Like most mammals, leaf-nosed bats use their noses in respiration (breathing) and olfaction (smelling). Unlike most mammals, however, these animals also use their noses to transmit echolocation calls. Each of these three functions requires space and connectivity within the relatively small nasal cavity. As a first step toward understanding the potential trade-offs in the evolution of these functions, this study seeks to understand how the morphology of the nasal cavity relates to olfaction in particular. Drawing on a diverse array of classic and cutting-edge anatomical techniques (comparative anatomy, histology, micro-CT scanning, and computational fluid dynamics), this research takes a multidisciplinary approach to understanding how form relates to function across evolutionary time in a sample of 14 species of bats. This research will lead to a better understanding of functional trade-offs in the evolution of complex systems. Questions about the relationship between form and function have a long history in evolutionary biology, and this research will make significant contributions to understanding the form-function relationship in an understudied region of the skull. As part of this research, undergraduates will be trained in generating and testing hypotheses, gathering anatomical data, and interpreting results. CT scans and computational models will be disseminated to other scientists and to the public through online databases.
Understanding how animals perceive their environment is an important goal of biology. Mammals, including humans, have remarkable sensory and cognitive abilites. One area of study that has lagged behind others is understanding how the sense of smell works. Recent research has made enormous strides in unmasking this important sense. However, the main organ for smelling, the nose, has proven difficult to study. With a combination of old (histology) and new (CT-scanning) technologies, we are finally able to answer some elusive questions about the function of the nasal cavity. How does the shape of the nose influence its function? Mammals use their noses to breathe and to smell their environment. Some species also use their noses to transmit their echolocation calls. Each of these functions may work best with a nasal cavity of a particular shape. However, we do not know to what extent structure and function are related in the nasal cavity. For this research we looked at how the shape of the nasal cavity might be related to olfaction (the sense of smell). In order for smells to be sensed by mammals, scent-laden air must reach the olfactory region of the nose, which is often located far to the back of the nasal passages. Differently-shaped nasal airways cause air to reach the olfactory region by different conduits and at different rates, and both of these parameters likely influence olfactory function. We investigated how differences in the shapes of the nasal passages of bats relate to olfactory airflow. Our results show that small scale differences in the shapes of the nasal airways produce noticeable differences in patterns of flow. We also found that the size of the dedicated olfactory region at the back of the nose is associated with patterns and rates of flow through the entire olfactory region (Figure 1). This result shows that one key anatomical difference can have dramatic influences on olfactory airflow, and presumably, olfactory function. The questions and approaches we used for this project combined aspects of biology and engineering. Increasingly, interdisciplinary research has yielded valuable insights into the structure and function of biological systems. This project added to this exciting research by investigating a biologically important yet understudied structure using sophisticated engineering techniques. As part of this project, we have made CT scansavailable for use by other researchers. We have also given presentations to the public about our work at a local "Science Cafe" outreach series. We will continue to find additional outlets to share our work with both the scientific and lay communities.