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Rhodophyta, Red Algae

Rhodymenia ardissonei J. Feldmann

Rhodymenia, Order: Rhodymeniales; Family: Rhodymeniaceae.


Rhodon means ‘red’, referring to the algal colour. Ardissonei is named after the Italian phycologist, F. Ardissone.


The Rhodymenia ardissonei is a flattened alga, often translucent, and dichotomously branched.


The alga grows from 1 to 2 cm in length, and its width is less than 1 mm. In other places around the world, larger individuals have been found.


The alga is red, ranging from bright red to reddish brown or orange. Young individuals have a relatively dense protoplasm, which gives them a darker shade.

Special features

The Rhodymenia ardissonei is a small dichotomous alga, which develops in the subtidal zone in shaded and crowded areas.


The Rhodymenia ardissonei grows in the subtidal zone in potholes, caves and deep water, usually in shaded areas amongst dense colonies of other algae and sponges where there is a high level of competition.

Biology and reproduction

The reproductive cells are generated on both sides of the thallus, often in great density. Two cycles of development and the release of reproductive cells from the same thallus have been observed. The sexual and asexual stages of the algae are quite similar. The sexual stage is easily identified, occurring when the thallus holds reproductive cells that resemble black spots.

Seasonality and distribution

The Rhodymenia ardissonei grows along the coast throughout the year; however, it is not very common but enjoys a wide global distribution.

Additional species

A number of species have been reported in this region. In Egypt, individuals belonging to the following species, which drifted in from the depths, have been collected:

Rhodymenia erythraea Zanardini and Rhodymenia ligulata Zanardini. In Israel, Rhodymenia pseudopalmata (Lamouroux) Silva, has been found.


Larger species belonging to this genus have a very high protein level and are consumed in several countries.

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