Sea stars move using a unique water vascular system that powers hundreds of tube feet.
The Water Vascular System
Sea stars don't have muscles in the conventional sense for movement. Instead, they rely on a hydraulic system:
- Water Pressure: They use water pressure to operate their tube feet.
- Ampulla: Water is squeezed down into the tube foot. As explained in the reference YouTube video Deep Dive - How Do Starfish Move, water is squeezed down into the tube foot, causing it to extend.
- Tube Feet: These extend and retract, allowing the sea star to move. The reference states that to retract the tube foot, the ampulla relaxes.
The Process of Movement
Here's a breakdown of how the water vascular system enables movement:
- Water is drawn into the system through a sieve plate called the madreporite.
- The water is then circulated through canals to the ampullae.
- The ampullae contract, forcing water into the tube feet.
- The tube feet extend and attach to surfaces using a suction cup.
- To move, the tube feet coordinate their movements, pulling the sea star along.
- To retract, the ampulla relaxes.
Key Components in Sea Star Locomotion
| Component | Function |
|---|---|
| Tube feet | Act as suction cups for movement |
| Ampullae | Squeeze water into and out of tube feet |
| Water Pressure | Powers the extension and retraction of feet |
