Gigartina pistillata is a red algae, belonging to the phylum Rhodophyta and the order Gigartinales. The main component of the cell wall and intracellular matter of these living beings is a mucilaginous substance, carrageenan, one of the most important polysaccharides in the phylum Rhodophyta. This alga is characterized by a robust, branched, dark red stalk, which can reach between 5 and 15 cm in height, adhering to rocky substrates through its basal disc in areas of strong hydrodynamism. It is commonly found along the Northeast Atlantic and Mediterranean coasts.