Description: Growing to 40 cms from a discoid holdfast with hollow main axis up to 4 mm diameter. Irregularly branched. Soft and gelatinous.

Habitat: Rare. Epilithic in the upper sublittoral into the sublittoral to 5 m.

Distribution: Generally on the south-western shores of the British Isles: western Ireland, Wales, south-west England, the Shetlands and the Channel Islands. Europe: Portugal and Atlantic coast of Spain. Further afield: Canary Islands.

Similar Species: Nemalion helminthoides is usually simple or with few branches unlike Helminthocladia calvadocii.

Key Identification Features:

• Gelatinous with a hollow main axis in mature plants.

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

iNaturalist: Helminthocladia calvadosii at iNaturalist World Species Observations database.

WoRMS: Helminthocladia calvadosii at World Register of Marine Species.