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Phaeophyta, Brown Algae

Petalonia fascia (M.ller) Kuntze

Phaeophyta,  Order: Scytosiphonales; Family: Scytosiphonaceae.


The generic name, Petalonia, means ‘leaf-like’. Fascia means ‘clustered’, due to the arrangement of the strands of the thallus that emanate from a common holdfast.


The Petalonia resembles a cluster of brown strands. The strands are narrow at the base and edges, and emanate from a common base. The holdfast is formed in the shape of a round disk whose diameter is smaller than the width of the alga.


Local individuals reach a length of about 15 cm. Their width is not usually more than 1 cm. Like many species, the Eastern Mediterranean variety is smaller and, in other places, individuals reach a length of 40 - 50 cm.


The brown colour of the strands ranges from dark brown to greenish-brown.

Special features

Brown strands that resemble the texture of the Ulva but are smaller. The thallus shape and colour change in accordance with environmental conditions, temperature and radiation level.


The Petalonia can usually be found in the upper regions of the intertidal zone and above the intertidal zone, attached to rocks that are immersed in the water or platforms on abrasion platforms. The Petalonia grows on gravel and limestone, sometimes as an epiphyte upon other algae.

Biology and reproduction

All Petalonia individuals are believed to be diploid, and the haploid phase is believed to have disappeared (universal life cycle). The spores are arranged in vertical rows before the thallus. In America and Japan, several research projects have focused on the algal life cycle, and variations have been found between various colonies of the species.

Seasonality and distribution

The Petalonia seems to appear along the coast in waves. It is not a common species but may in the future, upon additional sightings, turn out to be less rare than previously thought. The species has a wide distribution, especially in northern regions, and several sub-species are recognized. This species has been reported in the Pacific Ocean and the Atlantic Ocean.

Additional species

As far as is known, the Petalonia fascia is the only species in this region.

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