Material and structural properties of fin whale (Balaenoptera physalus) Zwischensubstanz
Article first published online: 3 MAY 2013
Copyright © 2013 Wiley Periodicals, Inc.
Journal of Morphology
Volume 274, Issue 8, pages 947–955, August 2013
How to Cite
Pinto, S. J.D. and Shadwick, R. E. (2013), Material and structural properties of fin whale (Balaenoptera physalus) Zwischensubstanz. J. Morphol., 274: 947–955. doi: 10.1002/jmor.20154
- Issue published online: 13 JUL 2013
- Article first published online: 3 MAY 2013
- Manuscript Accepted: 3 MAR 2013
- Manuscript Revised: 7 FEB 2013
- Manuscript Received: 11 SEP 2012
- RES from NSERC
The oral anatomy of the fin whale (Balaenoptera physalus) consists of several major structures crucial to its engulfment method of feeding, such as stiff keratinized baleen plates, a large flaccid tongue, and a prominent vomer. One under-documented part of this anatomy is the cream white Zwischensubstanz that holds the baleen plates to the rostrum at their dorsal base. The mechanical and structural properties of Zwischensubstanz play a key role in baleen plate dynamics and, on the grand scale, contribute to baleen whales' filtration efficiency and attainment of large body size. Compression and tensile tests on the Zwischensubstanz sampled from an 18 m fin whale showed that this material unexpectedly exhibits linear isotropic behaviour with Elastic Modulus of 2.56 ± 0.60 MPa and hysteresis of 0.44 ± 0.02 in compression despite apparent unidirectional growth. Acting similar to a soft rubber, the Zwischensubstanz absorbs and dissipates the enormous forces acting on baleen plates during engulfment feeding while maintaining spacing between the plates to maximize filtration efficiency. Microscopic analysis provided images of connective tissue papillae penetrating the base of the Zwischensubstanz and developing within it to emerge as fully formed, keratinized baleen plates. The plates develop from the papillae and a connective tissue sheet within the 5–7 cm deep Zwischensubstanz. The Zwischensubstanz provides a keratin matrix of concentrically oriented fibers around each papilla forming the hard baleen plates and frayed fringes used for filter feeding. During this formation, the Zwischensubstanz remains unchanged and appears to slough away to allow the baleen plate to grow unhindered. J. Morphol. 274:947–955, 2013. © 2013 Wiley Periodicals, Inc.