TISSUE LOSS INDUCES SWITCHING OF FEEDING MODE IN SPIONID POLYCHAETES

For many animals, foraging is a complex activity involving decisions o f when, where, and how to feed, as well as what to feed upon. Flexibil ity in foraging (i.e. switches among activities, habitats, or food ite ms) is presumed to contribute to overall fitness, and is an important component of theoretical models of animal feeding behavior. The import ance of switching among feeding methods is less well described, but ma y be very important for marine sediment dwellers (infauna). For exampl e, many infauna switch between suspension and surface-deposit feeding depending on water flow. However, infauna often lose feeding appendage s to browsing predators, and the ability to switch to alternative feed ing methods which are not dependent on those appendages should be adva ntageous after such tissue losses. Laboratory experiments examined the effect of feeding appendage loss on 2 species of spionid polychaetes which have different alternative feeding modes when intact. Behavior o f individual worms with 0, 1 or 2 palps removed was videotaped for 2 h within 3 to 4 d of palp removal. Loss of both feeding palps induced s witches to alternative feeding modes involving mouth-feeding: Rhynchos pio glutaeus fed on the surface, Pseudopolydora kempi japonica fed bel ow the surface. As measured by time spent feeding and by fecal product ion, the alternative was effective for R. glutaeus but not for P. k. j aponica. The results emphasize the potential importance of injury and subsequent switching as factors determining feeding behavior.