Fluid motion and particle retention in the gill of Mytilus edulis: Video recordings and numerical modelling

Minireview: Ciliary filter feeding and bio‐fluid mechanics—present understanding and unsolved problems

“…Transfer of particles is accomplished by the compound LFC or by the water currents they generate as they beat against the current through an angle of 90Њ. Particles Ͼ4 m are stopped and transferred to the frontal side, whereas smaller particles either follow the flow around the cirri or they are stopped by the cirri's branching cilia (Dral 1967;Owen and McCrae 1976;Silvester and Sleigh 1984;Riisgård 1988b;Jørgensen 1990Jørgensen , 1996Beninger et al 1992, Nielsen andLarsen 1993;Nielsen et al 1993;Riisgård et al 1996a). A ''new explanation'' of particle capture in mussels, based on endoscopic observations of an apparent low angle (ഠ30Њ) of particles approaching the gill filaments and subsequent direct interception, has been proposed by Ward (1996) and Ward et al (1998Ward et al ( , 2000, but Riisgård and Larsen (2000) raised doubt about its bio-fluid mechanic foundation.…”

“…Here, as in many other models, the ciliary motion, including metachronism, is prescribed a priori. It has been used as an approximation to determine the pump characteristic of an idealized pump consisting of a long, twodimensional channel with ciliated walls (Nielsen and Larsen 1993). In the sublayer model (Blake 1972), each cilium is modeled by singularities appropriate for low Reynolds number Stokes flow.…”

“…Because of the geometric and kinematic complexities, scaled-up laboratory models are largely ruled out, and therefore in situ observations are needed. Available observation techniques include high-speed cinefilms recorded through microscopes (Nielsen and Rostgaard 1976;Strathmann 1982;Emlet 1990), regular video microscopy (e.g., Gallager 1988;Nielsen et al 1993;Hart 1996;Petersen et al 1999), confocal laser microscopy (Silverman et al 1996Beninger et al 1997a), and endoscopy (Beninger et al 1992(Beninger et al ,. 1997bBeninger and St-Jean 1997;Ward et al 1996Ward et al , 1998Ward et al , 2000.…”

The utility of in vivo observations for describing particle capture processes in suspension‐feeding bivalve molluscs

“…3 is not a ''schematic,'' but represents ob-Comment servations from several consecutive video images which allowed us to discern four basic patterns of particle encounters with the ctendial filament (Ward et al 1998; see Web video ''Particle tracking''). This approach of overlaying consecutive video frames to make a composite for presentation on the printed page is a standard technique applied by researchers who use video data (e.g., Hart 1991;Nielsen et al 1993;Mayer 1994).…”

“…Ward et al (1998) used such observations combined with results from experimental manipulations (e.g., serotonin additions to inactivate laterofrontal cirri) as surrogates for visualizing the cilia directly, enabling them to study indirectly the net effects of cilia and cirri on particle capture. This approach of using particle motion to examine the interactions between particles and ciliated surfaces is widely used (Hart 1991;Nielsen et al 1993;Mayer 1994;Riisgård et al 1996) and, indeed, was used by Riisgård and Larsen (2000). Studying ciliary processes indirectly differs greatly from direct observations of the action of cilia on tissues that have been dissected from the animal using higher magnification microscopes (e.g., Riisgård et al 1996;.…”