Morphology of the core fibrous layer of the cetacean tail fluke

• Published in: Journal of Morphology
• Main Authors: Gough, William T., Fish, Frank E., Wainwright, Dylan K., Bart‐Smith, Hilary
• Other Authors: Office of Naval Research
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2018
• Subjects: Developmental Biology; Animal Science and Zoology; Sperm whale
• Online Access: http://dx.doi.org/10.1002/jmor.20808; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fjmor.20808; https://onlinelibrary.wiley.com/doi/pdf/10.1002/jmor.20808; https://onlinelibrary.wiley.com/doi/full-xml/10.1002/jmor.20808; https://onlinelibrary.wiley.com/doi/am-pdf/10.1002/jmor.20808

Abstract The cetacean tail fluke blades are not supported by any vertebral elements. Instead, the majority of the blades are composed of a densely packed collagenous fiber matrix known as the core layer. Fluke blades from six species of odontocete cetaceans were examined to compare the morphology and orientation of fibers at different locations along the spanwise and chordwise fluke blade axes. The general fiber morphology was consistent with a three‐dimensional structure comprised of two‐dimensional sheets of fibers aligned tightly in a laminated configuration along the spanwise axis. The laminated configuration of the fluke blades helps to maintain spanwise rigidity while allowing partial flexibility during swimming. When viewing the chordwise sectional face at the leading edge and mid‐chord regions, fibers displayed a crossing pattern. This configuration relates to bending and structural support of the fluke blade. The trailing edge core was found to have parallel fibers arranged more dorso‐ventrally. The fiber morphology of the fluke blades was dorso‐ventrally symmetrical and similar in all species except the pygmy sperm whale ( Kogia breviceps ), which was found to have additional core layer fiber bundles running along the span of the fluke blade. These additional fibers may increase stiffness of the structure by resisting tension along their long spanwise axis.