Polysiphonia
| Polysiphonia | |
|---|---|
| Scientific classification | |
| Domain: | Eukaryota |
| (unranked): | Archaeplastida |
| Division: | Rhodophyta |
| Class: | Florideophyceae |
| Order: | Ceramiales |
| Family: | Rhodomelaceae |
| Genus: |
Polysiphonia Greville, 1823 |
Polysiphonia is a genus of filamentous red alga with about 19 species on the coasts of the British Isles and about 200 species world-wide, including Crete in Greece, Antarctica and Greenland. Its members are known by a number of common names. It is in the Order Ceramiales and Family Rhodomelaceae.
Polysiphonia is a red alga, filamentous and usually well branched, with some plants reaching a length of about 30 cm. They are attached by rhizoids or haptera to a rocky surface or other alga. The thallus (tissue) consists of fine branched filaments each with a central axial filament supporting pericentral cells. The number of these pericentral cells, 4–24, is used in identification. Polysiphonia elongata shows a central axial cell with 4 periaxial cells with cortical cells growing over the outside on the older fronds. Its cuticle contains bromine.
Features used in identification include the number of pericentral cells, the cortication of main branches, constriction of young branches at their base, whether the branching dichotomous or spiral, and the width and length of thalli.
Species have been recorded from Europe, Australia and New Zealand, North America and South America, islands in the Pacific Ocean, South Africa, southwest Asia, Japan, Greenland and Antarctica.
The species are entirely marine, found growing on rock, other algae, mussels or limpets and artificial substrata etc. from mid-littoral to at least 27 m depth. Many species are abundant in rock pools. Polysiphonia lanosa is commonly found growing on Ascophyllum nodosum.
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