Pachymatisma johnstonia is a massive sponge which may reach 40 cm in diameter and 10 cm in
height. It has rounded margins and elongate lobes with a very smooth surface. Oscules are gathered in linear groups
on the top of the lobes. Colour varies from greish white to dark purplish grey. It has a firm rubbery
consistency.
It is attached to rocks, from swallow waters to depths up to 300 meters, in the English Channel, the Atlantic ocean
from the North of the British Isles down to Spain and in the Mediterranean Sea.
(source: European Register of Marine Species)
Oscule : Opening generally quite visible, through which sponges expel water they have filtered to extract food particles.
Top photograph :
© Wilfried Bay-Nouailhat. Published with author's kind permission :
Pachymatisma johnstonia,
Ile de Groix, South-Brittany, West of France. Depth 28 meters.
Text : Wilfried Bay-Nouailhat © 2006-2010.
Translation : Anne Bay-Nouailhat © 2007-2010.
