The Functional Response of the Predatory Polychaete, Harmothoe sarsi, to the Amphipod, Pontoporeia affinis

The functional response of the predatory polynoid polychaete worm, Harmothoe sarsi to the amphipod Pontoporeia affinis was measured in the laboratory. No significant difference was detected over the 300-fold range of prey densities that the predator could encounter in the field. Four-day-long experiments with low initial prey numbers indicated that Harmothoe might reduce its intake when prey density was low and when it had recently ingested prey. Artificial selection experiments produced no evidence that variation in the escape ability of individual prey affected Harmothoe's functional response