Lightbulb sea squirt

Lightbulb sea squirt

Lightbulb sea squirt ©Polly Whyte/Earth in Focus

Lightbulb sea squirt

Scientific name: Clavelina lepadiformis
The lightbulb sea squirt is common around much of the UK. Its easy to see where its name came from!

Species information


Height: Up to 4cm tall

Conservation status


When to see

January to December


Sea Squirts are an interesting bunch! As adults, they live permanently attached to rocks under the sea and are pretty simple animals. However, before settling down, they start life as a tadpole-like larvae. Once they find a suitable spot to settle, they start by digesting their own brain, tail and spine-like structure called a notochord, before metamorphosising into adults! Adult sea squirts are a barrel-shaped animal with 2 holes at the top end - each is a siphon, one for taking water in and one for pushing water out. Their simple sac-like bodies are covered by a protective layer called a tunic - this is where they get their other name, Tunicates, from. Sea squirts are filter feeders and take in seawater using one siphon (inhalent), from which they filter out plankton and detritus; expelling the wastewater from the other siphon (exhalent). There are many different types of sea squirt found in UK seas, some live alone but many live in colonies. The lightbulb sea squirt is colonial and common around much of the UK, found living on rocks and bounders down to depths of 50m. It is also often found living in harbours and marinas. They get their name as they really do look a lot like a lightbulb! They have a transparent tunic and a creamy-white line along their length and forming a ring on top.

How to identify

Lightbulb sea squirts look like a clump of lightbulbs growing on a rock - with their transparent tunics and a creamy-white line along their length and forming a ring on top.


Found around much of the UK, absent in the Bristol Channel, between Colwyn Bay and Morecambe Bay, between the Firth of Forth and Tynemouth and between the Humber Estuary and Dover.

Did you know?

Sea Squirts get their name from their tendency to shoot out a stream of water when removed from the sea.

How people can help

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.