Phaeophyta, Brown Algae

Cystoseira dubia Valiante

Phaeophyta,  Order: Fucales; Family: Cystoseiraceae.


Cystoseira means ‘chain of vesicles’ and it describes the air pockets in the thallus. The scientific name of the species, dubia, is given in honour of the botanist J. E. Duby.


A small, delicate, rounded species. The toful (the condensation at the base of the central branches) is partial, delicate, smooth and connected to the stipe. The central axis crawls (resembling a runner) and develops inside the substrate. The central branch and secondary branches are flattened.


Most individuals found were smaller than 15 cm in length.


The species comes in shades light of brown and cream, sometimes uniformly and sometimes with spots. When dried, the thallus acquires a darker shade.

Special features

Characteristic signs of the species include the flattened shape and the deep-sea habitat.


Cystoseira dubia penetrates the sea deeper than any other species of Cystoseira. It is usually in deep water, and individuals have been found at depths of between 20-150 m.