Elastic Modulus of Cetacean Auditory Ossicles

Authors

  • Andrew A. Tubelli,

    Corresponding author
    1. Department of Biomedical Engineering, Hearing Research Center, Boston University, Boston, Massachusetts
    • Corresponding to: Andrew A. Tubelli, Hearing Research Center and Department of Biomedical Engineering, Boston University, 44 Cummington St., Boston, MA 02215. Fax: 617-353-6766. E-mail: atubelli@bu.edu

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  • Aleks Zosuls,

    1. Department of Biomedical Engineering, Hearing Research Center, Boston University, Boston, Massachusetts
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  • Darlene R. Ketten,

    1. Department of Biology, Woods Hole Oceanographic Institution, Marine Research Facility, Woods Hole, Massachusetts
    2. Department of Otology and Laryngology, Harvard Medical School, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts
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  • David C. Mountain

    1. Department of Biomedical Engineering, Hearing Research Center, Boston University, Boston, Massachusetts
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ABSTRACT

In order to model the hearing capabilities of marine mammals (cetaceans), it is necessary to understand the mechanical properties, such as elastic modulus, of the middle ear bones in these species. Biologically realistic models can be used to investigate the biomechanics of hearing in cetaceans, much of which is currently unknown. In the present study, the elastic moduli of the auditory ossicles (malleus, incus, and stapes) of eight species of cetacean, two baleen whales (mysticete) and six toothed whales (odontocete), were measured using nanoindentation. The two groups of mysticete ossicles overall had lower average elastic moduli (35.2 ± 13.3 GPa and 31.6 ± 6.5 GPa) than the groups of odontocete ossicles (53.3 ± 7.2 GPa to 62.3 ± 4.7 GPa). Interior bone generally had a higher modulus than cortical bone by up to 36%. The effects of freezing and formalin-fixation on elastic modulus were also investigated, although samples were few and no clear trend could be discerned. The high elastic modulus of the ossicles and the differences in the elastic moduli between mysticetes and odontocetes are likely specializations in the bone for underwater hearing. Anat Rec, 297:892–900, 2014. © 2014 Wiley Periodicals, Inc.

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