Description: Thallus monosiphonous, erect to 5 cms long in dense tufts. Not corticate but with loose downgrowing filaments. Branches alternate and distichous. Third order of laterals curving away from the parent latteral towards the tips.

Habitat: Epiphytic, epizoic or epilithic in low littoral and to 30 m depth.

Distribution: Generally south westerly in the British Isles. Europe: Mediterranean, Azores, Portugal, Atlantic coast of Spain and Norway. Atlantic coast of North America: Massachusetts, Rhode Island, Connecticut, New Jersey and Delaware. Further afield: Canary Islands, Morocco and Brazil.

Similar Species: P. borreri can be distinguished from Aglaothamnion by the size of the apical cell and when reproductive by its polysporangia and from Callithamnion by its corticate main axis.

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

iNaturalist: Pleonosporium borreri at iNaturalist World Species Observations database.

WoRMS: Pleonosporium borreri at World Register of Marine Species. Accepted name: Pleonosporium borreri (Smith) Nägeli, 1862. AphiaID: 144600.

Classification: Biota; Plantae; Biliphyta; Rhodophyta; Eurhodophytina; Florideophyceae; Rhodymeniophycidae; Ceramiales; Ceramiaceae; Spongoclonioideae; Spongoclonieae; Pleonosporium