Starfish, or sea stars, are star-shaped echinoderms related to sea urchins and sea cucumbers. Many are important predators that keep populations of mussels and urchins in check, shaping entire coastal ecosystems.
Interesting facts
- Starfish are not fish, which is why many scientists prefer the name ‘sea stars’.
- They have no brain and no blood; seawater pumped through their bodies does many of the jobs of blood.
- Most have a simple eye at the tip of each arm.
- Many can regrow lost arms, and some can regrow a whole body from a single arm.
- They move on hundreds of tiny tube feet.
- Since 2013, a wasting disease has killed billions of sea stars along the Pacific coast of North America.
Behaviour
Starfish creep slowly along the seafloor, using their tube feet to grip rocks and pry open shells. Some species, such as the crown-of-thorns starfish, feed on coral and can damage reefs during outbreaks.
Breeding and young
Most species release eggs and sperm into the water, and larvae drift in the plankton before settling. Some can also reproduce by splitting in two.
Threats and conservation
Disease linked to warming seas, pollution, habitat loss and collection for souvenirs.
Where to see it
- Rock pools on coasts worldwide at low tide
- Olympic National Park tide pools, Washington
- Great Barrier Reef, Australia
- Never remove live starfish from the water
Status source: IUCN Red List. Profile last reviewed September 2026.
