Ulva (genus)

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Ulva
Ulva californica

Ulva californica

Systematics
without rank: Chloroplastida
without rank: Chlorophyta
without rank: Ulvophyceae
Order : Ulvales
Family : Ulvaceae
Genre : Ulva
Scientific name
Ulva
L. , 1753
Flat intestinal kelp ( Ulva compressa )
Common intestinal wrack ( ulva intestinalis )
Wavy bowel tang ( ulva linza )
Sea lettuce ( ulva lactuca )

Ulva is a genus of multicellular green algae that is distributed in the seas with around 130 species. The thallus consists of two cell layers and is tubular to leaf-like in shape, whereby the species can differ greatly morphologically. Itis attached to a baseby a rhizoid . The best-known type is the sea ​​lettuce Ulva lactuca .

The genus Ulva was from the section Phykologie in the German Botanical Society for the algae of the year chosen, 2015.

description

The algae reach a length of a few centimeters to over a meter ( Ulva expansa even up to three meters). They are anchored to the ground with an adhesive organ ( rhizoid ), and after storms they can occasionally be found floating freely. The green thallus is flat and leaf-like-membranous or sack-like to tubular and hollow. Some species have perforations on the surface. The edge of the thallus can be smooth, curled, or toothed.

The individual species are extremely diverse and can vary in appearance depending on their location. Therefore microscopic examinations are necessary for a reliable identification of the species.

The thallus consists of two closely spaced layers of cells. The vegetative cells each contain a chloroplast and nucleus, while Rhizoidzellen often multinucleate are.

Reproduction

A diplohaplontic generation change is typical , whereby the haploid gametophytes and the diploid sporophytes cannot be distinguished externally (isomorphic). No special reproductive organs are formed, but every cell with the exception of the rhizoid cells and some neighboring basal cells can form gametes or zoospores . The gametophytes are unisexual, either female or male. The gametes have two flagella and are anisogamous in most species; H. the females are larger than the males. They are released individually through pores on the top of the thallus and strive for light (positive phototaxis ). The zygote resulting from their union goes over to negative phototaxis, attaches to a substrate and grows into a sporophyte. When the spores are formed, meiosis occurs , making them haploid again. They have four flagella and show first a positive and later a negative phototaxis.

After the zygote or spore has settled, the alga initially grows in the form of threads. The leaf-like thallus finally arises over a tubular stage, as the tube, which consists of one layer of cells, flattens out to form a two-layer surface.

Symbiosis with bacteria

Algae of the genus Ulva live in symbiosis with bacteria, without which they can hardly grow and only form a misshapen cluster of cells. In U. mutabilis , two genera of bacteria have been identified whose presence enables the alga to develop normally : in the presence of Roseobacter , the leaf-like thallus is formed, and Cytophaga enables the formation of rhizoids. The bacteria also use signal substances to attract the flagellated zoospores of the alga to colonize. They live in a biofilm on the surface of the alga.

Systematics and distribution

The genus Ulva was established by Carl von Linné in Species Plantarum 2 in 1753 . The type species is Ulva lactuca L. The tubular representatives of the genus were separated in 1820 by Heinrich Friedrich Link as a separate genus "Darmtange" ( Enteromorpha ). Since 2003 they have been part of Ulva again . According to AlgaeBase, the genus comprises 131 species.

The genus is distributed worldwide on all sea coasts. Some species occur as cosmopolitans from polar to tropical regions. Inland waters with lower salinity are also sometimes populated.

The following species have been identified in the German coastal waters of the North Sea and the Baltic Sea :

use

Several types are consumed as traditional foods , especially in East Asia . In Japan, Ulva - and Monostroma -Algen in dried form as Aonori known.

Web links

Commons : Ulva  - collection of images, videos and audio files

Individual evidence

  1. ↑ a b Sea lettuce Ulva only comes with the right bacteria in the form of press release, Phycology Section of the German Botanical Society (DBG), from January 5, 2015.
  2. ↑ a b c d e f g h i j k Wolfram Braune: Marine algae. A color guide to the common benthic green, brown and red algae of the world's oceans . Ruggell: Gantner, 2008, ISBN 978-3-906166-69-8 , p. 36 (-43).
  3. ↑ a b c d e f g h i j Michael D. Guiry in Michael D. Guiry, GM Guiry: Ulva Linnaeus, 1753, nom. et typ. cons., In: Algaebase - World-wide electronic publication, National University of Ireland, Galway, accessed on June 29, 2018. ( http://www.algaebase.org/search/genus/detail/?genus_id= k3ba340f74367f9dd )
  4. ↑ Thomas Wichard: Exploring bacteria-induced growth and morphogenesis in the green macroalga or Ulvales (Chlorophyta) . Frontiers in Plant Science 6 : 86, March 3, 2015.
  5. ↑ Carl von Linné: Species Plantarum. 1753, Volume 2, p. 1163 .
  6. ↑ Hillary S. Hayden; Jaanika Blomster; Christine A. Maggs; Paul C. Silva; Michael J. Stanhope & J. Robert Waaland: Linnaeus was right all along: Ulva and Enteromorpha are not distinct genera . European Journal of Phycology. British Phycological Society. Issue 38 (3): pp. 277-294. 2003. doi: 10.1080 / 1364253031000136321
  7. ↑ Dirk Schories, Uwe Selig, Hendrik Schubert: Species and synonym list of the German marine macroalgae based on historical and recent records (list of species and synomes of macroalgae in German coastal waters - evaluation of historical and recent findings) . In: Rostock. Marine biologist Contribution ., Issue 21, 2009, pp. 34-37. PDF file
  8. ↑ Ole G. Mouritsen, Prannie Rhatigan, José Lucas Pérez-Lloréns: World cuisine of seaweeds: Science meets gastronomy . In: International Journal of Gastronomy and Food Science . tape 14 , 2018, p. 57 , doi : 10.1016 / j.ijgfs.2018.09.002 (English).