct is truncated, opening in a ventromedial recess of the inferior nasal meatus close to the entrance of the nasopalatine duct and the vomeronasal organ. Similarly, among Nataloids (e.g., Natalus and Thyroptera), the nasolacrimal duct is shorter and opens into the inferior nasal meatus, but it has no connection to the nasopalatine duct. In emballonurids, in which the vomeronasal organ is absent, the nasolacrimal duct opens into the nasopalatine duct (e. g., Taphozous, Saccotaimus) or very close to its nasal entrance (e. g., Coleura, Cormura, Rhynchonycteris).