Application of modern tomographic imaging methods for the investigation of the internal anatomy of mysticete periotica and the evolution of low frequency hearing in baleen whales
Final Report Abstract
The complementary use of different imaging methods based on neutron and X-rays contributes to improve image contrast and to obtain additional structural information that allows the extraction of relevant anatomical features that are hardly accessible by conventional destructive methods. Due to the higher spatial resolution X-ray-based measurements obtain a more detailed digital replication of the analyzed cochlea than neutron-based measurements do. Since, in particular, the spatial resolution has been improved considerably in the last few years, latter measurement method still remains interesting for the investigation of paleopathological and geoarchaeological samples of fossil and recent origin. The high quality of the scan data and the reconstructed data sets enabled a comprehensive and detailed morphometric analysis. Results from our study confirm the influence of the morphology of the cochlea on the hearing ability of mammals, especially of whales. In addition, the inclusion of internal structures of the perioticum may be relevant to the unambiguous classification of new taxa, especially if very similar external features make the distinction more difficult. However, beam hardening effects are problematic when using polychromatic X-ray radiation. By suitable choice of X-ray filters, these can be minimized so that segmentation with a proper spatial resolution is possible. In particular, this effect can be seen in the comparison of fetal bone tissue, which has a low density with an adult bone tissue, which has a higher density. Another measurement problem is the dimensions of a whale skull. The non-invasive measurement of the cochlea requires the tomography of the entire skull. It is about an order of magnitude between the dimensions of the cochlea and the skull. So either the tomography of the entire skull will be of a low spatial resolution or a local tomography of a part of the skull with a centered cochlea can be made. The latter variant was used for the presented measurements. This enables a spatial resolution for a proper digital reproduction of the cochlear course. The reconstruction algorithms were adapted to this problem and therewith maintain the quality of the reconstruction.
Publications
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(2018) Relationships of cochlear coiling shape and hearing frequencies in cetaceans, and the occurrence of infrasonic hearing in Miocene Mysticeti. Foss. Rec. (Fossil Record) 21 (1) 33–45
Ritsche, Indira S.; Fahlke, Julia M.; Wieder, Frank; Hilger, André; Manke, Ingo; Hampe, Oliver
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2013. Whale ears inside and out: are low-frequency hearing and cranial shape related in early baleen whales (Cetacea, Mysticeti)? – A Joint Conference of the “Paläontologische Gesellschaft” and the “Palaeontological Society of China”, Göttingen, Germany, September 23-27, 2013. Pages 43-44 in: Reitner, J., Yang, Q., Wang, Y. & Reich, M. (eds.) Palaeobiology and Geobiology of Fossil Lagerstätten through Earth History, Universitätsverlag Göttingen
Fahlke, J.M., Ritsche, I.S. & Hampe, O.
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Capability to use LF sound as an evolutionary advantage in opening up new habitats during a time of global ocean and climate change, 20th Biennial Conference on the Biology of Marine Mammals, 2013 Dunedin, New Zealand, December 9-13, Abstracts (2013), pp. 180, Dunedin
I.S. Ritsche, F. Wieder, O. Hampe
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2014. Did whales straighten up to hear better? Potential connection between cranial symmetry and low-frequency hearing in mysticetes (Cetacea). – 7th Triennial Conference on Secondary Adaptations of Tetrapods to Life in Water, Fairfax, VA, and Washington, D.C., USA, June 2-4, 2014
Fahlke, J.M., Ritsche, I.S. & Hampe, O.
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Convergence vs. Specialization in the ear region of moles (mammalia). Journal of Morphology 2015, 276 (8), 900-914
N. Crumpton, N. Kardjilov, R.J. N. Asher
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Neutron computed laminography on ancient metal artefacts, Analytical Methods 7, p. 271-278 (2015)
F. Salvemini, F. Grazzi, N. Kardjilov, I. Manke, F. Civita, M. Zoppi
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Prenatal Cranial Ossification of the Humpback Whale (Megaptera novaeangliae). Journal of Morphology 2015, 276 (5), 564-582
O. Hampe, H. Franke, C.A. Hipsley, N. Kardjilov, J. Muller
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Mammalian development does not recapitulate suspected key transformations in the evolutionary detachment of the mammalian middle ear. Proceedings of the Royal Society B: Biological Sciences 2016, 283 (1822)
H. E. Ramírez-Chaves, S. W. Wroe, L. Selwood, L. A.Hinds, C.Leigh, D.Koyabu, N.Kardjilov, V.Weisbecker
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Relationships of cochlear coiling shape and hearing capabilities in Mysticeti, O. Hampe, D. Schwarz, M. Voss, M. (Eds.): Secondary adaptation of tetrapods to life in water, 8th International Meeting April 3–8 (2017), pp. 34, Berlin
I. Ritsche, J.M. Fahlke, A. Hilger, F. Wieder, I. Manke, O. Hampe
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(2018): X-ray and neutron tomography on the bony inner ear of baleen whales. In: MP Materials Testing 60 (2), S. 173–178
T. Arlt, F. Wieder, I. Ritsche, A. Hilger, J. Fahlke, O. Hampe, I. Manke
