Description: This sponge grows as a thin sheet or cushion in patches 10-15cm across. It is normally pale orange/pink in colour but occasionally it is bright red. The surface is covered in shallow, circular, non-contractile depressions of varying diameters. The rims of these depressions are usually lighter coloured than the rest of the body. The depressions contain the inhalant pores, and are covered by a fine, gauze-like mesh.

Habitat: A common species in areas with silt free, infralittoral bedrock and boulders. Apparently not found in harbours.

Distribution: Recently known from scattered localities all around the British Isles, but currently not recorded from North Sea coasts.

Similar Species: Provided the colour is pale orange-pink and the rims of the depressions are of a lighter colour, the identification stands a good chance of being correct, but in case of doubt microscopic examination is essential. Several other genera contain species which have depressions with rims which are the same colour as the general surface (see e.g. Phorbas fictitius and Hymedesmia pauperatus.

Key Identification Features:

• Pale orange/pink thin sheet to cushion.
• Shallow, circular depressions on surface with lighter coloured rims.

Distribution Map from NBN: Hemimycale columella at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Hemimycale columella at iNaturalist World Species Observations database.

WoRMS: Hemimycale columella at World Register of Marine Species. Accepted name: Hemimycale columella (Bowerbank, 1874). AphiaID: 133543.

Classification: Biota; Animalia; Porifera; Demospongiae; Heteroscleromorpha; Poecilosclerida; Hymedesmiidae; Hemimycale