137 - Morphogenesis of Nasal Turbinal Bones in Two Species of Cervids

Poster Board Number: 137
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Abstract Body : Mammalian nasal fossae are complex structures, often consisting of multiple scrolled or branched evaginations from the lateral nasal wall, the nasal turbinals. Our prior research on bats and primates reveals that different turbinals employ multiple skeletogenic mechanisms to grow, and that different turbinals grow at different rates. Here, we examine turbinal development in much larger mammals to determine if this is a broader pattern. Prenatal and perinatal specimens of two species of deer (Muntiacus reevesi and Dama dama) were studied via conventional histological methods and via diffusible iodine-based contrast-enhanced computed tomography (diceCT). In addition, one adult Muntiacus was scanned using diceCT. Ethmoturbinals attain complexity during early prenatal development via iterative “seeding” of mesenchymal condensations that add, first, more ethmoturbinals, and later, interturbinals and epiturbinals that branch away from fully chondrified preexisting structures. Perichondrial ossification may be involved in increasing the complexity of the maxilloturbinal. Results affirm prior findings on other mammals with complex nasal cavities (e.g., some bats and primates) that skeletal tissues employ multiple mechanisms in the growth and development of nasal complexity. We observe an earlier establishment of elaborate “adult-like” form in ethmoturbinals compared to the maxilloturbinal, i.e., with dorsal and ventral scrolls. However, in the adult, scrolling of the maxilloturbinal becomes more redundant with the free margins of dorsal and ventral scrolls concentrically wrapping inward. In addition, ethmoturbinal I in the adult Muntiacus does exhibit an expansion of its rostral edge, much of which is covered by vascular respiratory mucosa based on diceCT slices. These results imply that olfactory surfaces are better formed at birth, whereas respiratory parts of turbinals become more elaborate postnatally, as respiratory air conditioning demands increase. This also supports prior findings on primates that suggest olfactory parts of turbinals grow with negative allometry, whereas respiratory regions of turbinal grow isometrically relative to the rest of the cranium. Certain histological aspects that differ between species, such as Muntiacus having earlier ossification of the maxilloturbinal, require further study.