PARTICLE SURFACE PROPERTIES AND THEIR EFFECT ON PARTICLE CAPTURE IN SUSPENSION-FEEDING BIVALVE MOLLUSCS  

The capabilities of suspension-feeding bivalve molluscs to ingest or reject certain particles selectively are well known. Recently, physicochemical properties of particles have been shown to play a role in mediating post-capture selection in these molluscs. In particular, particle surface charge and wettability, a proxy for surface hydrophobic forces, can be used by different bivalve species as qualifiers for selection. Although the role of surface properties in post-capture selection is being defined, how these physicochemical factors affect capture has been little studied. The goal of this project was to address how specific and non-specific chemical interactions affect particle capture efficiency (CE).

The effects of various physicochemical properties on particle capture were experimentally examined on two species of bivalve molluscs; the blue mussel, Mytilus edulis, and the bay scallop, Argopecten irradians. These animals have a filibrianchiate gill, with differing ciliary microstructure. M. edulis has well developed laterofrontal cirri, capable of efficiently capturing 2 to10µm particles. In contrast, A. irradians has shorter laterofrontal cilia, and cannot efficiently capture 2 to 7µm particles. Carboxylated polystyrene particles, both unbound and covalently bound with different neoglycoproteins (N-acetyl-glucosamide, D-mannose), or bovine serum albumin (BSA), were used in a series of adhesion assays and CE experiments. First, the mucus from the gill of each species was separately isolated and fixed onto microscope slides. Slides with adhered mucus were then incubated with a solution containing the manipulated particles, and particle adhesion to the mucus quantified. Secondly, treated particles of different sizes (2 to 10-µm) were directly delivered to the inhalant aperture of the mussels and scallops, the exhalent water was sampled, and CE calculated.

In M. edulis, presence of surface sugars significantly decreased particle adhesion to the mucus-covered slides (P < 0.05). Preliminary results suggest that in scallops, the presence of these surface sugars had no effect on particle adhesion to mucus (P > 0.05). Results for in vivo capture by mussels matched results from the adhesion assays, with the presence of bound sugars decreasing CE (Table 1). In scallops, presence of BSA significantly decreased CE of particles (Table 2). Preliminary findings suggest that in the smaller size ranges, the surface characteristics and presence of epicellular sugars can affect capture efficiency.