Gas exchange
Aquatic respiration is the process whereby an aquatic organism exchanges respiratory gases with water, obtaining oxygen from oxygen dissolved in water and excreting carbon dioxide. The gills of Sabellastarte magnifica, the feather duster worm, are its featherlike radioles (ciliated tentacles). On each radiole, many small appendages called pinnules. These are filled with blood and covered with beating cilia, which draw water through the fan for feeding and respiration.
