PERCEPTION AND SELECTION OF MACROPHYTE DETRITAL FALLS BY THE BATHYAL ECHINOID STYLOCIDARIS-LINEATA

Many deep-sea animals are known to exploit patchy food resources such as animal carcasses and sunken plant remains, but the mechanisms by wh ich such foods are located remain generally unknown. The bathyal echin oid Stylocidaris lineata is an omnivorous deposit feeder that ingests sediment, dead animal remains, seagrass blades, and macroalgae such as Sargassum spp. Using a submersible, we investigated the ability of ur chins to locate and exploit large falls of detritus. Individuals quick ly arrived at packets of Thalassia testudinum and Sargassum spp. place d on the bottom, and they preferred these food items significantly ove r inert controls. However, the echinoids demonstrated no significant t endency to move toward the scent of upstream T. testudinum, either in situ or in laboratory flume experiments. Individuals moved at net spee ds up to 30 m day-1. The existing evidence suggests that S. lineata lo cate food by chance encounter, not distant chemoreception.