Description: Thallus to 30 cms long, axes cylindrical and branched. The branches bear swolen bases (tophules) where they join the main axis. These tophules remain even after the lateral branches have been shed. Aerocysts, dilations of the branches may, or may not, occur. Slightly iridescent.

Habitat: Uncommon. Epilithic, usually sublittoral but occasionally in low littoral rock pools.

Distribution: South-western in the British Isles. Ireland generally recorded from the west and south, England from the south-west, some records from Wales and western Scotland. Europe: Gibraltar, Portugal and Atlantic coasts of Spain and France. Further afield: Canary Islands, Morocco, Mauritania, Cape Verde Islands and Senegal.

Similar Species: Other species of the genus Cystoseira.

Key Identification Features:

• Slightly iridescent underwater. Forming tophules, the swollen bases of latteral branches, may remain after the branches have been shed.

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

iNaturalist: Cystoseira nodicaulis at iNaturalist World Species Observations database.

WoRMS: Cystoseira nodicaulis at World Register of Marine Species. Accepted name: Treptacantha nodicaulis (Withering) Orellana & Sansón, 2019. AphiaID: 1465502.

Classification: Biota; Chromista; Harosa; Heterokonta; Ochrophyta; Phaeophyceae; Fucophycidae; Fucales; Sargassaceae; Cystoseira