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.
It is found from low level water to 10 meters deep in the Atlantic Ocean, the North Sea, the English Channel and the
Mediterranean Sea.
Phylum Chordata, subphylum Tunicata, class Ascidiacea, order Stolidobranchia, family Styelidae, Botryllus schlosseri (Pallas, 1766).
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.
Photograph: © Wilfried Bay-Nouailhat. Published with author's kind permission.
Botryllus schlosseri, Bay of concarneau, South-Brittany, West of France. Depth 6 meters.
Text: Anne Bay-Nouailhat © 2005-2008.
Translation: Anne Bay-Nouailhat © 2007-2008.
