Styela clava is a solitary ascidian of up to 12 cm high. It is club-shaped
erected from a narrow stalk attached to the sustratum. The stalk size may be a third of the overall ascidian.
The test is firm, leathery and wrinkled. Its colour is brown with white mottlings. Sometimes, algae or
some invertebrates may fix and grow on it. The terminal siphons are close to each other. It lives in
shallow water where water is warmer, in harbours, on piles, hulls or rocks and stones.
This species first appeared in the English Channel, in Plymouth in 1953 and quickly spread through the
North Sea, the Baltic Sea and through the Atlantic Ocean toward Spain. Originated from North-Western Pacific,
Japan and Korea, it was probably introduced in Europe during the Korean War attached to battleship-hulls.
Since 1981, it was also described on the other side of the Atlantic.
Phylum Chordata, subphylum Tunicata, class Ascidiacea, order Stolidobranchia, family Styelidae, Styela clava(Herdman, 1881).
Test: or tunic: thick layer secreted by the mantel containing cellulose and protecting the animal.
Photograph: © Wilfried Bay-Nouailhat. Published with author's kind permission.
Styela clava, Baie de Concarneau, South-Brittany, West of France. Depth 6 meters.
Text: Anne Bay-Nouailhat © 2006-2008.
Translation: Anne Bay-Nouailhat © 2007-2008.
