Polymastia boletiformis is a sponge forming a smooth, hemispherical cushion base reaching
up to 10 cm in diameter. Many tube-shaped outgrowths, slightly conical and between 2 to 10 cm in height,
emerge from the base and are ending with the oscules. Its colour is uniform but may vary : yellow, orange, ochre, gray or greenish.
It is found from surface to depths down to 40 meters, in the Atlantic Ocean, the North Sea and the
English Channel.
There are other sponges of the genus Polymastia in the same geographical
area. They all possess a basal cushion with erected processes. Nevertheless, they are quite easily
distinguishable:
Polymastia mamillaris is clearer, with a dirty yellow colour. The base is often covered with sand and
the tubules are flattened, translucide and clearer than the base.
Polymastia gleneni (Aaptos papillata) is pale pink to purplish pink. The processes are paler,
cylindrical and tip-rounded. The base is often covered with sand.
(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 :
Polymastia boletiformis,
Ria d'Etel, South-Brittany, West of France. Depth 12 meters.
Text : Wilfried Bay-Nouailhat © 2004-2017.
Translation : Anne Bay-Nouailhat © 2007-2017.
