Description: Minute parasite, up to 1 mm in diameter growing as a small sphere, pinkish in colour, on the frond of Gracilaria gracilis.

Habitat: Parasitic. Lower littoral and sublittoral to 16 m.

Distribution: South-western shores of the British Isles: Cos Galway, Down and Wexford in Ireland; Wales; England from Sussex and Norfolk and from the Isle of Man. Europe: Spain and France.

Similar Species: Similar to the reproductive organs, cystocarps, of Gracilaria but pale in colour.

Key Identification Features:

• Minute parasite on Gracilaria.

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

iNaturalist: Holmsella pachyderma at iNaturalist World Species Observations database.

WoRMS: Holmsella pachyderma at World Register of Marine Species. Accepted name: Holmsella pachyderma (Reinsch) Sturch, 1926. AphiaID: 145709.

Classification: Biota; Plantae; Biliphyta; Rhodophyta; Rhodophyta incertae sedis; Pterocladiophilaceae; Holmsella