Definition of tube feet
Tube feet are the many small tubular projections found most famously on the oral face of a sea star's arms, but are characteristic of the water vascular system of the echinoderm phylum which also includes sea urchins, sand dollars, sea cucumbers, and many other sea creatures.
Examples of tube feet in the following topics:
- Sea stars use their tube feet not only for gripping surfaces, but also for grasping prey.
- Small organic particles are moved into the mouth by the tube feet.
- These echinoderms do not have arms, but are hemispherical or flattened with five rows of tube feet that help them in slow movement; tube feet are extruded through pores of a continuous internal shell called a test.
- In these urchins, the upper surface of the body is slightly domed, but the underside is flat, while the sides are devoid of tube feet.
- Sea cucumbers of class Holothuroidea are extended in the oral-aboral axis and have five rows of tube feet .
- In echinoderms such as sea stars, every arm bears two rows of tube feet on the oral side which help in attachment to the substratum.
- The water vascular system also projects from holes in the skeleton in the form of tube feet.
- These tube feet can expand or contract based on the volume of water (hydrostatic pressure) present in the system of that arm.
- The ring canal connects the radial canals (there are five in a pentaradial animal), and the radial canals move water into the ampullae, which have tube feet through which the water moves.