Green sea urchin

Green sea urchin

Scientific name: Psammechinus miliaris
This small, round sea urchin is (unsurprisingly!) green in colour and can be found on rocky shores around the UK.

Species information


Diameter: Up to 5cm Average Lifespan: 10 years

Conservation status


When to see

January to December


The Green sea urchin is a small spiny urchin that lives amongst the seaweeds on rocky shores and on the seabed down to depths of 100m. It is often found on or under kelp and on seagrass beds. It feeds by grazing on seaweed, sponges and bryozoans and will also eat barnacles, mussels and worms. Their strong short spines are often tipped with a brilliant purple, giving them their other name of Purple tipped urchin. Sea urchins are related to starfish and are a type of animal called an echinoderm, which means "spiny skinned." It is sometimes referred to as the Shore sea urchin.

How to identify

There are several similar sized sea urchins found in British waters. The Green sea urchin is slightly flattened in shape and greenish in colour, with purple tips to the spines.


Found on rocky shores all round our coasts, particularly common in the North Sea.

Did you know?

In the past, Sea urchins were referred to as Sea Hedgehogs on account of their spiny shells! They are also sometimes called "burrs" in Scotland, as they look a bit like the spiky little seed pods.

How people can help

When rockpooling, be careful to leave everything as you found it - replace any seaweed you move out of the way, put back any crabs or fish and ensure not to scrape anything off its rocky home. If you want to learn more about our rockpool life, Wildlife Trusts around the UK run rockpool safaris and offer Shoresearch training - teaching you to survey your local rocky shore. The data collected is then used to protect our coasts and seas through better management or through the designation of Marine Protected Areas. The Wildlife Trusts are working with sea users, scientists, politicians and local people towards a vision of 'Living Seas', where marine wildlife thrives. Do your bit for our Living Seas by supporting your local Wildlife Trust or checking out our Action Pages.