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Name derivation:

Polysiphonia  Greville= Gr. polus, poly: many + siphon: tube or pipe; “with many tubes”
subtilissima= L. subtilissima: most slender or very delicate


Polysiphonia  Greville  1823;  196 of 992 species descriptions are currently accepted taxonomically (Guiry and Guiry 2014).

Order Ceramiales;  Family Rhodomelaceae



Filaments are polysiphonous with 4-14 pericentral cells and often abundantly branched; prostrate axes produce erect axes and are attached by rhizoidal holdfasts from basal cells of erect axes or ventral cells of prostrate axes.  Rhizoids of some species have an open cytoplasmic connection with pericentral cells while others have a cross wall.  Erect axes are terete and cortication, if present, is usually derived by divisions of pericentral cells.  Secondary pit connections are either present or absent.  Growth is by an apical cell; branches produce secondary ones or hyaline determinate trichoblasts that are branched or unbranched, often deciduous, and produce scar cells.  Tetrasporangia are tetrahedrally divided.  Gametophytes are dioecious.  Spermatangial sori are conical or cylindrical and on short, uniseriate stalks of trichoblasts.  Procarps are near branch tips on the second cell of reduced trichoblasts; carpogonial branches are 4-celled; cystocarps are ostiolate and ovoid or vase-shaped.

At least 11 species of Polysiphonia are presently recorded from the Northwest Atlantic, including P. arctica, P. brodiaei, P. elongata, P. fibrillosa, P. flexicaulis, P. fucoides, P. lanosa (= Vertebrata lanosa of some authors), P. nigra, P. schneideri  (formerly P. denudata), P. stricta, and P. subtilissima. Although vegetative features are useful, species identifications can be difficult  (Kapraun, 1977, 1978; Kapraun and Rueness 1981; Schneider and Searles, 1991; Taylor 1957).

General references on the genus Polysiphonia include Abbot and Hollenberg (1976), and descriptions of local records in New England, USA are in Hehre and Mathieson (1970).

Similar species:

Chondria, Neosiphonia, and Rhodomela

Bioaccumulation of heavy metals:

In a study examining the 26 dominant macroalgae of the Gulf of Thessaloniki in the Aegean sea, Polysiphonia species were found to be the greatest bioaccumulators of cadmium, and also indicated morphological attributes that may lead to greater bioaccumulation capabilities. As a filamentous seaweed, Polysiphonia was found to be a better bioaccumulator of a wide set of elements  including cadmium, copper, magnesium, nickel, lead, and zinc  as compared to sheet-like, coarsely-branched, and thick-leathery macrogalgal morphologies also found within the site. As a result, the morphology of Polysiphonia suggests that the accumulation of several elements is largely related to thallus structure and growth strategy. (Malea and Keverkidis, 2014)


Attached to rocks or epiphytic on larger seaweeds and eelgrass (e.g. Zostera marina). Various species fluorishes in different habitats and at different times of the year.

In the Northwest Atlantic it can be locally common, often found in estuaries, salt marshes and mudflats in brackish to almost fresh water habitats. Known as disjunct populations from the Gulf of St. Lawrence to Long Island, then continuous in salt marshes south to Florida, the Caribbean, Bermuda, the Gulf of Mexico, French Guiana; also found in the Mediterranean, the Ascension, Cape Verde, and St. Helena Islands, Africa, Chile, Korea, the Indo-Pacific, New Zealand, and Australia.


Invasive Species:

One particular species of the Japanese marcoalga Polysiphonia, P. morrowii, has recently been identified as the first record of this invasive macroalga on the South Altantic Ocean, in addition to being the first record of an invasive species related to the establishment of the Pacific oyster, C. gigas, in Atlantic Patagonia. Misidentified in 1994 as another member of the Polysiphonia genus, the current invasive Polysiphonia species is found almost all year round at the site, with higher abundance in the autumn and winter. (Croce and Parodi, 2014).




Abbott I. A. and G. J. Hollenberg. 1976, Marine Algae of California. Stanford University Press, Stanford, xii + 827 pp.

Croce, E. M. and E. R. Parodi  2014. The Japanese alga Polysiphonia morrowii (Rhodomelaceae Rhodophyta) on the South Atlantic Oyster: first report of an invasive macroalga inhabiting oyster reefs. Helgoland Marine Research 68(2): 241 – 252.

Greville, R.K.  1823.  Scottish cryptogamic flora, or coloured figures and descriptions of cryptogamic plants, belonging chiefly to the order Fungi; and intended to serve as a continuation of English Botany. Vol. 2 (fasc. 7-12), Plates 31-60. Edinburgh & London: MacLachlan & Stewart; Baldwin, Craddock & Joy. Guiry, M.D. and G.M. Guiry  2013.  AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org; searched on 07 May 2013.

Hehre, E. J. and A. C. Mathieson. 1970. Investigations of New England marine algae. III. Composition, seasonal occurrence and reproductive periodicity of the marine Rhodophyceae in New Hampshire. Rhodora 72: 194-239.

Kapraun, D. F. 1977. The genus Polysiphonia in North Carolina, USA. Bot. Mar. 20: 313-331.

Kapraun, D. F. 1978. Field and cultural studies on selected North Carolina Polysiphonia species. Bot. Mar. 21: 143-153.

Kapraun, D. F. and J. Rueness. 1983. The genus Polysiphonia (Ceramiales, Rhodomelaceae) in Scandinavia. G. Bot. Ital. 117: 1-30.

Maggs, C.A. and M. H. Hommersand  1993. Seaweeds of the British Isles. Volume 1: Rhodophyta. Part 3A: Ceramiales. London, HMSO, for Natural History Museum.

Malea, P. and T. Kevrekidis  2014. Trace element patterns in marine macroalgae. Science of the Total Environment. 494 – 495: 144 – 157.

Schneider, C. and R. B. Searles. 1991. Seaweeds of the Southeastern United States, Cape Hatteras to Cape Canaveral. Duke Univ. Press, Durham, xiv + 553 pp.

Taylor, W. R. 1957. Marine Algae of the Northeastern Coast of North America. Revised edition. Univ. Michigan Press., Ann Arbor, ix + 509 pp.