tube foot

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun One of the numerous external, fluid-filled muscular tubes of an echinoderm, such as a starfish or sea urchin, serving as organs of locomotion, food handling, and respiration.

from The Century Dictionary.

• noun One of the numerous tubular locomotory pedicels of the ambulacra of echinoderms, as star-fishes and sea-urchins; a water-foot.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A locomotor appendage of an echinoderm consisting of a tube with longitudinal muscles, pressurized by water.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun tentacular tubular process of most echinoderms (starfish and sea urchins and holothurians) having a sucker at the end and used for e.g. locomotion and respiration