Brown algae

from Wikipedia, the free encyclopedia
Brown algae
Sawwrack (Fucus serratus)

Sawwrack ( Fucus serratus )

Systematics
Classification : Creature
Domain : Eukaryotes (eukaryota)
without rank: Diaphoreticks
without rank: Sar
without rank: Stramenopiles (stramenopiles)
without rank: Brown algae
Scientific name
Phaeophyceae
FR Kjellman
Desmarestia aculeata , Desmarestiales
Padina pavonica , Dictyotales
Colpomenia peregrina , Ectocarpales
Knotwrack ( Ascophyllum nodosum ), Fucales
Sugar wrack , fingertrack and palm wrack , laminariales
Halopteris filicina , Sphacelariales
Saccorhiza polyschides , Tiliopteridales

The brown algae (Phaeophyceae) form a separate group within the Stramenopiles (Stramenopiles), a subgroup of the Sar . It is mostly marine, often brown, algae with a generation change .

A characteristic of these thread-like or leaf-like algae, which are definitely multicellular, are the brown fucoxanthin dyes that mask the green chlorophyll .

features

The brown algae are a very diverse group. The habitus ranges from small, branched cell threads, thread thalli, pseudoparenchymatic thalli to complex, multi-layered protoctists several meters in size with tissue and organ differentiation. The organs of this seaweed are reminiscent of the leaf, axis and root of the cormophyte and are called phylloid , cauloid and rhizoid by analogy . Unicellular organisms are absent from brown algae.

Plastids

Like all heterocontact algae, brown algae have complex plastids (also called chromatophores ) without nucleomorphs , which are the result of secondary endosymbiosis . The photosynthetic pigments are those of the hetero accounts: chlorophyll a, c 1 and c 2 . The accessory pigments are β- carotene , fucoxanthin and, to a lesser extent, diadinoxanthin and diatoxanthin (both like fucoxanthin xanthophylls ). Usually there is only one chromatophore per cell, rarely several. The DNA is arranged in a ring-type genophore . The reserve polysaccharide is chrysolaminarin .

Scourges

The single-cell swarmers of the brown algae ( zoospores and gametes ) have the two differently shaped flagella ("heterokont") typical of the stramenopiles. The base of the dragging whip is swollen and may serve as a photoreceptor. It is near the eye spot, a reddish brown spot in the chromatophore. The drag whip always has a thin hair extension at the end, the pull whip sometimes. This feature occurs only here and in the Xanthophyceae .

Cell wall

In addition to cellulose, the cell walls of brown algae contain alginates as the main structural components. The cellulose forms the fibrillar part that ensures the strength of the cell walls. The fibrils are embedded in an amorphous, slimy substance that consists of alginates dissolved colloidally in water . Insoluble alginate gels provide additional reinforcement . This cell wall structure, which is specific to the brown algae, enables strength and flexibility at the same time, in order to be able to withstand the mechanical loads caused by the tidal currents and the wave movements.

Multiplication

The brown algae are changing generations . The meiospores are formed in unilocular (single-chambered) sporocysts , the gametes in plurilocular (multi-chambered) gametangia . The generation change is heterophasic, i. H. It alternate haploid and diploid from generations. Within the brown algae there is a developmental line from a similar (isomorphic) generation change to a reduction of the haploid gametophyte: heteromorphic (differently shaped) generation change. With the Fucales , the haploid generation is almost completely regressed, so that they are almost pure Diplonts .

In the gametes there is a line of development from similarly shaped gametes ( isogamy ) via flagellated gametes of different sizes ( anisogamy ) to non-flagellated female egg cells ( oogamy ).

Occurrence

Most species live in the sea. Only five genera are known to be freshwater inhabitants. They develop the greatest diversity in the temperate and cold latitudes of the oceans. They live as part of the benthos and are grown as lithophytes on rocks, stones and the like. Some are exposed at low tide or also grow epiphytically on other algae. In some areas, such as the American Pacific coast, they form large undersea forests ( kelp forests ). The giant seaweed Lessonia , Macrocystis and Nereocystis grow here . Smaller forms grow on stones, barnacles, snails and algae. Some species even grow endophytically in larger algae.

Systematics

The brown algae are a group of stramenopiles . Your sister group is likely to be a clade consisting of Xanthophyceae , Pinguiochrysidales and Phaeothamniophyceae .

The taxon Phaeophyceae was established in 1891 by Frans Reinhold Kjellman with the rank of a class (in: The natural plant families , part 1, division 2. (Engler, A. & Prantl, K. Eds), pp. 176-181. Engelmann, Leipzig ).

The brown algae include around 1850 species. The internal system was initially based in many cases on a classification according to the life cycle, but has been in a state of upheaval since around 1990 due to molecular genetic studies. Adl et al. (2012) divided the Phaeophyceae into 19 unrestricted subgroups (formerly orders ). Silberfeld & al. (2014) summarized all phylogenetic research results in a new classification for the first time . Then the 304 genera of brown algae can be grouped into four large family groups (subclasses) with 18 orders (species numbers according to AlgaeBASE 2014):

  • Discosporangiophycidae Silberfeld, F. Rousseau et Reviers, with the only order
    • Discosporangiales OCSchmidt emend. H. Kawai, Hanyuda, Draisma & Müller, with 3 species
  • Ishigeophycidae Silberfeld, F. Rousseau et Reviers, with the only order
  • Dictyotophycidae Silberfeld, F. Rousseau et Reviers, with about 353 species
  • Fucophycidae Cavalier-Smith, with about 1477 species

The assignment of 7 species of the genera Jonssonia , Porterinema , Sorapion and Zosterocarpus is still unclear .

Northeast Atlantic species (selection)

Some more common north-east Atlantic species are:

For the brown algae that occur in the German Bight, see the list of marine algae from Heligoland .

use

Burning of seaweed in Brittany
Algae oven in Finistère
Harvest of Lessonia trabeculata

Alginates are obtained from brown algae and are used as gel formers . Alginates are a by-product in the extraction of iodine from seaweed using the wet process. Because of the wide range of possible applications, alginates are also extracted directly from brown algae for use in the food, pharmaceutical and cosmetic industries. Brown algae of the Macrocystis , Laminaria , Ascophyllum , Sargassum , Ecklonia , Lessonia and Durvillea genera are harvested using trawlers .

Some species are also eaten, such as kombu ( Saccharina japonica and other saccharina species), wakame ( Undaria pinnatifida ), and cochayuyo ( Durvillaea antarctica ).

Seaweed has been burned in France since the 17th century to extract calcium , iodine and alkali- rich ashes for the glass and soap industries . The stone- framed fireplaces are called algae stoves or kelp stoves (from English: kelp ). In 1719, James Fea introduced algae burning to Orkney . The shallow coastal water and the long coastline make the northern islands of the Orkney, especially North Ronaldsay , Sanday and Stronsay , ideal places for seaweed extraction. The seaweed was cut from the rocks at low tide or collected on land after storms. At the top of production, Orkney produced more than 3,000 tons of seaweed annually. The kelp boom lasted 50 years (from 1780 to 1830). When iodine was in demand in the 1840s, the kelp industry reawakened at a lower level.

literature

Individual evidence

  1. ↑ Christiaan van den Hoek, Hans Martin Jahns, David G. Mann: Algen . 3. Edition. Thieme, Stuttgart 1993, ISBN 3-13-551103-0 , p. 136 .
  2. ^ Robert A. Andersen: Biology and systematics of heterokont and haptophyte algae . in: American Journal of Botany. Columbus 91.2004, pp. 1508-1522, ISSN  0002-9122
  3. ↑ a b Michael D. Guiry, GM Guiry: Phaeophyceae In: AlgaeBASE - World-wide electronic publication, National University of Ireland, Galway , accessed November 9, 2014.
  4. ↑ Sina M. Adl, Alastair GB Simpson a. a .: The Revised Classification of Eukaryotes. Journal of Eukaryotic Microbiology , 59: 457-458, 2012, PDF Online
  5. ↑ Thomas Silberfeld, Florence Rousseau, Bruno de Reviers: An Updated Classification of Brown Algae (Ochrophyta, Phaeophyceae). In: Cryptogamie, Algologie, 35 (2): pp. 117-156. 2014.
  6. ↑ P. Kornmann, PH Sahling: Sea algae from Helgoland - Benthic green, brown and red algae. Biological Institute Helgoland, Hamburg 1983, ISSN  0017-9957
  7. ↑ Michael Guiry: The Seaweed Site: information on marine algae: NE Atlantic seaweeds , accessed March 11, 2012.
  8. ↑ Sigurd Towrie: Kelp Burning in Orkney , orkneyjar.com, Orkneyjar, the heritage of the orkney islands, 1996–2019, accessed September 24, 2019.
  9. ↑ kelp = Tang and Tangasche (= the kelp ), dict.leo.org, accessed September 24, 2019
  10. ↑ Hamish Haswell-Smith, Hamish: The Scottish Islands. Canongate, Edinburgh 2004, ISBN 1-84195-454-3 .
  11. ↑ Friedrich Lütke Twenhöven: The use of algae. In: Studium Biologie, 1997, p. 41. ( Online ; PDF; 72 kB).

Web links

Commons : Brown Algae  - Collection of images, videos and audio files