Ciona intestinalis (Linnaeus, 1767)

Yellow-ringed sea squirt

Ciona intestinalis

Concarneau Bay, France, 5 meters, 2011, WBN

Ciona intestinalis

Concarneau Bay, France, 4 meters, 2011, WBN

Ciona intestinalis

Concarneau Bay, France, 4 meters, 2011, WBN

Ciona intestinalis

Concarneau Bay, France, 11 meters, 2011, WBN


Ciona intestinalis is a solitary ascidian which is up to 15 cm high. This upright cylindrical sea-squirt has a smooth soft test. It is translucent and its colour varies from white to yellow. Muscular bands, branchial sac and intestine are visible through the test. The edges of the siphons have a yellow margin. Oral and atrial siphons are contiguous and terminal. The oral siphon has 8 lobes and the atrial one has 6 lobes. Yellow sea-squirts often live in groups attached to rocks, piles, hulls. It can be common in harbours because this species seems to bear polluted waters.


Ciona intestinalis is found from low water level to 50 m deep in the Atlantic Ocean, the English Channel, the North Sea, the Baltic sea 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 : Ciona intestinalis (Linnaeus, 1767) 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)
Phlebobranchia (Order)
Cionidae (Family)
Ciona (Genus)
Ciona intestinalis (Species)

Page glossary

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

Oral siphon : opening by which water is drawn in the ascidian.

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., October 2005, Description of Ciona intestinalis, [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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