Description: Microscopic uniseriate filaments, unbranched, living entirely within the host species.

Habitat: Very rare. Growing endophytically in Himanthalia elongata.

Distribution: Known only from St Mary's Island, Whitbay, Northumberland, NE England and Garheugh Port, North Solway, SW Scotland.

Similar Species: All species of Acrochaetium are similar, microscopic examination is required for identification.

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

iNaturalist: Acrochaetium sanctae-mariae at iNaturalist World Species Observations database.

WoRMS: Acrochaetium sanctae-mariae at World Register of Marine Species. Accepted name: Acrochaetium sanctae-mariae (Darbishire) Hamel, 1927. AphiaID: 144385.

Classification: Biota; Plantae; Biliphyta; Rhodophyta; Eurhodophytina; Florideophyceae; Nemaliophycidae; Acrochaetiales; Acrochaetiaceae; Acrochaetium