Diazona violacea is a colonial ascidian forming massive colonies of up to 40 cm
in diameter and 20 cm in height. Young colonies are rather ball-shaped, whereas older ones are slightly
flattened. The zooids
are joined in a common gelatinous cushion-shaped base. The branchial parts of the zooids (the upper parts)
are distinct and emerge of 2 cm from the base. The test is more or less translucent, white or yellowish.
A vertical line draws the endostyle of each zooid; the atrial and oral siphons are underlined by a white
margin and six white spots ornate the upper part of the pharynx. Diazona zooids resemble clavelina ones but
their bases are different: a thick basal mass for Diazona versus a thin basal stolon for Clavelina.
At the end of summer, after reproduction time, zooids atrophy and there's only the basal mass left. In
spring-time, the colony buds again from this base.
It lives attached to rocks or stones covered by sand, in strong current-swept areas between 15 and 200 meters
deep in the Atlantic Ocean, the English Channel and the Mediterranean Sea.
(source : European Register of Marine Species)
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.
Diazona violacea
Close view.
Diazona violacea
Juvenile.
Diazona violacea
Colony.
Top photograph :
© Javier Santiago. Published with author's kind permission :
Diazona violacea,
Ria de Arosa, Galice, North-West of Spain. Depth 32 meters.
Bottom photographs : © Javier Santiago. Published with author's kind permission :
Diazona violacea, Close view.. Ria de Arose, Galicia, North-West Spain. Depth 32 meters.
© Wilfried Bay-Nouailhat. Published with author's kind permission :
Diazona violacea, Juvenile.. Illes Medes, Costa Brava, East Spain. Depth 22 meters.
© Wilfried Bay-Nouailhat. Published with author's kind permission :
Diazona violacea, Colony.. Baie de Lannion, North Brittany, West of France. Depth 28 meters.
Text : Anne Bay-Nouailhat © 2007-2018.
Translation : Anne Bay-Nouailhat © 2007-2018.
