Description: Fine coenocytic filaments, highly and irregularly branched.

Habitat: Endozoic in shells of molluscs and calcareous worm tubes. Midl to sublittoral.

Distribution: Probably under-recorded in the British Isles: Scotland including the Shetlands, Ireland, England and the Isle of Man. Europe: Spain, France, Norway, Faroes and Iceland. Greenland. Atlantic coast of North America: Canada. Further afield: Canary Islands, Sri Lanka, Easter Island, Maldive Islands, Samoa, Australia, Caroline Island and Marshall Islands.

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

iNaturalist: Ostreobium quekettii at iNaturalist World Species Observations database.

WoRMS: Ostreobium quekettii at World Register of Marine Species.