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Rhodophyta, Red Algae

Pterocladiella capillacea (Gmelin) Santelices & Hommersand

Rhodophyta, Order: Gelidiales; Family: Gelidiaceae.


Pterocladiella means a ‘feathery branch’, referring to the feather-like shape of the thallus. Recently, the generic name was changed from Pterocladia (which it was called for many years) to Pterocladiella. Capillacea, means ‘hairy-like’.


The Pterocladiella capillacea is a large alga found in great amounts and dense clusters. The flattened ‘leaves’ resemble

feathers. The thallus is slightly cartilaginous. All the branches grow on a plane and have a central axis from which side branches fan out in several groupings. The rhizoid emanates from the inside of the thallus.


The branches grow 5 to 15 cm in height. They grow to a width of 1 or 2 mm, and a single thallus grows to a width of 5 cm and rarely 8 cm.


Most individuals are darkly coloured in bright burgundy.

The feather-like thallus of the Pterocladiella


Special features

It is usually quite easy to identify the Pterocladiella capillacea by its branched, feathery thallus and its red colour. Identification may be aided by habitat and distribution. It is sometimes difficult to distinguish the Pterocladiella from the Gelidium. See detailed description under Gelidium.


The Pterocladiella capillacea’s typical habitat is the tight belt around the upper region of the subtidal zone. It is rarely exposed to air at low tide, but neither does it grow in the depths. Its natural habitat is characterized by strong water turbulence, due to waves breaking upon the abrasion platform. The Pterocladiella’s habitat requires a strong holdfast to prevent the thallus from becoming detached in rough seas.

Biology and reproduction

The Pterocladiella has a three-staged life cycle. Reproductive spores are located at the edges of branches and can be seen through a magnifying glass as dark spots. Four spores are arranged in the form of a cross. The cystocarps (sporangium) resemble protruding swellings at the edges of the branches.

The Pterocladiella is an important agar-producing plant and is also used in research. Cultivated colonies indicate that it can produce different qualities of agar, in accordance with the cultivation conditions in a laboratory and the individuals’ respective genetic qualities.

Seasonality and distribution

The Pterocladiella capillacea is a common species and can be found on nearly any rocky shore throughout the year. Its global distribution spreads from Norway, in the north, through the Atlantic Ocean, the Canary Islands and to the Mediterranean.

Additional species

Apparently, the only species is the genus in our region.


Local inhabitants in New Zealand and other places have used the Pterocladiella plant to stimulate the fat dissolving process in the blood system. The alga is also used to manufacture agar.

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