Role of particle wettability in capture by a suspension-feeding crab (Emerita talpoida)

Abstract

Suspension feeders sometimes depend on adhesion between particle and collector to capture food. If food particles have different adhesive properties than other particles, food could be passively selected by adhesive mechanisms. In this regard, the effect of particle wettability on adhesion to artificial and natural collectors was studied. First, the adhesion of glass particles to artificial collectors, both varying in wettability, was assessed to determine if wettability influenced adhesion in seawater. The adhesive force between glass particles and artificial collectors was measured by increasing the force pulling particles away from the collector until 50% of the particles fell off the collector. Adhesion increased as particle wettability decreased. Next, glass particles were used to determine if the antennal collector of the suspension-feeding mole crab Emerita talpoida captured particles based on particle wettability. 0.5 to 10 and 15 to 25 μm particles were suspended in a recirculating flow tank filled with seawater, and ablated antennae were exposed to this flow, after which the captured particles were counted. Results for the 0.5 to 10 μm particles confirmed predictions based on results from artificial collectors; particle capture increased as particle wettability decreased. The 15 to 25 μm particles may have been captured by sieving, and consequently did not follow predictions based on adhesion. Passive selection of particles based upon wettability differences can occur.