SELF-GENERATED VERSUS ENVIRONMENTALLY PRODUCED FEEDING CURRENTS: A COMPARISON FOR THE SABELLID POLYCHAETE EUDISTYLIA VANCOUVERI

The feeding currents produced by the branchial crown of the tube-dwelling sabellid polychaete Eudistylia vancouveri are compared with ambient currents experienced by the in situworm. The speeds of the branchial currents range between 0.025 and 0.080 cm/s and are similar to the patterns mapped by Nicol (1930) for Sabella pavonina. The ambient currents in contact with the branchial crown of a worm in the field are up to three orders of magnitude higher (33.6 m/s).When these worms are clustered together in the field, their tubes form hemispherical mounds that affect the pattern of ambient currents. Flow over the surface of the cluster is augmented in comparison to pre-cluster velocities. Thus animals within a cluster experience higher feeding currents than do solitary worms. This increase in feeding current velocity is not without potential competition for food from clustermates. Depletion of natural particles during the passage of a single wave through a cluster ranges from 45 to 65%.