Passive suspension feeding in Amphiura filiformis (Echinodermata: Ophiuroidea): feeding behaviour in flume flow and potential feeding rate of field populations

Experimental studies in a laboratory flume show that the sediment-living brittle-star Amphiura filiformis captures suspended particles. Feeding activity is a function of now velocity with few animals extending feeding arms in still water. Flow velocity also affects the orientation of feeding arms, and we suggest that this orientation is partly controlled by A. filiformis. By combining field measurements of current velocity and seston concentration with morphometrics and filtration models, a theoretical encounter rate of suspended particles was calculated for A. filiformis. In terms of organic content, A. filiformis can potentially balance growth and respiration with ingested seston although balance will strongly depend on retention efficiency and particle quality. Detailed measurements of flow around feeding arms revealed complex now patterns that will limit the applicability of available models of food encounter for passive suspension feeders, but our sensitivity analysis indicates that suspended aggregates may be especially important in the nutrition of this species.