Hydrodynamic aspects of particle capture byMytilus

Abstract

Available data on the size distribution of particles captured byMytilusindicates that a somewhat leaky, but non-sticky, filter with a minimum mesh size of a little over 1.0 μm is present. The side branches of the latero-frontal cirri have such a mesh and are positioned so as to filter water passing between the gill filaments. Information on the pressure distribution within the water circulation, and calculations of the pressure required to pass watet ihrough the latero-frontal filter at observed speeds, suggest that a little more than half the pressure generated by the lateral ciliary pump is required to overcome resistance in the latero-frontal filter and the remainder is required to circulate water in through the inhalant opening and out in an exhalant jet. The lateral cilia appear theoretically capable of generating sufficient power to produce the required pressures. Calculations indicate that although hydro-mechanical shear forces are unlikely to provide a significant contribution to particle capture, they may provide a means of keeping particles within the frontal current without a need for mucus, after filtration and transfer of particles to the frontal surface by the latero-frontal cirri.