What is Tube feet?
[[File:Starfish_(1).jpg|thumb|right|300px|Closeup of the tube feet of a live starfish]] '''Tube feet''' are small tube-like projections on the underside ([[oral]] side) of [[echinoderms]]. They are part of the water vascular system of echinoderms. Tube feet are used to move, feed and [[respiration|breathe]]. They are arranged in grooves along the arms. They operate through [[hydraulics|hydraulic pressure]]. They are used to pass food to the oral mouth at the center, and can attach to surfaces. Tube feet allow these animals to stick to the ocean floor and move slowly. A sea star that is overturned simply turns one arm over and attaches it to a solid surface, and levers itself the right way up. Tube feet are used by [[starfish]] are used to open up [[bivalve]] shells. The shells of [[brachiopods]] and bivalves are held together by strong muscles. What the starfish does is clamp hold of them on either side with its tube feet, and apply a steady pull. The starfish, with its muscles and [[hydraulic]] system, can pull for much longer than any bivalve muscle can withstand. Apparently, ten minutes are usually enough to open the shell a bit. Then the starfish slips its stomach inside the shell. The stomach can get through a slot as narrow as 0.1mm.<ref>Vermeij G.J. 1987. ''Evolution and escalation: an ecological history of life''. Princeton N.J. p153</ref> The starfish then dissolves the [[mollusc]] where it lives, absorbing the [[nutrient]]s. This digestion process takes much longer than opening the shell, perhaps a couple of days.<ref>Jangoux M. and Lawrence J.M. (eds) 1982. ''Echinoderm nutrition''. Balkema, Rotterdam.</ref> == References == {{reflist}} [[Category:Echinoderms]] [[Category:Animal anatomy]]