Meeting Abstract
Turbinals are thin bones in the nasal cavities of mammals. Carnivoran turbinals originate from the maxillae, nasal, ethmoid, and frontal. Maxilloturbinals (MTs) function in respiration, preventing heat and water loss by conditioning the air in the nasal cavity. Ethmoturbinals (ETs) are located in the posterior nasal cavity and function in olfaction. This study seeks to determine if there is a relationship between MT density and latitude. Heat loss risk is higher in colder climates, thus MT density between individuals is expected to vary with climate. I predicted MT density, scaled using skull length or ET density, would positively correlate with latitude. ETs were used as a control because olfactory demands are not expected to vary by latitude. North American river otters, Lontra canadensis, were chosen for this study because the species has a broad geographic range, from Nunavut to Florida. Lontra skulls were micro-CTed and 3D models of rectangular prisms from MTs and ETs were segmented. Turbinal surface area (SA) was calculated for MTs and ETs and scaled by skull length or each other to account for allometry and/or differences in scan quality. Scaled values were compared to latitude using correlations and regressions in R. As predicted, there was no relationship between scaled ET SA and latitude. The results indicate a slight relationship between the ratio of MT to ET and latitude, indicating relative turbinal density within an individual may be important for temperature regulation. There was no relationship between scaled MT SA and latitude. This may be due to gene flow, where strong selection for dense turbinals at high latitudes overpowers selection for less dense turbinals at low ones. Alternately, dense turbinals may have little evolutionary cost in warm climates. A final possibility is the limited geographic range of the sample hindered detection of any effect.
