Effects of particle surface properties on feeding selectivity in the eastern oyster Crassostrea virginica and the blue mussel Mytilus edulis

• Physicochemical interactions can play a role in mediating selection in bivalves.
• For oysters and mussels, DA models explained 25% and 72% of the data variation.
• In both models, wettability was more important than charge in classifying data.

The mechanisms by which bivalve molluscs differentiate among particles are not clearly understood. Recent evidence suggests that particle selection by bivalves can be mediated by interactions between carbohydrates attached to a particle's surface and lectins present in the mucus covering the feeding organs. The physicochemical surface properties of particles have also been proposed as factors contributing to particle selection. In this study, we examined the effects of surface charge and wettability of 10-μm spheres on particle selection by two species of suspension-feeding bivalves: eastern oysters (Crassostrea virginica) and blue mussels (Mytilus edulis). Microspheres were delivered to bivalves in particle-selection assays, and the proportions of spheres rejected as pseudofeces and egested as feces were determined using flow cytometry. Results suggest that when given a choice, both mussels and oysters rejected some types of microspheres (e.g., aluminum oxide) and ingested other types (e.g., polystyrene). In some assays, microspheres with very different surface charges or wettabilities were handled similarly, indicating that neither property alone was a qualifier for selection. The differences in surface properties between pairs of microspheres were also considered and used as variables in discriminant analyses. For oysters and mussels, the generated models explained ca. 25% and 72% of the variation in the data, respectively. In both models, wettability was more important than charge in classifying data into their correct group (rejected, preferentially ingested, or not selected). Results from this study support the idea that non-specific physicochemical interactions can play a role in mediating selection in suspension-feeding bivalves.