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Phaeophyta, Brown Algae

Hydroclathrus clathratus (Bory and C. Agardh) Howe

Phaeophyta,  Order: Scytosiphonales; Family: Scytosiphonaceae.


The generic name, Hydroclathrus, includes the words ‘water’ and ‘mesh’. Clathratus, also means ‘mesh’ or ‘fishing net’.


The Hydroclathrus clathratus resembles an oval ball of mesh. Holes in the mesh tend towards round, but they are irregular and unequal in size. The thallus is rigid, slightly mucousy and smooth. Microscopic examination reveals the thallus to be constructed of three layers, the outer ones containing small cells with flattened chloroplasts. Cavities containing hair are spread along the thallus’ surface.


The alga is usually smaller than 10 cm in diameter. Rarely, a concentration of individuals may be seen.


The Hydroclathrus clathratus is light brown. Beached individuals sometimes pale and turn white.

Special features

The mesh structure that resembles a delicate sponge is its characteristic.


The Hydroclathrus clathratus usually grows in the subtidal zone, but is sometimes exposed to the air. Evidence has been heard of the algal presence in the deep sea, but no such report has emanated as yet from our region.



Biology and reproduction

The Hydroclathrus clathratus’s reproductive cells are biflagellate. Reproductive cells have been known to concentrate in large aggregates, but their life cycle has not yet been studied in detail.

Seasonality and distribution

The Hydroclathrus clathratus has lately become quite rare along Eastern Mediterranean shores. An individual may sometimes be found washed ashore, but this species, too, seems to be in danger of extinction from our shores. In the past, it was common throughout the year. The Hydroclathrus clathratus is common in tropical seas worldwide.

Additional species

The Hydroclathrus clathratus is the only species in this genus.

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