A comparison of tracheal morphology and elastin abundance in bottlenose dolphin (cetacea: tursiops truncatus) and white-tailed deer (artiodactyla: odocoileus virginianus)

Odontocete species exhibit diving strategies to exploit various resources in marine waters. While the phenomenon of lung collapse has been studied, the morphology and fine structure of the respiratory conducting regions are largely unexplored. A comparison of elastin abundance and tracheal morphology between marine and terrestrial mammals is needed to explore this question. The aim of this study was to compare and contrast the tracheal regions between two species of mammal that experience a wide differential in pressure gradients. Tracheae from Atlantic bottlenose dolphins (Tursiops truncatus) and white-tailed deer (Odocoileus virginianus) were collected and examined using gross morphology and light microscopy. This study showed that differences in tracheal dimensions, architecture, cartilaginous ring structure and elastin abundance were the result of divergent adaptations to lifestyles exploiting very different environments. There was a significant difference in elastin coverage (percent) with more elastin in Tursiops truncatus than in Odocoileus virginianus. The respiratory system of terrestrial Odocoileus virginianus evolved for flexibility and increased range of motion; whereas, the odontocete airway became more compact, rigid and reinforced to contend with the increased pressures associated with an aquatic environment.