Polysiphonia | |
---|---|
Polysiphonia urceolata | |
Scientific classification | |
(unranked): | Archaeplastida |
Division: | Rhodophyta |
Class: | Florideophyceae |
Order: | Ceramiales |
Family: | Rhodomelaceae |
Genus: | Polysiphonia Greville, 1823 |
Polysiphonia, known as red hair algae, [1] is a genus of filamentous red algae with about 19 species on the coasts of the British Isles [2] and about 200 species worldwide, [3] including Crete in Greece, Antarctica and Greenland. [4] [5] Its members are known by a number of common names. [note 1] [4] It is in the order Ceramiales and family Rhodomelaceae. [6]
Polysiphonia is a red alga, polysiphonous [2] and usually well branched, with some plants reaching a length of about 30 cm. They are attached by rhizoids or haptera [5] to a rocky surface or other alga. The thallus (tissue) consists of fine branched filaments each with a central axial filament supporting pericentral cells. [7] The number of these pericentral cells (4–24) is used in identification. [8] [9] [10] Polysiphonia elongata [11] shows a central axial cell with 4 periaxial cells with cortical cells growing over the outside on the older fronds. [2] Its cuticle contains bromine. [12]
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. [4]
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. [2] Polysiphonia lanosa is commonly found growing on Ascophyllum nodosum. [13]
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. [14] [15] [ page needed ] Male (haploid) plants (the male gametophytes) produce spermatia and the female plants (the female gametophytes) produce the carpogonium (the haploid carpogonium) which remains attached to the parent female plant. After fertilization the diploid nucleus migrates and fuses with an auxiliary cell. A complex series of fusions and developments follow as the diploid zygote develops to become the carposporophyte, this is a separate phase of the life-cycle and is entirely parasitic on the female, it is surrounded by the haploid pericarp of the parent female plant. The diploid carpospores 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. [8] [ page needed ] [16] [ page needed ]
Chondrus crispus—commonly called Irish moss or carrageenan moss —is a species of red algae which grows abundantly along the rocky parts of the Atlantic coasts of Europe and North America. In its fresh condition it is soft and cartilaginous, varying in color from a greenish-yellow, through red, to a dark purple or purplish-brown. The principal constituent is a mucilaginous body, made of the polysaccharide carrageenan, which constitutes 55% of its dry weight. The organism also consists of nearly 10% dry weight protein and about 15% dry weight mineral matter, and is rich in iodine and sulfur. When softened in water it has a sea-like odour. Because of the abundant cell wall polysaccharides, it will form a jelly when boiled, containing from 20 to 100 times its weight of water.
Palmaria palmata, also called dulse, dillisk or dilsk, red dulse, sea lettuce flakes, or creathnach, is a red alga (Rhodophyta) previously referred to as Rhodymenia palmata. It grows on the northern coasts of the Atlantic and Pacific Oceans. It is a well-known snack food. In Iceland, where it is known as söl, it has been an important source of dietary fiber throughout the centuries.
Ulva lactuca, also known by the common name sea lettuce, is an edible green alga in the family Ulvaceae. It is the type species of the genus Ulva. A synonym is U. fenestrata, referring to its "windowed" or "holed" appearance, Despite the name, it is not a lettuce
In algal anatomy, a pit connection is a hole in the septum between two algal cells, and is found only in multicellular red algae − specifically in the subphylum Eurhodophytina, except haploid Bangiales. They are often stoppered with proteinaceous "pit plugs". By contrast, many fungi contain septal pores − an unrelated phenomenon.
Asparagopsis armata is a species of marine red algae, in the family Bonnemaisoniaceae. English name(s) include red harpoon weed. They are multicellular eukaryotic organisms. This species was first described in 1855 by Harvey, an Irish botanist who found the algae on the Western Australian coast. A. armata usually develops on infralittoral rocky bottoms around the seawater surface to around 40m of depth. Marine algae like A. armata are considered "autogenic ecosystem engineers" as they are at the very bottom of the food chain and control resource availability to other organisms in the ecosystem.
Red algae, or Rhodophyta, make up one of the oldest groups of eukaryotic algae. The Rhodophyta comprises one of the largest phyla of algae, containing over 7,000 recognized species within over 900 genera amidst ongoing taxonomic revisions. The majority of species (6,793) are Florideophyceae, and mostly consist of multicellular, marine algae, including many notable seaweeds. Red algae are abundant in marine habitats. Approximately 5% of red algae species occur in freshwater environments, with greater concentrations in warmer areas. Except for two coastal cave dwelling species in the asexual class Cyanidiophyceae, no terrestrial species exist, which may be due to an evolutionary bottleneck in which the last common ancestor lost about 25% of its core genes and much of its evolutionary plasticity.
Jania is a genus of red macroalgae with hard, calcareous, branching skeletons in the family Corallinaceae.
Polysiphonia lanosa is a common species of the red algae (Rhodophyta) often to be found growing on Ascophyllum nodosum.
Sirodotia Kylin (1912) is a genus of freshwater red alga which was described by Kylin in 1912, and placed in the Batrachospermaceae family.
Polysiphonia denudata is a small red alga, Rhodophyta, growing as tufts up to 20 cm long without a main branch axis.
Polysiphonia devoniensis is a species of marine algae. It is a small red alga in the Division Rhodophyta. It is a species new to science only described recently and first published in 1993.
Polysiphonia elongata is a small red marine algae in the Rhodophyta.
Polysiphonia fibrata is a species of Polysiphonia that grows as small dense tufted and finely branched marine alga in the Rhodophyta.
Polysiphonia fibrillosa (Dillwyn) Sprengel is a species of marine red alga in the Rhodophyta.
Polysiphonia foetidissima Cocks ex Bornet is small red marine alga in the Rhodophyta.
Polysiphoides fucoides (Hudson) Greville is a common marine alga in the Division Rhodophyta.
Polysiphonia furcellata (C.Agardh) Harvey is small marine red alga in the Division Rhodophyta.
Choreocolax polysiphoniae is a minute marine parasitic alga in the division Rhodophyta.
Polysiphonia stricta is a small red marine alga in the Division Rhodophyta.
Vertebrata fruticulosa(Boergeseniella fruticulosa Kylin) is a small marine alga in the Division Rhodophyta.
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