Editing Echinoderm (section)

===Locomotion===
[[File:Podia de Colobocentrotus atratus.JPG|thumb|Echinoderms use their tube feet to move about. (''[[Colobocentrotus atratus]]'' shown)]]
{{further|Animal locomotion}}

Echinoderms primarily use their tube feet to move about, though some sea urchins also use their spines. The tube feet typically have a tip shaped like a suction pad in which a vacuum can be created by contraction of muscles. This combines with some stickiness from the secretion of [[mucus]] to provide adhesion. The tube feet contract and relax in waves which move along the adherent surface, and the animal moves slowly along.<ref name="Smith">{{harvnb|Smith|1937}}</ref>

Brittle stars are the most agile of the echinoderms. Any one of the arms can form the axis of symmetry, pointing either forwards or back. The animal then moves in a co-ordinated way, propelled by the other four arms. During locomotion, the propelling arms can made either snake-like or rowing movements.<ref name="Astley 2012">{{harvnb|Astley|2012}}</ref> Starfish move using their tube feet, keeping their arms almost still, including in genera like ''[[Pycnopodia]]'' where the arms are flexible. The oral surface is covered with thousands of tube feet which move out of time with each other, but not in a [[metachronal rhythm]]; in some way, however, the tube feet are coordinated, as the animal glides steadily along.<ref>{{harvnb|Brusca|Moore|Shuster|2016|pp=982–983}}</ref> Some burrowing starfish have points rather than suckers on their tube feet and they are able to "glide" across the seabed at a faster rate.<ref>{{harvnb|Sea Stars of the Pacific Northwest|loc=Sand Star – ''Luidia foliolata''}}</ref>

Sea urchins use their tube feet to move around in a similar way to starfish. Some also use their articulated spines to push or lever themselves along or lift their oral surfaces off the substrate. If a sea urchin is overturned, it can extend its tube feet in one ambulacral area far enough to bring them within reach of the substrate and then successively attach feet from the adjoining area until it is righted. Some species bore into rock, usually by grinding away at the surface with their mouthparts.<ref>{{harvnb|Ruppert|Fox|Barnes|2004|pp=899–900}}</ref>

[[File:Neothyonidium magnum (Burrowing sea cucumber).jpg|thumb|Sea cucumbers like this ''Neothyonidium magnum'' can burrow using peristaltic movements.]]

Most sea cucumber species move on the surface of the seabed or burrow through sand or mud using [[peristalsis|peristaltic]] movements; some have short tube feet on their under surface with which they can creep along in the manner of a starfish. Some species drag themselves along using their buccal tentacles, while others manage to swim with peristaltic movements or rhythmic flexing. Many live in cracks, hollows and burrows and hardly move at all. Some deep-water species are [[pelagic]] and can float in the water with webbed papillae forming sails or fins.<ref>{{harvnb|Ruppert|Fox|Barnes|2004|pp=911–912}}</ref>

The majority of feather stars (also called Comatulida or "unstalked crinoids") and some stalked forms are motile. Several stalked crinoid species are sessile, attached permanently to the substratum. Movement in most sea lilies is limited to bending (their stems can bend) and rolling and unrolling their arms; a few species can relocate themselves on the seabed by crawling. Feather stars are unattached and usually live in crevices, under corals or inside sponges with their arms the only visible part. Some feather stars emerge at night and perch themselves on nearby eminences to better exploit food-bearing currents. Many species can "walk" across the seabed, raising their body with the help of their arms, or swim using their arms. Most species of feather stars, however, are largely sedentary, seldom moving far from their chosen place of concealment.<ref name="Feeding">{{harvnb|Messing|2006}}</ref>