Filter-feeding behavior of three Asian Hediste species (Polychaeta: Nereididae)

Abstract

The three Hediste species H. japonica, H. diadroma and H. atoka (Polychaeta: Nereididae) live in burrows in estuarine intertidal flats in eastern Asia and have been regarded as surface deposit feeders. Their filter-feeding behavior was investigated in laboratory experiments where the worms were placed in a U-shaped glass tube. The behavior is basically the same among the three species and the same as that previously observed in H. diversicolor inhabiting Atlantic coasts and consists of the following four steps: (1) Moving up to the end of the tube; (2) retreating slowly down, with the anterior body expanded laterally and moving from side to side in semicircles, making a transparent, funnel-shaped mucous net; (3) orientation of the head at 2.5–6.0 cm below the end of the glass tube, and pumping water through the net by means of active undulating movements of the body for 1–5 min; (4) moving forward and swallowing the mucous net together with the trapped particles. This behavior is accelerated by adding organic particles to the seawater. Such facultative filter feeding is judged as a unique generic characteristic of Hediste among the Nereididae and its ecological significance is discussed in relation to their estuarine habitats.