ABSTRACT

Ophiuroldea are dominant epifaunal elements of the shelves and slopes of the Greeeland-Iceland-Norwegian Seas. Because of their abundance as well as feeding and locomotory activity they are supposed to contribute significantly to particle and nutrient transport through the sediment surface and within the benthic boundary layer. Several brittle star species are able to exhibit various feeding habits. Species of the genus Ophiura have been described to feed as predators, scavengers or deposit feeders. Analysis of stomach contents, however, usually provide only information restricted to an instant of time. Little is known about the impact of variations in food supply and abiotic factors such as current velocities on the feeding behaviour.

Small specimens (disc diameter: 3–4 mm) of Ophiura sp. from the western Barents Sea were sampled with a Van Veen grab. In addition, Ophiopholis aculeata, Ophiacantha sp. and Amphiuridae were observed in the samples. Bottom video imaging indicated that bottom currents can reach high velocities but may also vary considerably.

Several specimens of Ophiura sp. were observed by time-lapse video in aquaria and in a recirculating flume and provided with different kinds of food. A flume experiment at low flow velocities (2–5 cm/s) showed a correlation between flow conditions and animal activity. The addition of an artificial food suspension caused a further increase of activity. In a second experiment a suspension of protein-coated fluoreszent latex beads was added to the flume at low flow velocity (2cm/s). Beads could be detected in stomach contents, but no significant correlation with the bead composition of suspended matter or sediment could be seen.

In conclusion, small specimens of Ophiura sp. from the western Barents Sea feed on baits, but particles of various food suspensions could also be detected in stomach contents. There is some evidence that Ophiura sp. responds to changes in flow velocity and addition of suspended food with increased activity. However, the origin of artifical particles (suspension or sediment) detected in stomach contents after an experiment at low flow velocity remains unclear. Observations at higher current velocities are necessary to evaluate the actual importance of variability in flow regime for the feeding behaviour of this species.