Dear Marmam colleagues,
My coauthors and I are pleased to announce the publication of two articles on baleen function and biomechanics, especially its role in mysticete filter feeding and the ways baleen structure indicates its use. Werth Alexander J, and Jean Potvin. Baleen hydrodynamics and morphology of cross-flow filtration in balaenid whale suspension feeding. PLoS One, DOI:10.1371/journal.pone.0150106 Abstract: The traditional view of mysticete feeding involves static baleen directly sieving particles from seawater using a simple, dead-end flow-through filtration mechanism. Flow tank experiments on bowhead (Balaena mysticetus) baleen indicate the long-standing model of dead-end filtration, at least in balaenid (bowhead and right) whales, is not merely simplistic but wrong. To recreate continuous intraoral flow, sections of baleen were tested in a flume through which water and buoyant particles circulated with variable flow velocity. Kinematic sequences were analyzed to investigate movement and capture of particles by baleen plates and fringes. Results indicate that very few particles flow directly through the baleen rack; instead much water flows anteroposteriorly along the interior (lingual) side of the rack, allowing items to be carried posteriorly and accumulate at the posterior of the mouth where they might readily be swallowed. Since water flows mainly parallel to rather than directly through the filter, the cross-flow mechanism significantly reduces entrapment and tangling of minute items in baleen fringes, obviating the need to clean the filter. The absence of copepods or other prey found trapped in the baleen of necropsied right and bowhead whales supports this hypothesis. Reduced through-baleen flow was observed with and without boundaries modeling the tongue and lips, indicating that baleen itself is the main if not sole agent of crossflow. Preliminary investigation of baleen from balaenopterid whales that use intermittent filter feeding suggests that although the biomechanics and hydrodynamics of oral flow differ, cross-flow filtration may occur to some degree in all mysticetes. http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0150106 Werth Alexander J, Janice M Straley, and Robert E Shadwick. Baleen wear reveals intraoral water flow patterns of mysticete filter feeding. Journal of Morphology, DOI:10.1002/jmor.20510 Abstract: A survey of macroscopic and microscopic wear patterns in the baleen of eight whale species (Cetacea: Mysticeti) discloses structural, functional, and life history properties of this neomorphic keratinous tissue, including evidence of intraoral water flow patterns involved in filter feeding. All baleen demonstrates wear, particularly on its medial and ventral edges, as flat outer layers of cortical keratin erode to reveal horn tubes, also of keratin, which emerge as hair-like fringes. This study quantified five additional categories of specific wear: pitting of plates, scratching of plates, scuffing of fringes, shortening of fringes, and reorientation of fringes (including fringes directed between plates to the exterior of the mouth). Blue whale baleen showed the most pitting and sei whale baleen the most scratching; gray whale baleen had the most fringe wear. The location of worn baleen within the mouth suggests that direct contact with the tongue is not responsible for most wear, and that flowing water as well as abrasive prey or sediment carried by the flowing water likely causes pitting and scratching of plates as well as fringe fraying, scuffing, shortening, and reorientation. Baleen also has elevated vertical and horizontal ridges that are unrelated to wear; these are probably related to growth and may allow for age determination. http://onlinelibrary.wiley.com/doi/10.1002/jmor.20510/abstract Best regards, Alex Werth _______________________________ Alexander J. Werth, Ph.D. Venable Professor & Biology Department Chair Hampden-Sydney College Box 162, Hampden-Sydney, VA 23943 434-223-6326, fax 434-223-6374 http://www.hsc.edu/Academics/Academic-Majors/Biology/Professors/Alex-Werth.html
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