The Nose of the Sperm Whale: Overviews of Functional Design, Structural Homologies and Evolution Stefan Huggenberger1,2, Michel Andre’ 3 and Helmut H
Journal of the Marine Biological Association of the United Kingdom, page 1 of 24. # Marine Biological Association of the United Kingdom, 2014 doi:10.1017/S0025315414001118 The nose of the sperm whale: overviews of functional design, structural homologies and evolution stefan huggenberger1,2, michel andre’ 3 and helmut h. a. oelschla¤ger4 1Biocentre, University of Cologne, 50923 Cologne, Germany, 2Department of Anatomy II, University of Cologne, 50924 Cologne, Germany, 3Laboratori d’Aplicacions Bioacu´stiques, Universitat Polite`cnica de Catalunya, Centre Tecnolo`gic de Vilanova i la Geltru´, Avenida.Rambla Exposicio´, s/n, 08800 Vilanova i la Geltru´, Barcelona, Spain, 4Department of Anatomy III (Dr Senckenbergische Anatomie), Johann Wolfgang Goethe University of Frankfurt am Main, 60590 Frankfurt am Main, Germany The hypertrophic and much elongated epicranial (nasal) complex of sperm whales (Physeter macrocephalus) is a unique device to increase directionality and source levels of echolocation clicks in aquatic environments. The size and shape of the nasal fat bodies as well as the peculiar organization of the air sac system in the nasal sound generator of sperm whales are in favour of this proposed specialized acoustic function. The morphology of the sperm whale nose, including a ‘connecting acoustic window’ in the case and an anterior ‘terminal acoustic window’ at the rostroventral edge of the junk, supports the ‘bent horn hypothesis’ of sound emission. In contrast to the laryngeal mechanism described for dolphins and porpoises, sperm whales may drive the initial pulse generation process with air pressurized by nasal muscles associated with the right nasal passage (right nasal passage muscle, maxillonasolabialis muscle). This can be interpreted as an adapta- tion to deep-diving and high hydrostatic pressures constraining pneumatic phonation.
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