Yes, starfish (also called sea stars) really do move, even though they have no legs, no central brain, and no blood like ours. They glide across the seafloor using seawater and hundreds of tiny “feet.” Here’s how it works:
- They move, just slowly. A starfish isn’t stuck in one place. It can creep in any direction and even climb a steep rock. Most of the time it moves so slowly you’d barely catch it in the act, but it’s definitely going somewhere.
- The engine is a water vascular system. Instead of pumping blood, a starfish runs on seawater. Water comes in through a small sieve-like plate on its top side called the madreporite, then flows through internal canals: a stone canal that leads to a ring canal around the mouth, and a radial canal running down each arm. Picture a set of water pipes plumbed into the body.
- Hundreds of tube feet do the walking. Underneath each arm are rows of small, hollow “tube feet,” known as podia. A single starfish can have hundreds, sometimes thousands of them. Each one is like a miniature water balloon attached to a tiny squeeze-bulb called an ampulla.
- Water pressure powers each step. Squeeze the ampulla and water pushes into the tube foot, so it stretches out and touches the ground. Squeeze the muscles in the foot and the water flows back, so the foot pulls in. Now repeat that across hundreds of feet at once, and the whole animal slides forward.
- They hold on with glue, not suction. Most people assume the tube feet work like little suction cups. Newer research points to something else: the tip secretes a sticky chemical that bonds to the surface, then releases it to let go. The feet grab and release in a rolling wave, one patch sticking down while another lets go, which keeps the motion smooth.
- No brain, still coordinated. A starfish has no central brain handing out orders. Each tube foot senses and reacts on its own, and neighboring feet nudge each other into step, so organized movement just emerges on its own. If one arm picks up the scent of food, that arm can take the lead and steer the whole body toward it.
- Some can even gallop. Most of the time a starfish just glides along. But when it’s chasing food or escaping danger, certain species shift into a faster, bouncing “gallop,” stiffening their tube feet to vault the body forward. It’s no sprint, but it’s a real change of pace.
- Why it matters. The same tube-feet system does far more than walking. It lets a starfish hang onto wave-battered rocks, pull open the shells of clams and mussels for a meal, and flip itself back over when it lands upside down. One water-powered design handles all of it.
References
- Starfish – Wikipedia
- Water vascular system – Wikipedia
- Sea star – Encyclopaedia Britannica
- Ever Seen a Starfish Gallop? – KQED Science
Explore More
- How does a starfish use its tube feet to pry open a clam or a mussel?
- How can a starfish move and hunt without a brain or a central nervous system?
- What is the madreporite, and what would happen if it got blocked?
- How does a starfish regrow a lost arm, and can the arm grow a whole new body?
- Which sea stars are the fastest, and why might galloping have evolved?