Meeting Abstract

16.5  Sunday, Jan. 4  Comparing lung size in shallow (Tursiops truncatus) and deep (Kogia spp.) diving cetaceans PISCITELLI, M.A.*; MCLELLAN, W.A.; ROMMEL, S.A.; PABST, D.A.; Univ. of North Carolina Wilmington; Univ. of North Carolina Wilmington; Univ. of North Carolina Wilmington; Univ. of North Carolina Wilmington map9270@uncw.edu

Deep diving cetaceans are hypothesized to possess enhanced thoracic flexibility to accommodate pressure-induced reductions in lung volume at depth. Thoracic morphology has only, though, been described in detail in the shallow diving (1-10m) coastal bottlenose dolphin (Tursiops truncatus). Based on Boyles and Pascals gas laws, coastal dolphins will experience a 50% decrease in air volume at 10m. In contrast, deep diving (400-800m) pygmy and dwarf sperm whales (Kogia spp.) experience a 97% decrease in air volume at depth. Thus, the kogiid thorax may potentially undergo larger changes in volume than that of the bottlenose dolphin. However, kogiids lack some of the specialized morphologies observed in bottlenose dolphins that enhance thoracic flexibility. This study investigated whether deep diving cetaceans may limit thoracic collapse by decreasing lung size relative to body size. Lung mass was measured in the bottlenose dolphin (n = 107) and both kogiid species (n = 17). One bottlenose dolphin and one dwarf sperm whale were cross-sectioned to calculate thoracic cavity and lung volumes. For any given body mass the dolphin lung weighs 2.5 times more and has a volume 2.5 times larger than that of kogiids. Interestingly, the kogiid lung mass to body mass ratio is similar to that of terrestrial mammals. The lung occupies 37% of the total thoracic volume in the dolphin and only 15% in the dwarf sperm whale. These results indicate that the deeper diving kogiids possess smaller lungs than the shallow diving bottlenose dolphin, and will experience reduced pressure-induced changes in both lung and thoracic volumes at depth.