Description: Microscopic. Filaments growing on or within the surface of the host with short erect external filaments.

Habitat: Very rare. On fronds of Dictyota and Desmarestia.

Distribution: Recorded only from a few sites in Ireland and the south coast of England. Europe: Mediterranean, Atlantic coasts of Spain and France, the Netherlands. Atlantic coast of North America: North Carolina.

Similar Species: Many other small tufted algae are similar, all require microscopic examination for identification.

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

iNaturalist: Herponema solitarium at iNaturalist World Species Observations database.

WoRMS: Herponema solitarium at World Register of Marine Species.