Starfish are living animals. They are members of the echinoderm family – ‘echino’ meaning spiny and ‘derm’ meaning skin. They are classed along with sea urchins. While they may look like they never move, starfish are actually constantly on the go. On the underside of its body a starfish is covered in tiny tentacles. These are called tube feet, and propel the starfish along.
The muscles in these tube feet contract and relax to grip surfaces. Each individual foot shoots outwards and forwards from the body and grips the closest surface. When the foot contracts and relaxes it creates a vacuum. This is what helps a starfish cling to surfaces.
Some starfish can move up to 50 millimetres (two inches) per second. Sunflower sea stars are some of the fastest in the world, look at this one go!
That may not look fast, but when you see starfish movement sped up it’s obvious how efficient movers they really are. Here are some horned starfish bumping into each other at rush hour.
Image from flickr.com/photos/photeka