THE FEEDING BIOLOGY OF PODARKE PUGETTENSIS (POLYCHAETA: HESIONIDAE)

¹ Department of Biology and Belle W. Baruch Institute for Marine Biology and Coastal Research, University of South Carolina, Columbia, South Carolina 29208

1. Podarke pugettensis is carnivorous, ingesting a wide variety of small benthic invertebrates, including members of at least 11 polychaete families. Harpacticoid copepods constituted the bulk of the diet in the field population examined. Food items are limited to those that are small relative to the predator and can fit through its pharynx. Plant material and sediment are not ingested purposely, but may enter the gut by being sucked in with the prey, or by being within the gut of the prey.

2. Ingested animals appear to be thoroughly digested by the time they reach the hindgut, while plant material appears to be undigested. The gut passage time is generally 12 to 24 hr, indicating a slow movement and thorough digestion of animal material. The long gut passage time may be necessary because Podarke is limited in the food it consumes by relative prey availability, and so must digest food as thoroughly as possible.

3. The unarmed pharynx acts as a double-action pump, with two thick-walled muscular regions and two thinner-walled valves. The massive walls of the muscular regions consist mostly of radial muscle fibers which can rapidly open the pharynx, sucking in prey.

4. Podarke pugettensis appears to utilize vibration sensing, direct touching, and chemoreception to detect and evaluate potential prey. Size of the prey appears to be the most critical factor influencing prey selection.

5. Calculations of feeding rate of Podarke indicate that this predator could consume a significant portion of the production of co-occuring benthic copepod populations.