The information presented here represents preliminary research as the result of ten-weeks of investigation in-residence at the National Museum of Natural History. This is not an official publication of the information.

As preliminary information, results and/or findings should not be cited as part of conclusive work. Please contact the authors first if you wish to utilize the information presented here.

Abstract

Phylogenetic relationships amongst bats are controversial. In recent years, the monophyly of genera, families, and even the order has been called into question. In light of this debate, any information that can be gained by molecular or morphological data may be helpful. While pelage and dentition are well-described, soft mouthpart morphology has been largely ignored.

We looked at structures occurring in the buccal cavity between the gums and the lips; two structures found in several taxa are papillae on the insides of the lips and a ridge between the lips and teeth. Their distribution within the Chiroptera supports Teeling et al.'s (2002) revision of bats into Yinpterochiroptera and Yangochiroptera rather than the traditional Megachiroptera and Microchiroptera.

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Introduction

Phylogenetic relationships amongst bats are controversial. Controversy now surrounds the possibility of the suborder Microchiroptera being diphyletic (Hutcheon et al. 1998, Stanhope et al. 1992). Springer et al. (2001) places Rhinolophoidea with Pteropodidae rather than with the rest of the microbats on the basis of molecular data; Teeling et al. (2002) refined these findings to exclude Nycteridae from Rhinolophoidea and to make a case for its inclusion in Yangochiroptera. In light of these debates, the need for additional data on which to base phylogenetic analyses is ever-growing.

Common morphological traits used in bat phylogenies include pelage, dentition, and skeletal structure. Soft mouth part morphology is not well-studied and is largely undescribed. We attempted to describe and characterize the taxonomic distribution of two buccal cavity traits, labial papillae and oral ridge.

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Materials and Methods

The specimens used in this study were examined under a 6X dissecting microscope. The area between the gums and the teeth was examined and all structures described. All specimens are fluid specimens from the United States National Museum (USNM) mammal collection.

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Buccal Ridge

The ridge was present between the lips and the teeth in several groups. The ridge varied in prominence, being very obvious in some species and less so in others. The ridge also varied in shape, being smooth, lobulate, or pectinate; in some species, part or all of the ridge was pigmented. In most species, the ridge began at the back of the mouth, proceeding anteriorly to the canine, where it attached to the inside of the lip. In some species, a lobe was present at the connection between the ridge and the lips.

The ridge was present in Natalidae, Furipteridae, Thyropteridae, Mystacinidae, Nycteridae, Noctilionidae, Mormoopidae, Phyllostomidae, Tomopeatinae, and parts of Pteropodidae and Molossidae.

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Labial Papillae

Papillae were either rounded or pointed (Figure 2) and varied in location within the buccal cavity. In some species, a single line of papillae was present just inside the lips on the upper or lower jaw or both. The papillae generally began proximal to the canines and continued to the corner of the mouth. In other species, papillae were distributed more extensively throughout the inside of the lips.

Papillae were present in Hipposideridae, Rhinolophidae, Pteropodidae, Megaderma lyra, and part of Phyllostomidae. Within the phyllostomids, Glossophaga commissarisi, Trachops cirrhosus, Chrotopterus auritus, Carollia brevicauda, Carollia perspicillata, Carollia subrufa, and all members of Stenodermatinae had at least some papillae on their lips.

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Discussion

Neither of these structures correlates well with general feeding patterns. Labial papillae were present in bats that consume insect prey (Nowak 1999), but also in Pteropodidae and the phyllostomids, most of which are frugivorous. An oral groove is present in bats that consume arthropods as part of their diet as well as in Pteropodidae and Phyllostomidae, and the Mystacinidae consume both insects and a significant quantity of flower parts (Nowak 1999).

Therefore no obvious correlation exists between these structures and feeding behavior. However, the present taxonomic distribution of oral groove and labial papillae might be correlated with ancestral feeding behavior. This suggests the desirability of parallel phylogenetic analyses of these characters and of feeding behavior.This new morphological data appears to support the phylogeny of Teeling et al (2002).

All members of Yinpterochiroptera possess labial papillae except Rhinopomatidae and some members of Megadermatidae. The labial papillae are also missing from Nycteridae, but Teeling et al. (2002) removed the Nycteridae from Yinpterochiroptera on the basis of molecular data and placed it in Yangochiroptera.

The members of Vespertilionidae that were examined also exhibited labial papillae, which may be an example of convergent evolution. Some phyllostomids possess labial papillae; in this family, the papillae were diverse in shape and distribution. Given the diversity of the feeding habits of this family (Gardner 1977), labial papillae may have arisen independently within the Phyllostomidae as an adaptation to certain feeding habits.

Most members of Stenodermatinae and Carolliinae are frugivorous; the labial papillae may play a role in that frugivory, a view strengthened by their presence in Pteropodidae. Chrotopterus auritus and Trachops cirrhosus also possess labial papillae in spite of being largely animalivores. These papillae may have arisen independently for a different purpose, such as sensing poisonous prey. Dalquest and Werner (1954) found that facial protuberances in bats contained glandular tissue; this may also be the case for structures within the buccal cavity.

Histological work will have to be done to determine whether the labial papillae are the same in the various taxa or whether they represent a case of convergent evolution.

The oral ridge was found in most members of Yangochiroptera. Antrozinae, Vespertilioninae, and Myzopodidae lacked the oral ridge, while Nycteridae contained it, once again placing it with the Yangochiroptera. Tomopeatinae also contained the oral ridge, while the other subfamilies that were examined did not, which supports the claims of others who place Tomopeatinae apart from the rest of Vespertilionidae (Jones et al. 2002).

The purpose of the oral ridge is unclear, though it may be glandular or salivary in nature. Another possibility is that it is a flap by which the mouth may be extended to hold more food.

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Acknowledgements

We thank Jeremy Jacobs, Louise Emmons, Chad Schennum, and Dr. Richard Thorington for lending their expertise, time, and equipment to this project, as well as Mary Sangrey, the 2002 RTP interns, and the National Science Foundation. Desmodus rotundus photo thanks to Animal Diversity Web, University of Michigan. This project was funded by a National Science Foundation Research Experiences for Undergraduates, Award DBI-9820303.

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References Cited

Dalquest, W.W., and H.J. Werner. 1954. Histological aspects of the faces of North American bats. Journal of Mammalogy 35:147-160.

Gardner, A.L. 1977. Feeding Habits. In Biology of Bats of the New World Family Phyllostomidae, part II. R.J. Baker, J.K. Jones Jr., and D.C. Carter, eds. Special Publications of the Museum at Texas Tech University 13:1-364.

Hutcheon, J.M., Kirsch, A.W., and J.D. Pettigrew. 1998. Base-compositional biases and the bat problem. III. The question of microchiropteran monophyly. Philosophical Transactions of the Royal Society 353:607-617.

Nowak, R.M. 1999. Walker's Mammals of the World. Johns Hopkins University Press, Baltimore. 6th ed.

Springer, M.S., Teeling, E.C., Madsen, O. Stanhope, M.J., and W.W. de Jong. 2001. Integrated fossil and molecular data reconstruct bat echolocation. Proceedings of the National Academy of Science 98:6241-6246.

Stanhope, M.J., Czelusniak, J., Si, J.S., Mickerson, J., and M. Goodman. 1992. A molecular perspective on mammalian evolution from the gene encoding interphotoreceptor retinoid binding protein, with convincing evidence for bat monophyly. Molecular Phylogenetics and Evolution 1:148-160.

Teeling, E.C., Madsen, O., Van Den Bussche, R.A., de Jong, W.W., Stanhope, M.J., and M.S. Springer. 2002. Microbat paraphyly and the convergent evolution of a key innovation in Old World rhinolophoid microbats. Proceedings of the National Academy of Sciences 99:1431-1436.

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ENTOMOLOGY

Sarah Garrett
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