Description: Thalli erect arising from a discoid holdfast, hollow and cylindrical, unevenly inflated to 40 cms long and 2 cms wide.

Habitat: Common. Epiphytic on other algae in lower rock pools and the sublittoral to 18 m.

Distribution: Widely distributed around the British Isles. Europe: Atlantic coast of Spain and France, Belgium, Netherlands, Denmark, the Baltic, Norway, Sweden, Faroes and Iceland. Atlantic coast of North America: Canada, Maine, New Hampshire, Massachusetts, Rhode Island, Connecticut, Long Island and Virginia. Further afield: the Canary Islands.

Similar Species: Other species of Asperococcus are similar. A. compressus is flattened, A. bulbosus is inflated. A. scaber is solid, not hollow and less than 13 mm long.

Key Identification Features:

• Dotted all over with sori of colourless hairs and sori.

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

iNaturalist: Asperococcus fistulosus at iNaturalist World Species Observations database.

WoRMS: Asperococcus fistulosus at World Register of Marine Species. Accepted name: Asperococcus fistulosus (Hudson) W.J.Hooker, 1833. AphiaID: 145313.

Classification: Biota; Chromista; Harosa; Heterokonta; Ochrophyta; Phaeophyceae; Fucophycidae; Ectocarpales; Chordariaceae; Asperococcus