Blue Ecosystems יעוץ סביבתי, בהנהלת ד"ר רחלי עינב - Polysiphonia_Greville

 

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דף הבית >> Seaweeds of Eastern Mediterranean coast >> Rhodophyta >> Polysiphonia_Greville
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Rhodophyta | Chlorophyta | Rhodophyta
Polysiphonia  Greville, 1823






Taxonomy
Rhodophyta, Order: Ceramiales; Family: Rhodomelaceae.
Etymology
The Scientific name describes the algal shape, meaning (literally) many tubes.
Description
The Polysiphonia resembles a cluster of thin, soft, red filaments. To discern the details of its structure and identify the species, a microscope is required. The edges of the branches are sharp and sometimes covered with single- rowed, tangled hair. At the centre of each branch, a single, central, transparent, colourless cell is surrounded by thin cells containing pigment. The coloured cells are arranged along the joint-like branch.
Size
The branches are less than 1 mm in width. Their length is between several mm to 15 cm.
Colour
The Polysiphonia is a very dark crimson red. When dried, it tends towards black.
Special features
The Polysiphonia resembles a cluster of thin red filaments. To identify the species, a microscope is required. Taxonomy is primarily based upon the shape of the sporangium.
Habitat
The Polysiphonia usually appears on rocks near the beach as an epiphyte on sea creatures and other algae. When growing upon other plants, it has the ability to penetrate the host’s cells. Concentrations of algae can be found in distant potholes that receive a regular water supply but are inaccessible to fish.
Biology and reproduction
The life cycle incorporates three generations; the gametophyte and sporophyte resemble each other in shape (isomorphic), and the additional generation is heteromorphic. This last is an asexual generation (sporophyte) that lives as a parasite on the female gametophyte. The parasitic generation is called a cystocarp, and it is oval and elliptic in shape. The cystocarp is transparent and resembles a vase or an egg. Through it, one may see groups of spores arranged in couples. The spores germinate an independent sporophytic generation (asexual, diploid) that resembles a gametophyte in shape. The spores are to be found one on each joint, forming a sort of thickening that pinpoints their location. The Polysiphonia is one of the first species in which the three-stage life cycle was researched and, therefore, the species is mentioned in many phycology (the study of algae) books.
The Polysiphonia is also favoured by fish. Stomach examinations of fish reveal remnants of the alga at a rate higher than natural supply. It would seem that the biological activity of fish is aimed at distributing the algae throughout the sea.
Seasonality and distribution
Polysiphonia species can be found along the coast throughout the year, especially during summer.
Additional species
The Polysiphonia genus is a large one and includes more than 150 species that are very difficult to identify. About thirty species have so far been identified in this region, out of which I will list three that are often mentioned in various publications.
Polysiphonia elongata (Hudson) Sprengel
Polysiphonia opaca (C. Agardh) Moris and De Notaris
Polysiphonia violacea (Roth) Sprengel .
Recent laboratory tests show that at least some of the Polysiphonia species have antibiotic properties that act against fungi and bacteria. In Turkey, the plant was used as a remedy that increases fat-dissolving activities in the blood system.
 

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