FUNCTIONAL GEOMETRY OF CILIATED TENTACULAR ARRAYS IN ACTIVE SUSPENSION FEEDERS

Parallel tentacular structures with lateral cilia that produce suspens ion-feeding and respiratory hows occur repeatedly in many diverse taxo nomic groups, We use a computational hydrodynamic model of flow throug h ciliated tentacles to simulate flow rates through ciliated tentacle arrays. We examine the functional relationship of one performance meas ure, flow rate per unit length of array, to geometrical variables, suc h as cilia length, cilia tip speed and the gap between adjacent tentac les, and to hydrodynamic operating conditions, such as adverse pressur e drops across the array, We present a scaling and interpolation schem e to estimate how rates for a wide range of geometries that span many taxa, Our estimates of flow rate can be coupled with the hydrodynamic characteristics of biological piping systems to understand design trad e-offs between components of these systems. As a case study, we apply the model to the blue mussel Mytilus edulis by investigating the effec t on performance of changes in the gap between neighboring tentacles. Our model suggests that the observed gaps between tentacles in M. edul is reflect flow-maximizing geometries. Even relatively weak adverse pr essure drops have strong effects on flow-maximizing geometries and flo w rates. One consequence is that an intermediate range of pressure dro ps may be unfavorable, suggesting that animals may specialize into hig h-pressure and low-pressure piping systems associated with differences in organism size and with their strategy for eliminating depleted wat er.