Indira S. Ritsche‡, Julia M. Fahlke‡, Frank Wieder§, André Hilger|, Ingo Manke|, Oliver Hampe‡© Indira S. Ritsche, Julia M. Fahlke, Frank Wieder, André Hilger, Ingo Manke, Oliver Hampe. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Citation:
Ritsche IS, Fahlke JM, Wieder F, Hilger A, Manke I, Hampe O (2018) Relationships of cochlear coiling shape and hearing frequencies in cetaceans, and the occurrence of infrasonic hearing in Miocene Mysticeti. Fossil Record 21(1): 33-45. https://doi.org/10.5194/fr-21-33-2018 |  |
Baleenwhales (Mysticeti) are known to use low frequencies (LF; 200 Hz and below)and infrasound (< 20 Hz) for communication. The lowest hearinglimits of toothed whales (Odontoceti), which are able to produce ultrasound(> 20 kHz), reach low frequencies. Researchers have tried tounderstand the evolution of LF and infrasonic hearing in mysticetes bylinking the shape of the inner ear cochlea or individual cochlearmeasurements to known hearing frequencies and making inferences to extinctspecies. Using landmark-based shape analysis of complete cochlear coiling, weshow that cochlear coiling shape correlates with LF and high-frequency (HF;> 10 kHz) hearing limits in cetaceans. Very LF (≤ 50 Hz)and infrasonic hearing are associated with, for example, a protruding second turn, adescending apex, and a high number of turns. Correlations between cochlearand cranial variables and cochlear and cranial shape indicate that low LFhearing limits are furthermore connected to longer cochleae and relativelylarger cranial widths. Very LF hearing in Mysticeti appeared in the middleMiocene, and mysticete infrasonic hearing had evolved by the late Miocene.Complete cochlear coiling is suitable for estimating hearing limits incetaceans, closely approximated by cochlear length times number of cochlearturns.