Tube feet

Tube feet are small, extensible appendages of echinoderms operated by the water vascular system. They enable attachment, movement, feeding, and sensing.

Water vascular system: A fluid-filled hydraulic network in echinoderms that powers tube feet and other functions. Its canals deliver the fluid pressure that operates tube feet.
Sea star locomotion: Movement by sea stars through coordinated attachment and release of their tube feet. Sea stars use repeated tube-foot cycles to travel across surfaces.
Echinoderm: A marine invertebrate in the phylum Echinodermata, including sea stars, brittle stars, and sea urchins. Tube feet are a distinctive appendage found across this animal phylum.
Aristotle's lantern: The complex jaw apparatus used by many sea urchins to scrape or bite food. It handles food mechanically, unlike tube feet, which mainly grip and manipulate it.
Ampulla: A muscular bulb connected to an echinoderm tube foot that helps drive its extension. Contraction of this bulb pushes fluid into the tube foot.
Echinoderm feeding: The varied ways echinoderms capture, handle, and ingest food. Tube feet can manipulate prey and transport food toward the mouth.
Radial symmetry: A body organization in which structures are arranged around a central axis. In many adult echinoderms, tube feet are arranged in repeated radial series.
Brittle star locomotion: Movement in brittle stars driven mainly by coordinated motions of their arms. Brittle stars rely more on arm rowing than tube-foot stepping.
Suction: A pressure difference that pulls surfaces together across a seal. In some echinoderms, tube-foot tips attach by creating suction against a surface.
Bivalve predation by sea stars: Predation in which a sea star pulls apart a bivalve's shell and everts its stomach into the opening. Tube feet provide the sustained grip used to pry open bivalve shells.

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