Grades K–2 · Organisms
How can a sea star walk on tiny tube feet?
A sea star seems to glide over a rock. Under its arms are many tiny tube feet. These soft feet do the moving, even though the sea star has no legs like ours.
In the diagramWater pressure helps tiny feet reach▸ Sea starMany feet work togetherWater-filled bulbTube footRockSticky tipThe feet lie under the arms.
Each foot connects to a small water-filled bulb inside the body. Muscles squeeze the bulb. Water moves into the foot and pushes it longer. The foot can reach the rock.
The tip makes a sticky material that helps it hold on. The foot later lets go and pulls back. Many feet work together as the sea star creeps along.
About this explanation
Starting knowledge: Understands that pushing water into a soft tube can change its shape.
Sources
- Smithsonian Institution — Sea Stars, Urchins, and Relatives
- Lengerer and colleagues, Beilstein Journal of Nanotechnology — The structural and chemical basis of temporary adhesion in the sea star Asterina gibbosa