Star ascidian

Star ascidian

Star ascidian by Wembury Marine Centre

Star ascidian

Scientific name: Botryllus schloserri
One of the most eye-catching sights on the rocky shore, this mind-boggling species resembling a collection of beautiful pressed flowers is actually a colony of individual animals!

Species information


Colonies can reach 10-20cm across

Conservation status


When to see



This colony of sea squirts looks like a bunch of beautiful flower petals stuck next to each other to form a mosaic of stars. It takes 3-12 individuals to produce one of the star-shaped patterns. You will usually find these colonies on the underside of rocks in rockpools or sometimes on kelp fronds.

How to identify

Star ascidian have a dark, flat, gelatinous structure (tunic) with petal/star patterning covering the tunic. They often vary in colour from clear to yellow to light brown stars.


Found all around Britain and Ireland

Did you know?

Individual star ascidians have their own intake siphon to allow nutrients and oxygen to flow into their cells, but they share an outflow opening in the centre of the star!

How people can help

Always follow the Seashore Code when rockpooling, be careful to leave everything as you found it - replace any rocks you turn over, 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.