Diplosoma spongiforme is an encrusting colonial ascidian which can cover
rock surfaces of 20 to 30 cm in diameter. Several colonies can join together and can thus cover a surface
of several square meters. Zooids are immersed in a common gelatinous test. Its thickness is irregular, up to
6 mm , giving to its surface an embossed aspect. The oral siphons of the zooids constitute tiny openings densely
distributed all other the colony. Several zooids are gathered around a common, broad and slightly prominent
atrial siphon, forming a system. Several systems occur in the colony making it resemble a sponge. The
jelly-synascidian has a white translucent test with greenish or yellowish mottlings. The margin of the siphons
may be white or bluish.
It is present from surface to 40 m deep in the Atlantic Ocean, the English channel, the North Sea and the
Mediterranean Sea.
Phylum Chordata, subphylum Tunicata, class Ascidiacea, order Aplousobranchia, family Didemnidae, Diplosoma spongiforme (Giard, 1872).
Zooid: Individual, single animal.
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.
Photograph: © Wilfried Bay-Nouailhat. Published by the author's permission.
Diplosoma spongiforme, Iles Glénan, South-Brittany, West of France. Depth 6 meters.
Text: Anne Bay-Nouailhat © 2006-2008.
Translation: Anne Bay-Nouailhat © 2007-2008.
