Botryllus schlosseri (Pallas, 1766)

Star sea squirt

Botryllus schlosseri

Concarneau Bay, France, 9 meters, 2011, WBN

Botryllus schlosseri

Pointe de Trévignon, France, 8 meters, 2011, WBN

Botryllus schlosseri

Pointe de Trévignon, France, 8 meters, 2011, WBN

Botryllus schlosseri

Bay of Lannion, France, 10 meters, 2011, WBN

Botryllus schlosseri

Camaret, France, 9 meters, 2011, WBN


Botryllus schlosseri is a colonial ascidian forming encrusting flattened colonies of 4 to 5 cm in diameter. The zooids are gathered in systems of 3 to 12 individuals around a common atrial siphon. These systems look like stars dispatched through the colony within a common test.The siphons do not protude but form numerous little holes opening and closing according to the colony activity. The star tunicate has various colours: yellow, blue, brown-yellowish, green, mauve, reddish. The colour of the zooid is distinct from the colour of the common test. Colonies encrusted rocks, seaweeds and even other ascidians.


Botryllus schlosseri is found from low level water to 10 meters deep in the Atlantic Ocean, the North Sea, the English Channel and the Mediterranean Sea.

Image satellite: © Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS, AeroGRID, IGN, and the GIS User Community.

Données de distribution : Botryllus schlosseri (Pallas, 1766) in GBIF Secretariat (2019). GBIF Backbone Taxonomy. Checklist dataset accessed via on 2022-05-23.


Source : World Register of Marine Species

Biota (Superdomain)
Animalia (Kingdom)
Chordata (Phylum)
Tunicata (Subphylum)
Ascidiacea (Class)
Stolidobranchia (Order)
Styelidae (Family)
Botryllus (Genus)
Botryllus schlosseri (Species)

Page glossary

Zooid : individual, single animal.

Test : or tunic: thick layer secreted by the mantel containing cellulose and protecting the animal.

Atrial siphon : opening through which water is expelled.


Text : Anne Bay-Nouailhat © 2005 - 2022.

Photos : © Wilfried Bay-Nouailhat. Published with his kind permission.
Websites and reference works : Consult bibliography

How to cite this page

Bay-Nouailhat A., January 2005, Description of Botryllus schlosseri, [On line], consulted on 2022 May 23.


Photographie de Anne Bay-Nouailhat

Anne Bay-Nouailhat

Project manager in marine environment
Professional diver - Naturalist

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