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Rhodophyta, Red Algae

Gymnogongrus griffithsiae

Rhodophyta, Order: Gigartinales; Family: Phyllophoraceae.


Gymno means ‘uncovered’, referring to its smooth shape, and a lack of hair on the thallus. And gongrus describes the rounded shape of thallus. The species name is dedicated to the British researcher,A.W. Griffiths.


The Gymnogongrus griffithsiae is a small alga with bald and cartilaginous branches, characterized by their frequent dichotomous branching. Along the thallus, at a frequency of 1 or 2 cm, five or six splits occur more on less on the same plane. The frequent branching results in many branches emanating from a single branch, and the widening gives the thallus a rounded appearance. The branch edges are

rounded. A microscopic cross-section of the thallus reveals a difference in cellular arrangement at the centre of the thallus, compared to its side: the inner cells are large, light and rounded, whereas along the perimeter, several (four to six) rows of small cells are densely arranged.


The Thallus we found reached 2 cm, but according to literature, the alga grows up to 5 cm. The branch width is about 0.5 mm.


The alga is usually coloured in dark shades between bright red and brownish-black.

Special features

An outstanding feature of the Gymnogongrus griffithsiae



Gymnogongrus griffithsiae (Turner) Martius

 is its dense dichotomous branching that results in a widening of branches.


The alga has mostly been found in shaded habitats: potholes and underwater caves. It may also be found in other places but, due to the scarcity of information, this is hard to determine. In other locations around the world, it has been reported as an epiphyte that can withstand immersion by sand, so long as the substrate is rocky.

Biology and reproduction

Reproductive organs are conspicuous year round, and are located at the base of the thallus’ branches. They are darkly coloured and contain the reproductive cells. The Gymnogongrus griffithsiae’s life cycle is unusual; the

Gymnogongrus griffithsiae -general view of the thallus.

Gymnogongrus griffithsiae - a cross section of the thallus. On the perimeter, several rows of small cells are evident, characteristic of the outer layer (cortex).

gametophytes and sporophytes separate, and each undergoes sexual reproduction separately. Tetrasporangial plants are unknown.

Seasonality and distribution:

The Gymnogongrus griffithsiae is prevalent throughout the year. Often, the algae disappear, but this may be due to the activity of fish or other factors, and they later reappear in the same location. The worldwide distribution of the species is primarily in the Mediterranean, and some claim the species to be endemic there, although reports have arrived from the Canary Islands and Brazil.

Additional species

As far as is known, this species is the sole member of the Gymnogongrus reported in the Eastern Mediterranean.

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