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Capture of Large Particles by Suspension-Feeding Scaleworm Larvae (Polychaeta: Polynoidae)

Friday Harbor Laboratories, 620 University Road, Friday Harbor, Washington 98250, and Department of Zoology, University of Washington, Box 351800, Seattle, Washington 98195-1800

Most of the polychaete larvae in which feeding mechanisms have been studied feed using an opposed-band mechanism, capturing particles with prototrochal and metatrochal ciliary bands and transporting them to the mouth via a food groove. However, many other planktotrophic polychaete larvae lack a metatroch and food groove and thus must feed in a different way. In this latter group are the larvae of polynoid polychaetes, which not only lack a metatroch and food groove but also bear a bundle of long cilia (the oral brush) attached near the left side of the mouth. In feeding experiments with polystyrene beads and plankton, larvae of the polynoid Arctonoe vittata ingested larger particles (up to 60 {mu}m in diameter) than those ingested by the opposed-band feeding larvae of the serpulid Serpula vermicularis (up to 12 μm in diameter). Videotaped images of feeding A. vittata larvae showed that capture behavior was elicited as particles in a feeding current driven by the prototroch approached or contacted the larval episphere. Particles on or very near the episphere were disengaged by a recoiling motion of the larva and were then moved to the mouth, probably by the oral brush. This feeding mechanism may be widespread in the polychaete superfamily Aphroditacea, which includes about 10% of extant polychaete species.