Meeting Abstract

P3.135  Thursday, Jan. 6  Flow-Dependent Porosity of Baleen WERTH, A.J.; Hampden-Sydney College awerth@hsc.edu

Despite its vital function in a highly dynamic environment, baleen is typically assumed to be a static material. Its biomechanical properties have not previously been explored. Small sections of bowhead whale (Balaena mysticetus) baleen were tested, either alone or in groups representing miniature “racks,” in a flow tank through which water and buoyant particles circulated with variable flow velocity and volume flow rate. Kinematic sequences were recorded through an endoscopic camera or viewing window. One set of experiments analyzed baleen fringe behavior, including fringe spacing, movement, and interaction; another experimental series investigated particle capture rate by the long baleen fringes of this species, which unlike most mysticetes feeds by continuous filtration. Bowhead baleen fringe porosity directly correlates (in mostly linear fashion) with velocity of incident water flow. Additionally, fringes undulate and interact (overlap and tangle) more at higher flow velocities. Fringe porosity depends on distance from the baleen plate. Porosity also varies (with fringe length) by position along the length of an individual baleen plate. Orientation of the baleen plates (which was altered from 0-90° relative to water flow) is critical in both fringe spacing and particle capture. At all flow velocities, porosity is lowest with crossflow filtration (plates aligned parallel to water flow). However, turbulence introduced when plates are rotated perpendicular to flow increases fringe interaction, forming a meshwork to better trap particles; hence particles more easily strike fringes without laminar flow, yet they more readily dislodge. Preliminary investigation of baleen from species that employ intermittent filtration (e.g., humpback) reveals different biomechanics.