Feeding and Burrowing Behaviors of a Deposit-feeding Capitelid Polychaete, Capitella sp. I

Abstract

Abstract: A capitelid small polychaete, Capitella sp. I, is a head-side down deposit feeder, which often occurs densely in organically enriched sediment. In this study, we observed burrowing and feeding behaviors of this species, and conducted laboratory experiments, examining the impact of reworking activities of the worms on the physics and chemistry of the organically enriched sediment. The laboratory experiments revealed that the worms fed not only the subsurface sediment but also the surface sediment selectively. The burrowing and feeding activities of the worms in the sediment were activated by the addition of organic matter on the sediment surface. The reworking activities of the worms include burrowing into the sediment, spouting the subsurface layers of the sediment onto the sediment surface, feeding on the sediment and excreting the sediment as fecal pellets on the sediment surface. The amount of spouted sediment on the sediment surface caused by burrowing activities was approximately 2.6 times larger than the amount of sediment reworked by excretion of fecal pellets. We estimated that approximately 162gDW per day of the sediment could be reworked by 30, 000 adult worms with 1 mm of maximum width of thoracic segments. This reworking rate indicated that one square meter of the subsurface sediment with 2 cm in thickness, 75% of water content and 1.7 of specific gravity should be reworked within 52.5 days.