''Polysiphonia'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomencla ...

of filamentous

red algae Red algae, or Rhodophyta (, ; ), are one of the oldest groups of eukaryotic algae. The Rhodophyta also comprises one of the largest phyla of algae, containing over 7,000 currently recognized species with taxonomic revisions ongoing. The majority ...

with about 19

species In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of ...

on the coasts of the

British Isles The British Isles are a group of islands in the North Atlantic Ocean off the north-western coast of continental Europe, consisting of the islands of Great Britain, Ireland, the Isle of Man, the Inner and Outer Hebrides, the Northern Isles, ...

and about 200 species worldwide, including

Crete Crete ( el, Κρήτη, translit=, Modern: , Ancient: ) is the largest and most populous of the Greek islands, the 88th largest island in the world and the fifth largest island in the Mediterranean Sea, after Sicily, Sardinia, Cypru ...

Greece Greece,, or , romanized: ', officially the Hellenic Republic, is a country in Southeast Europe. It is situated on the southern tip of the Balkans, and is located at the crossroads of Europe, Asia, and Africa. Greece shares land borders with ...

Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest contine ...

and

Greenland Greenland ( kl, Kalaallit Nunaat, ; da, Grønland, ) is an island country in North America that is part of the Kingdom of Denmark. It is located between the Arctic and Atlantic oceans, east of the Canadian Arctic Archipelago. Greenland is ...

. Its members are known by a number of common names.Recorded common names are olann dhearg, craonach, cúnach triosgar, cluaisíní, mileara, millreacha, salata tou yialou (σαλάτα του γιαλού) and lobster horns. It is in the order Ceramiales and family Rhodomelaceae.

Description

''Polysiphonia'' is a red algae, polysiphonous and usually well branched, with some plants reaching a length of about 30 cm. They are attached by

rhizoid Rhizoids are protuberances that extend from the lower epidermal cells of bryophytes and algae. They are similar in structure and function to the root hairs of vascular land plants. Similar structures are formed by some fungi. Rhizoids may be uni ...

s or

haptera A holdfast is a root-like structure that anchors aquatic sessile organisms, such as seaweed, other sessile algae, stalked crinoids, benthic cnidarians, and sponges, to the substrate. Holdfasts vary in shape and form depending on both the spec ...

to a rocky surface or other alga. The

thallus Thallus (plural: thalli), from Latinized Greek (), meaning "a green shoot" or "twig", is the vegetative tissue of some organisms in diverse groups such as algae, fungi, some liverworts, lichens, and the Myxogastria. Many of these organisms wer ...

(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

frond A frond is a large, divided leaf. In both common usage and botanical nomenclature, the leaves of ferns are referred to as fronds and some botanists restrict the term to this group. Other botanists allow the term frond to also apply to the lar ...

s. 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 A dichotomy is a partition of a whole (or a set) into two parts (subsets). In other words, this couple of parts must be * jointly exhaustive: everything must belong to one part or the other, and * mutually exclusive: nothing can belong simult ...

spiral In mathematics, a spiral is a curve which emanates from a point, moving farther away as it revolves around the point. Helices Two major definitions of "spiral" in the American Heritage Dictionary are:Europe, Australia and

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island country ...

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the C ...

and South America, islands in the

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the contin ...

South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. It is bounded to the south by of coastline that stretch along the Atlantic Ocean, South Atlantic and Indian Oceans; to the ...

, southwest

Asia Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an area ...

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

, Greenland and Antarctica. The species are entirely marine, found growing on rock, other algae,

mussel Mussel () is the common name used for members of several families of bivalve molluscs, from saltwater and freshwater habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other edible clams, which ...

s or

limpet Limpets are a group of aquatic snails that exhibit a conical gastropod shell, shell shape (patelliform) and a strong, muscular foot. Limpets are members of the class Gastropoda, but are polyphyletic, meaning the various groups called "limpets" ...

s and artificial substrata etc. from mid-

littoral The littoral zone or nearshore is the part of a sea, lake, or river that is close to the shore. In coastal ecology, the littoral zone includes the intertidal zone extending from the high water mark (which is rarely inundated), to coastal areas ...

to at least 27 m depth. Many species are abundant in rock pools. '' Polysiphonia lanosa'' is commonly found growing on '' Ascophyllum nodosum.''

Reproduction and life cycle

The life-cycle of the red algae has three stages ( triphasic). In ''Polysiphonia'' it consists of a sequence of a gametangial, carpospoangial and tetrasporangial phases.Smith, G.M. 1955. ''Cryptogamic Botany Algae and Fungi. Volume 1.'' Second Edition. p.337 Male (

haploid Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Sets of chromosomes refer to the number of maternal and paternal chromosome copies, respecti ...

) plants (the male

gametophyte A gametophyte () is one of the two alternating multicellular phases in the life cycles of plants and algae. It is a haploid multicellular organism that develops from a haploid spore that has one set of chromosomes. The gametophyte is the se ...

s) produce

sperm Sperm is the male reproductive cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive cell and a smaller, male one). Animals produce motile sperm with a tail known as a flagellum, wh ...

atia and the female plants (the female gametophytes) produce the carpogonium (the haploid

carpogonium The carpogonium (plural ''carpogonia'') is the female organ in the Red Algae (Rhodophyta) which have a highly specialized type of reproduction. It contains the reproductive nucleus. It may contain a number of cells usually without chloroplasts. It s ...

) which remains attached to the parent female plant. After fertilization the

diploid Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Sets of chromosomes refer to the number of maternal and paternal chromosome copies, respectiv ...

nucleus Nucleus ( : nuclei) is a Latin word for the seed inside a fruit. It most often refers to: *Atomic nucleus, the very dense central region of an atom *Cell nucleus, a central organelle of a eukaryotic cell, containing most of the cell's DNA Nucle ...

migrates and fuses with an auxiliary cell. A complex series of fusions and developments follow as the diploid

zygote A zygote (, ) is a eukaryotic cell formed by a fertilization event between two gametes. The zygote's genome is a combination of the DNA in each gamete, and contains all of the genetic information of a new individual organism. In multicellula ...

develops to become the carposporophyte, this is a separate phase of the life-cycle and is entirely

parasitic Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...

on the female, it is surrounded by the haploid pericarp of the parent female plant. The diploid

carpospore A carpospore is a diploid spore produced by red algae. After fertilization, the alga's carpogonium subdivides into carpospores, and generally the largest type of spore (larger than bispores, which are larger again than tetraspores Tetraspores are ...

s produced in the carposporangium when released are non-motile, they settle and grow to form filamentous diploid plants similar to the gametophyte. This diploid plant is the tetrasporophyte which when adult produced spores in fours after meiosis. These spores settle and grow to become the male and female plants thus completing the cycle.

Species

The species currently recognized are: *'' P. abscissa'' *'' P. abscissoides'' *'' P. acanthina'' *'' P. acuminata'' *'' P. adamsiae'' *'' P. adriatica'' *'' P. amphibolis'' *'' P. anisogona'' *'' P. anomala'' *'' P. arachnoidea'' *'' P. arctica'' *'' P. aterrima'' *'' P. atlantica'' *'' P. atra'' *'' P. atricapilla'' *'' P. australiensis'' *'' P. azorica'' *'' P. bajacali'' *'' P. banyulensis'' *'' P. barbatula'' *'' P. baxteri'' *'' P. beaudettei'' *'' P. beguinotii'' *'' P. bicornis'' *'' P. biformis'' *'' P. bifurcata'' *'' P. binneyi'' *'' P. blandii'' *'' P. boergesenii'' *'' P. boldii'' *'' P. breviarticulata'' *'' P. brevisegmenta'' *'' P. brodiei'' *'' P. caespitosa'' *'' P. callithamnioides'' *'' P. cancellata'' *'' P. capucina'' *'' P. carettia'' *'' P. caspica'' *'' P. castagnei'' *'' P. castelliana'' *'' P. ceramiaeformis'' *'' P. cladorhiza'' *'' P. coacta'' *'' P. codicola'' *'' P. collinsii'' *'' P. confusa'' *'' P. constricta'' *'' P. corymbosa'' *'' P. crassa'' *'' P. crassicollis'' *'' P. crassiuscula'' *'' P. curta'' *'' P. dasyoeformis'' *'' P. daveyae'' *'' P. decipiens'' *'' P. decussata'' *'' P. delicatula'' *'' P. denudata'' *'' P. derbesii'' *'' P. deusta'' *'' P. devoniensis'' *'' P. dichotoma'' *'' P. dotyi'' *'' P. dumosa'' *'' P. echigoensis'' *'' P. echinata'' *'' P. elongata'' - lobster horns *'' P. elongella'' *'' P. erythraea'' *'' P. exilis'' *'' P. fernandeziana'' *'' P. fibrata'' *'' P. fibrillosa'' *'' P. figariana'' *'' P. flabelliformis'' *'' P. flabellulata'' *'' P. flexella'' *'' P. flexicaulis'' *'' P. flocculosa'' *'' P. foeniculacea'' *'' P. foetidissima'' *'' P. forfex'' *'' P. fracta'' *'' P. fragilis'' *'' P. fucoides'' *'' P. funebris'' *'' P. furcellata'' *'' P. fuscorubens'' *'' P. gonatophora'' *'' P. gracilis'' *'' P. guadalupensis'' *'' P. guernisacii'' *'' P. hancockii'' *'' P. hapalacantha'' *'' P. haplodasyae'' *'' P. hassleri'' *'' P. havanensis'' *'' P. havaniensis'' *'' P. hemisphaerica'' *'' P. hendryi'' *'' P. herpa'' *'' P. hirta'' *'' P. hochstetteriana'' *'' P. hockstetteriana'' *'' P. homoia'' *'' P. howei'' *'' P. implexa'' *'' P. incompta'' *'' P. indigena'' *'' P. infestans'' *'' P. isogona'' *'' P. japonica'' *'' P. johnstonii'' *'' P. kampsaxii'' *'' P. kappannae'' *'' P. kieliana'' *'' P. kotschyana'' *'' P. kowiensis'' *'' P. lanosa'' *'' P. letestui'' *'' P. macounii'' *'' P. marchantae'' *'' P. masonii'' *'' P. mollis'' *'' P. morrowii'' *'' P. mottei'' *'' P. muelleriana'' *'' P. namibiensis'' *'' P. nathanielii'' *'' P. neglecta'' *'' P. nhatrangense'' *'' P. nhatrangensis'' *'' P. nigra'' *'' P. nigrescens'' *'' P. nizamuddinii'' *'' P. opaca'' *'' P. ornata'' *'' P. orthocarpa'' *'' P. pacifica'' *'' P. paniculata'' *'' P. paradoxa'' *'' P. parthasarathyi'' *'' P. parvula'' *'' P. pentamera'' *'' P. perforans'' *'' P. pernacola'' *'' P. perriniae'' *'' P. platycarpa'' *'' P. plectocarpa'' *'' P. plectrocarpa'' *'' P. polychroma'' *'' P. polyspora'' *'' P. porrecta'' *'' P. propagulifera'' *'' P. pseudovillum'' *'' P. pulvinata'' *'' P. quadrata'' *'' P. ramentacea'' *'' P. requienii'' *'' P. rhododactyla'' *'' P. rhunensis'' *'' P. rigidula'' *'' P. rudis'' *'' P. saccorhiza'' *'' P. sadoensis'' *'' P. sanguinea'' *'' P. scopulorum'' *'' P. senticulosa'' *'' P. sertularioides'' *'' P. setigera'' *'' P. shepherdii'' *'' P. simplex'' *'' P. simulans'' *'' P. sinicola'' *'' P. sonorensis'' *'' P. sparsa'' *'' P. sphaerocarpa'' *'' P. spinosa'' *'' P. stricta'' *'' P. strictissima'' *'' P. stuposa'' *'' P. subtilissima'' *'' P. subulata'' *'' P. subulifera'' *'' P. succulenta'' *'' P. tapinocarpa'' *'' P. teges'' *'' P. tenerrima'' *'' P. tenuistriata'' *'' P. tepida'' *'' P. tokidae'' *'' P. tongatensis'' *'' P. tripinnata'' *'' P. triton'' *'' P. tsudana'' *'' P. tuberosa'' *'' P. tuticorinensis'' *'' P. unguiformis'' *'' P. upolensis'' *'' P. urbana'' *'' P. urbanoides'' *'' P. urceolata'' *'' P. utricularis'' *'' P. virgata'' *'' P. yonakuniensis''

Notes

References

External links

Images
of ''Polysiphonia'' at

Algaebase AlgaeBase is a global species database of information on all groups of algae, both seaweed, marine and freshwater algae, freshwater, as well as sea-grass. History AlgaeBase began in March 1996, founded by Michael D. Guiry, Michael Guiry. Text ...

* {{Taxonbar, from=Q610836 Rhodomelaceae Red algae genera