Description: A distinctive sponge, which can be recognised in situ. Forms small patches of 3–5 cm in diameter, often with several patches adjacent to one another; each patch bears one or two oscules. The oscules are combined with inhalent pore sieves at the tip of inflated papillae, which project from the sediment that the sponge is frequently covered in. The colour of the sponge is bright yellow, sometimes with

darker yellow or orange lines radiating from the papillae. It turns a dark brown/black in alcohol.

Habitat: Mostly found in deeper water, below 30 metres, but occasionally as shallow as 20m. Tolerant of silt, occurs on vertical or overhanging bedrock in semi-exposed, tide swept locations.

Distribution: In Northern Ireland this species occurs at Rathlin Island and The Maidens (Larne). It has also been recorded fro St John's Point, Co Donegal and SW Scotland.

Similar Species: This species is unlikely to be confused with other sponges.

Key Identification Features:

• • Oscules combined with inhalent pore sieves at the tip of inflated papillae
  Small patches, bright yellow in colour

iNaturalist: Hymedesmia rathlinia at iNaturalist World Species Observations database.

GBIF data for Hymedesmia (Hymedesmia) rathlinia

WoRMS: Hymedesmia rathlinia at World Register of Marine Species. Accepted name: Hymedesmia (Hymedesmia) rathlinia Goodwin & Picton, 2009. AphiaID: 416422.

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