Breaking symmetry: The marine environment, prey size, and the evolution of asymmetry in cetacean skulls
Abstract Skulls of odontocetes (toothed whales, including dolphins and porpoises) are typified by directional asymmetry, particularly in elements associated with the airway. Generally, it is assumed this asymmetry is related to biosonar production. However, skull asymmetry may actually be a by‐produ...
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crwiley:10.1002/ar.20539 2024-09-15T18:25:27+00:00 Breaking symmetry: The marine environment, prey size, and the evolution of asymmetry in cetacean skulls Macleod, C.D. Reidenberg, J.S. Weller, M. Santos, M.B. Herman, J. Goold, J. Pierce, G.J. 2007 http://dx.doi.org/10.1002/ar.20539 https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Far.20539 https://onlinelibrary.wiley.com/doi/full/10.1002/ar.20539 en eng Wiley http://onlinelibrary.wiley.com/termsAndConditions#vor The Anatomical Record volume 290, issue 6, page 539-545 ISSN 1932-8486 1932-8494 journal-article 2007 crwiley https://doi.org/10.1002/ar.20539 2024-08-30T04:12:41Z Abstract Skulls of odontocetes (toothed whales, including dolphins and porpoises) are typified by directional asymmetry, particularly in elements associated with the airway. Generally, it is assumed this asymmetry is related to biosonar production. However, skull asymmetry may actually be a by‐product of selection pressure for an asymmetrically positioned larynx. The odontocete larynx traverses the pharynx and is held permanently in place by a ring of muscle. This allows prey swallowing while remaining underwater without risking water entering the lungs and causing injury or death. However, protrusion of the larynx through the pharynx causes a restriction around which prey must pass to reach the stomach. The larynx and associated hyoid apparatus has, therefore, been shifted to the left to provide a larger right piriform sinus (lateral pharyngeal food channel) for swallowing larger prey items. This asymmetry is reflected in the skull, particularly the dorsal openings of the nares. It is hypothesized that there is a relationship between prey size and skull asymmetry. This relationship was examined in 13 species of odontocete cetaceans from the northeast Atlantic, including four narrow‐gaped genera ( Mesoplodon , Ziphius , Hyperoodon , and Kogia ) and eight wide‐gaped genera ( Phocoena , Delphinus , Stenella , Lagenorhynchus , Tursiops , Grampus , Globicephala , and Orcinus ). Skulls were examined from 183 specimens to assess asymmetry of the anterior choanae. Stomach contents were examined from 294 specimens to assess prey size. Results show there is a significant positive relationship between maximum relative prey size consumed and average asymmetry relative to skull size in odontocete species (wide‐gape species: R 2 = 0.642, P = 0.006; narrow‐gape species: R 2 = 0.909, P = 0.031). This finding provides support for the hypothesis that the directional asymmetry found in odontocete skulls is related to an aquatic adaptation enabling swallowing large, whole prey while maintaining respiratory tract protection. Anat ... Article in Journal/Newspaper Northeast Atlantic toothed whales Wiley Online Library The Anatomical Record 290 6 539 545 |
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Open Polar |
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Wiley Online Library |
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crwiley |
language |
English |
description |
Abstract Skulls of odontocetes (toothed whales, including dolphins and porpoises) are typified by directional asymmetry, particularly in elements associated with the airway. Generally, it is assumed this asymmetry is related to biosonar production. However, skull asymmetry may actually be a by‐product of selection pressure for an asymmetrically positioned larynx. The odontocete larynx traverses the pharynx and is held permanently in place by a ring of muscle. This allows prey swallowing while remaining underwater without risking water entering the lungs and causing injury or death. However, protrusion of the larynx through the pharynx causes a restriction around which prey must pass to reach the stomach. The larynx and associated hyoid apparatus has, therefore, been shifted to the left to provide a larger right piriform sinus (lateral pharyngeal food channel) for swallowing larger prey items. This asymmetry is reflected in the skull, particularly the dorsal openings of the nares. It is hypothesized that there is a relationship between prey size and skull asymmetry. This relationship was examined in 13 species of odontocete cetaceans from the northeast Atlantic, including four narrow‐gaped genera ( Mesoplodon , Ziphius , Hyperoodon , and Kogia ) and eight wide‐gaped genera ( Phocoena , Delphinus , Stenella , Lagenorhynchus , Tursiops , Grampus , Globicephala , and Orcinus ). Skulls were examined from 183 specimens to assess asymmetry of the anterior choanae. Stomach contents were examined from 294 specimens to assess prey size. Results show there is a significant positive relationship between maximum relative prey size consumed and average asymmetry relative to skull size in odontocete species (wide‐gape species: R 2 = 0.642, P = 0.006; narrow‐gape species: R 2 = 0.909, P = 0.031). This finding provides support for the hypothesis that the directional asymmetry found in odontocete skulls is related to an aquatic adaptation enabling swallowing large, whole prey while maintaining respiratory tract protection. Anat ... |
format |
Article in Journal/Newspaper |
author |
Macleod, C.D. Reidenberg, J.S. Weller, M. Santos, M.B. Herman, J. Goold, J. Pierce, G.J. |
spellingShingle |
Macleod, C.D. Reidenberg, J.S. Weller, M. Santos, M.B. Herman, J. Goold, J. Pierce, G.J. Breaking symmetry: The marine environment, prey size, and the evolution of asymmetry in cetacean skulls |
author_facet |
Macleod, C.D. Reidenberg, J.S. Weller, M. Santos, M.B. Herman, J. Goold, J. Pierce, G.J. |
author_sort |
Macleod, C.D. |
title |
Breaking symmetry: The marine environment, prey size, and the evolution of asymmetry in cetacean skulls |
title_short |
Breaking symmetry: The marine environment, prey size, and the evolution of asymmetry in cetacean skulls |
title_full |
Breaking symmetry: The marine environment, prey size, and the evolution of asymmetry in cetacean skulls |
title_fullStr |
Breaking symmetry: The marine environment, prey size, and the evolution of asymmetry in cetacean skulls |
title_full_unstemmed |
Breaking symmetry: The marine environment, prey size, and the evolution of asymmetry in cetacean skulls |
title_sort |
breaking symmetry: the marine environment, prey size, and the evolution of asymmetry in cetacean skulls |
publisher |
Wiley |
publishDate |
2007 |
url |
http://dx.doi.org/10.1002/ar.20539 https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Far.20539 https://onlinelibrary.wiley.com/doi/full/10.1002/ar.20539 |
genre |
Northeast Atlantic toothed whales |
genre_facet |
Northeast Atlantic toothed whales |
op_source |
The Anatomical Record volume 290, issue 6, page 539-545 ISSN 1932-8486 1932-8494 |
op_rights |
http://onlinelibrary.wiley.com/termsAndConditions#vor |
op_doi |
https://doi.org/10.1002/ar.20539 |
container_title |
The Anatomical Record |
container_volume |
290 |
container_issue |
6 |
container_start_page |
539 |
op_container_end_page |
545 |
_version_ |
1810465956303994880 |