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Rhodophyta, Red Algae

Solieria filiformis (Kutzing ) Gabrielson

Rhodophyta, Order: Gigartinales; Family: Solieriaceae.


The scientific name of the genus, Solieria, is dedicated to the French scientist, A. J. J. Solier. The species name describes the algal filamentous shape.


The Solieria filiformis is a smooth, mucousy and cartilaginous alga with cylindrical branches that are very flexible and branch dichotomously. A cross section reveals an elongated medulla in the centre, perpendicular to the cut )that is executed across the width of the alga).


The diameter of the thallus measures between 1-2 mm, and the alga may reach 10 to 20 cm in length. It is often eaten at sea, and then, of course, has shorter branches.


The Solieria filiformis is usually a murky beige-brown. Red individuals are sometimes found.

Special features

For absolute identification, a lateral cut must be made to the thallus. At its centre are linear cells. Previously, the Solieria filiformis was erroneously classified as a species of the Gelidiopsis. But a microscopic cross section shows that this species is quite different, characterized by its medulla ( a layer of inner cells) that contains relatively small cells with a very thick wall.



Solieria filiformis a lateral section of the thallus showing the elongated cells of the inner layer (medulla).


The Solieria usually grows in the upper regions of the intertidal zone, in potholes and shallow pools on the platform. The alga is very sensitive to dehydration, and exposed individuals decompose and turn white.

Biology and reproduction

Fertile individuals have not yet been found in Israel, and in aquaculture pools the alga succeeds in growing without completing its life cycle. Based on reports from other countries (including England and Italy) fertile individuals are not easily found, and the life cycle might not be complete at sea, either.

Seasonality and distribution

The alga can be found during most seasons, and it is often the dominant species in its habitat. During winter, a rise in the population has been noticed. Along the Eastern Mediterranean’s rougher coasts, individuals are found clinging to a substrate, but in other places they have reportedly been found floating. This characteristic, among others, enables agricultural cultivation. The alga is very common along Mediterranean coasts. Some claim that a rise in population has lately been observed along Israeli coasts; however, it is impossible to determine whether this is accurate or a result of past difficulty in identification.


The Solieria filiformis is an important source of carrageenan. In Israel, it is cultivated in the aquaculture pools of Kibbutz Rosh Hanikra for economic purposes. The alga is tasty, even to those who are not familiar with eating algae.

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