Description: Very small branched uniseriate filaments, microscopic. Most branches only of a single cell.

Habitat: Rare. Epiphytic on algae in the sublittoral to 7 m depth.

Distribution: Widely scattered sites around Britain from Orkney, the Shetlands and Cos Cornwall and Devon. Galway Bay and the Aran Islands in Ireland. Europe: Mediterranean,Atlantic coast of France, Norway and Iceland. Greenland. Atlantic coast of North America: Canada and North Carolina. Further afield: Canary Islands.

Similar Species: All species of Acrochaetium are very similar. Microscopic examination is required for identification.

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

iNaturalist: Acrochaetium parvulum at iNaturalist World Species Observations database.

WoRMS: Acrochaetium parvulum at World Register of Marine Species.