Fingertang
| Fingertang | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Fingertrack ( Laminaria digitata ) |
||||||||||||
| Systematics | ||||||||||||
|
||||||||||||
| Scientific name | ||||||||||||
| Laminaria digitata | ||||||||||||
| ( William Hudson ) Jean Vincent Felix Lamouroux |
.jpg)
The fingertip ( Laminaria digitata ) is a type of brown algae from the order of the Laminariales . It forms extensive stocks ( seaweed forests ) on the coasts of the North Atlantic and is also found in the North Sea and Baltic Sea. It is used economically to obtain alginate .
description
The fingertrack is a stately, perennial seaweed with a palm-like habit that can be more than 2 m long. The sporophyte is attached to the rocky subsoil with a strong claw-like adhesive organ ( rhizoid ). Above this, the thallus is divided into a stalk ( cauloid ) and a leaf-like surface ( phylloid ) and has differentiated tissue.
The stem is flattened, elastic and has a smooth surface that is usually free of epiphytes. The length of the stem reaches about 20 to 40 cm, depending on the populated water depth, its diameter is about 2 cm. It consists of a layer of bark and a central body in which real conduction paths run. The brown to dark brown, leathery, coarse phylloid with a length of up to 1.5 m and a width of up to 50 cm is divided into fingers and widens directly above the stem without a border.
The finger wrack differs from the similar palm wrack ( Laminaria hyperborea ) by its flattened, flexible, smooth stem as well as the darker leaf surface with gradually widening leaf base. In addition, the rhizoid is not conical.
Leaf change
The leaf of the fingertip is renewed every year. The reserve substances stored in the old leaves are transported to the growth zone as early as winter. With increasing light, a new phylloid grows from the leaf base in spring, on which the previous year's leaf still sits until the beginning of May, while it degenerates at the ends.
development
In the fingertang there is a generation change with two very different generations. The visible seaweed is the diploid sporophyte . From June to October, the tubular sporangia are formed on the phylloid in irregular darker spots ( sori ). In each sporangium , 32 mobile zoospores arise through meiosis . These grow into the haploid gametophyte , which consists of microscopic, branched cell threads. The egg cells and spermatozoids are formed here, triggered by blue light and low temperatures. The spermatozoids are attracted to the egg cell by the pheromone lamoxiren . After fertilization, the zygote settles and germinates into a young sporophyte. The young plants become fertile for the first time at two or three years of age .
ecology
The optimum growth of the fingertip is (5) 10 to 17 ° C, so the species is adapted to cold temperate seas. In the extremely warm summers of 2003 and 2006, no meiospores were released near Heligoland, although Sori were present. Therefore, the decline in laminariums that can be observed in many places is viewed as a consequence of global warming .
Sea urchins of the genus Strongylocentrotus , which have reproduced en masse after overfishing , can eat and completely destroy entire stocks of the fingertip, leaving only the bare bottom. The gray top snail ( Gibbula cineraria ), the banded pit snail ( Lacuna vincta ) and the woodlouse Idotea granulosa also eat the fingerwrack. Since they prefer the Sori to the vegetative structures and are also often found in masses, they can severely impair the reproduction of the fingertip.
Occurrence
The fingertrack is widespread off the coast of the North Atlantic . In Europe it can be found from Iceland and Spitzbergen to Spain and the Canary Islands . It can also be found on suitable substrates in the North Sea and Baltic Sea , for example near Helgoland . It also grows off Greenland and on the Atlantic coast from North America to Cape Cod .
It inhabits the upper sublittoral and forms dense seaweed forests or lower "seaweed meadows" on rocky ground . In the North Sea it grows to a depth of 1.5 m below the low water line. When the water level is very low, the stocks can be exposed for a short time.
Systematics
The fingertang was first described in 1762 by William Hudson under the name Fucus digitatus (In: Flora anglica , p. 474). John Vincent Felix Lamouroux placed the species in the genus Laminaria in 1813 (In: Essai sur les genres de la famille des thalassiophytes non articulées . Annales du Muséum d'Histoire Naturelle, Paris 20, p. 42). This is the type species of the genus Laminaria (lectotype).
Synonyms for Laminaria digitata (Hudson) JVLamouroux are Fucus digitatus Hudson, Gigantea digitata (Hudson) Stackhouse, Hafgygia digitata (Hudson) Kützing and Saccharina digitata (Hudson) Kuntze. Other synonyms are Laminaria apoda Postels & Ruprecht, Laminaria conica Bory de Saint-Vincent, Laminaria cucullata (Le Jolis) Foslie, Laminaria ensifolia Kützing, Laminaria flexicaulis Le Jolis, Laminaria intermedia Foslie, Laminaria latifolia C. Agardh , Laminaria phycodendron De la Pylaie and Laminaria stenophylla (Harvey) J. Agardh.
Laminaria digitata belongs to the Laminariaceae family within the order of the Laminariales .
use
In the past, the seaweed washed up or harvested when the water was low was used as fertilizer . In the Middle Ages, the incineration of algae (kelp) was of economic importance in order to extract alkalis , which were needed for soap and glass production . Seaweed incineration later flourished again to produce iodine . The iodine content of the fingertip is 0.25 to 5% of the dry matter.
Today fingertang is harvested in France ( Brittany ) for the production of alginate . A harvest of 75,000 t is stated for 2005.
In Ireland and France, fingertang is also used to a lesser extent to produce seaweed vegetables. The content of minerals and trace elements, especially potassium (0.116 mg per g dry weight) and calcium (10.05 mg per g dry weight) is higher than that of most edible land plants. However, the protein content is relatively low at 8 to 15% of the dry matter.
swell
- P. Kornmann, PH Sahling: Sea algae from Helgoland - Benthic green, brown and red algae. Biological Institute Helgoland, Hamburg 1983, ISSN 0017-9957 , pp. 144-149. (Sections description, leaf change, development, occurrence, use)
- 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 , pp. 194-195. (Sections Description, Occurrence, Use)
Individual evidence
- ↑ a b c Michael Guiry: The Seaweed Site: information on marine algae: Laminaria digitata , accessed April 12, 2012.
- ↑ a b c d e f g Inka Bartsch, Christian Wiencke, Kai Bischof, Cornelia M. Buchholz, Bela H. Buck, Anja Eggert, Peter Feuerpfeil, Dieter Hanelt, Sabine Jacobsen, Rolf Karez, Ulf Karsten, Markus Molis, Michael Y Roleda, Hendrik Schubert, Rhena Schumann, Klaus Valentin, Florian Weinberger & Jutta Wiese: The genus Laminaria sensu lato: recent insights and developments . In: European Journal of Phycology , 43: 1, 2008, pp. 1–86 ( doi : 10.1080 / 09670260701711376 )
- ^ A b c Michael D. Guiry, GM Guiry: Laminaria digitata. In: Algaebase - World-wide electronic publication, National University of Ireland, Galway , accessed April 12, 2012.
