Polysiphonia Greville, 1823: pl. 90

Classification:
Empire Eukaryota
Kingdom Plantae
Phylum Rhodophyta
Subphylum Eurhodophytina
Class Florideophyceae
Subclass Rhodymeniophycidae
Order Ceramiales
Family Rhodomelaceae
Tribe Polysiphonieae

Holotype species: Polysiphonia urceolata (Lightfoot ex Dillwyn) Greville

Currently accepted name for the type species: Polysiphonia stricta (Dillwyn) Greville

Original publication and holotype designation: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.
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Taxonomic status: currently recognized as a distinct genus.

Description: Thallus developing a primary erect system of cylindrical polysiphonous branches, mostly having indeterminate growth; prostrate branches often developed secondarily by attaching decumbent branches or determinate attaching branches; rhizoids, mostly unicellular, formed by pericentral cells, from which they are usually separated by a cell wall and pit connection, on ventral sides of decumbent and attaching branches in most species, sometimes epiphytic species forming a discoid cellular attachment derived from germling; secondary rhizoids derived from axial cells in P. lanosa (Rawlence & Taylor, 1972); upright branches having 4-25 (or more) pericentral cells, the number often characteristic for species, pericentral cells the same length as the axial cells; rhizoidal or pseudoparenchymatous cortication sometimes formed from pericentral cells, especially in proximal parts of main branches; distal tips of branches usually straight, with a conspicuous apical cell and forming exogenous branches, in a spiral, of two types, monosiphonous trichoblasts and polysiphonous branches; trichoblasts without chloroplasts and usually branched once to many times, usually deciduous soon after formation; some trichoblasts non-emergent and unicellular forming scar cells; other scar cells the result of the breaking off of trichoblasts leaving behind the embedded basal cell; polysiphonous branches may develop from scar cells on older parts of branches (cicatrigenous development) or endogenous-adventitiously from unpredictable parts of the thallus. Gametangial plants usually dioecious, isomorphic; spermatangia borne in cylindrical to pyramidal capitula, replacing trichoblasts or one of the lower branches of a trichoblast, with or without a terminal sterile cell(s) on the capitulum axis; carpogonial branches borne in positions of trichoblasts but on short polysiphonous branchlets, pericarpial cells surround early stages of procarp development and a trichoblast is also usually attached, post-fertilization results in great enlargement of the pericarp to form a variously shaped, often globose, cystocarp in which large lacrimiform carposporangia are produced on short gonimoblast filaments emerging from a fusion cell; tetrasporangia produced on diploid plants that are isomorphic with gametophytes, tetrahedrally divided, borne singly in a series of segments usually toward distal parts of branches, in a spiral or straight row in the branch. A few species form asexual propagules (Kapraun 1977, Womersley 1979), propagation by fragmentation is possible.

Comments: Polysiphonia resembles several other genera, its species may especially be confused with those of Lophosiphonia, Womersleyella and Pterosiphonia. Unlimited growth of a system of dorsiventral prostrate branches separates Lophosiphonia and Womersleyella from Polysiphonia and the former two genera have a more limited upright branching system, secondarily derived, endogenously in Lophosiphonia and cicatrigenously from non-emergent trichoblasts in prostrate branches of Womersleyella. Branches of Pterosiphonia are bilaterally symmetrical and flattened, with congenital fusion of branches and axis, whereas those of Polysiphonia always are cylindrical and without such fusions. Species of Polysiphonia occur in most marine regions of the world, often as epiphytes on larger plants in the sea but also epizooic on various invertebrates and on sea turtles. Many other species occur on rocks. Polysiphonia sometimes may be found in mangrove habitats as well as in estuaries, sometimes in almost freshwater habitats.

NCBI Nucleotide Sequences

Numbers of names and species: There are 993 species (and infraspecific) names in the database at present, of which 196 have been flagged as currently accepted taxonomically.

Names: ('C' indicates a name that is currently accepted taxonomically; 'S' a homotypic or heterotypic synonym; 'U' indicates a name of uncertain taxonomic status, but which has been subjected to some verification nomenclaturally; 'P' indicates a preliminary AlgaeBase entry that has not been subjected to any kind of verification. For more information on a species click on it to activate a link to the Species database):

References
Wynne, M.J. & Schneider, C.W. (2010). Addendum to the synoptic review of red algal genera. Botanica Marina 53: 291-299.

Contributors
Some of the descriptions included in AlgaeBase were originally from the unpublished Encyclopedia of Algal Genera, organised in the 1990s by Dr Bruce Parker on behalf of the Phycological Society of America (PSA) and intended to be published in CD format. These AlgaeBase descriptions are now being continually updated, and each current contributor is identified above. The PSA and AlgaeBase warmly acknowledge the generosity of all past and present contributors and particularly the work of Dr Parker.

Descriptions of chrysophyte genera were subsequently published in J. Kristiansen & H.R. Preisig (eds.). 2001. Encyclopedia of Chrysophyte Genera. Bibliotheca Phycologica 110: 1-260.

Linking to this page: http://www.algaebase.org/search/genus/detail/?genus_id=37461

Citing AlgaeBase
Cite this record as:
Guiry, M.D. & Guiry, G.M. 2013. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org; searched on 24 May 2013.

Algaebase taxon LSID: urn:lsid:algaebase.org:taxname:8028