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Chlorophyta, Green Algae

Ulva laetevirens Areschoug = Ulva rigida C. Agardha

Chlorophyta, Order: Ulvales; Family: Ulvaceae.


The scientific name of the alga, Ulva, is the ancient name originally given to all algae. Since the days of Linnaeus, the name has been dedicated to the algae most dominant in nature. Ulva laetevirens has a harder thallus than other species of Ulva, and hence its name, rigida. The scientific name, laetevirens means ‘greenish’, ‘light green’.


The Ulva laetevirens connects to the substrate using a round disk. Usually more than one thallus emanates from the same holdfast. The thallus’ edge has microscopic perforations, some that resemble teeth (several cells each) and some simpler. The cells are scattered and not arranged in rows. The thallus is comparatively thick, and it measures near the holdfast 150 microns in width. Usually 2 Pyrenoids.


The thallus varies in size in accordance with environmental conditions. Usually, individuals have thalli ranging between 10-15 cm; however, lengths of 30 cm are not uncommon. The bottom of the thallus measures 117-187 microns in width.


The Ulva laetevirens’ thallus is intense green. Ulva laetevirens -an overview of the central part of the thallus, Cells are usually dispersed and are sometimes arranged.

Special features

The characteristics of the Ulva laetevirens include its hard thallus and the proliferation at the edges of the thallus (these can be seen in the field using a magnifying glass).

Habitat The Ulva laetevirens grows in potholes on the abrasion platform and sometimes also in the subtidal zone. Epiphytic individuals have been spotted on snails, Cystoseira bushes or other algae that develop under water.

Biology and reproduction

See entry under Ulva.

Seasonality and distribution

This species is apparently very common along the coast; Ulva lactuca individuals erroneously described in the region may actually have been Ulva laetevirens. The species is widely distributed and has been spotted in the Mediterranean and along American and South African shores.



In Japan, the Ulva laetevirens is used for human consumption, medicine and cosmetics. As a therapeutic plant, its indications are arthritis and mumps )inflammation of the lymphatic nodes). In cosmetics, it is used to prepare facemasks and to induce skin pore reduction.

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