Sea urchins are spiny, globe-shaped relatives of starfish. As grazers, they play a big role in shaping kelp forests and coral reefs.
Interesting facts
- Sea urchins move on hundreds of tiny tube feet as well as their spines.
- Without predators such as sea otters, urchins can multiply and destroy kelp forests.
- Northern California lost most of its kelp forests after urchin numbers exploded around 2014.
- Urchin roe, called uni, is a delicacy in Japan and elsewhere.
- Some red sea urchins may live for over 100 years.
- A mass die-off of long-spined urchins in the Caribbean in 1983 contributed to algae overgrowing coral reefs.
Behaviour
Sea urchins graze slowly over rocks and reefs, scraping algae with their teeth. Some hide in crevices by day and feed at night.
Breeding and young
Urchins release eggs and sperm into the water. Their larvae drift in the plankton for weeks before settling.
Threats and conservation
Disease, warming seas and overharvesting in some regions.
Where to see it
- Rock pools and reefs worldwide
- Kelp forests of Monterey, California
- Mediterranean coasts
- Caribbean coral reefs
Status source: IUCN Red List. Profile last reviewed September 2026.
