Auditory anatomy and sound reception in the Beluga whale (Delphinapterus leucas) compared to the Bottlenose Dolphin (Tursiops truncatus)

TitleAuditory anatomy and sound reception in the Beluga whale (Delphinapterus leucas) compared to the Bottlenose Dolphin (Tursiops truncatus)
Publication TypeConference Poster
AuthorsYamato, M., A. Mooney, D. R. Ketten, S. R. Cramer, and J. J. Arruda
Conference Name18th Biennial Conference on the Biology of Marine Mammals
Conference LocationQuebec, Canada
Year of Publication2009
Date Published10/2009
Publication Languageeng

Current theories of sound reception in odontocetes are based primarily on experiments and anatomical observations from one species, the bottlenose dolphin (Tursiops truncatus). Generalizations about sound reception pathways must be made with caution because there are many variations in cranial and mandibular morphology among odontocete species which suggests potential subtle differences in sound reception. In this study, the auditory anatomy and fatty sound reception pathways in the beluga whale (Delphinapterus leucas) and the bottlenose dolphin were compared using three-dimensional reconstructions from computerized tomography (CT) data. The beluga was selected because the Monodontidae have a substantially different head structure from the Delphinidae, particularly in terms of rostrum and lower jaw conformation, and comparative data on hearing ranges, sensitivities, and localization are available for both species. The CT images employed were obtained with a maximal resolution of 0.1 mm, allowing features from gross skeletal to inner ear labyrinths to be determined. The reconstructions show that the general positions and distributions of acoustic fats are similar in the beluga whale and the bottlenose dolphin. However, there are subtle differences that may influence hearing pathways, including the configuration and dimensions of the jaw fats. In particular, the postero-lateral jaw fats that are speculated to serve as an additional acoustic path for lower frequencies in bottlenose dolphins are less evident in the beluga whale. These fats are located ventral to the external auditory meatus in both species, a region that has never been tested for acoustic sensitivity in the beluga whale. These comparative data suggest that there are sufficient differences not only in the skull but also in the soft tissues of the heads of cetaceans to warrant species-specific studies of auditory anatomy and sound reception pathways. In particular, there may be important differences in key functional anatomical features across families.

Keywordsanatomy, auditory, beluga whale, bottlenose dolphin, delphinapterus leucas, sound reception, tursiops truncatus
Citation Key12