Crab claw

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Crab claw
Crab claw (Stratiotes aloides)

Crab claw ( Stratiotes aloides )

Systematics
Class : Bedecktsamer (Magnoliopsida)
Monocots
Order : Frog-spoon-like (Alismatales)
Family : Frog bite family (Hydrocharitaceae)
Genre : Stratiotes
Type : Crab claw
Scientific name
Stratiotes aloides
L.

The crab claws ( Stratiotes aloides ; old names are: Stratiotes aquatica , Stratiotes potamios , Militaris aizoides , Sedum aquatile , Aloe palustris ) is a species of aquatic plant from the frog-bite family (Hydrocharitaceae). It is the only recent representative of the genus Stratiotes . In the Tertiary it also included other species that were found in Central Europe at that time .

features

It was named after the bracts of the stems, which are reminiscent of the claws of a crab (center)
Female flower
Mass development through formation of runners in a brackish meadow in the Elbe valley

The plant forms up to 40 centimeters large, rosette-shaped leaves , some of which protrude from the water during the growing season. The funnel-shaped growth form is reminiscent of an aloe , with the leaves up to four centimeters wide, triangular and hooked, sawn forward. The bracts of their stems look like crayfish claws. Due to the intensive formation of runners in the leaf axils, the individual rosettes under the water surface are connected to one another to form large units. The plant drives dense clusters of long, unbranched water roots down, which absorb nutrients from the free water. The flowers reach a diameter of three to four centimeters and consist of three white crown- and three green sepals ; the center with the reproductive organs is yellow. The species is dioecious ; so there are male and female plants. The flowering period extends from May to July. The egg-shaped, hexagonal fruit is up to 3.5 centimeters long. More important than the spreading via seeds is the vegetative propagation via runners. In late autumn the plants sink to the bottom of the water and only rise again in spring.

The chromosome number of the species is 2n = 24.

Occurrence and endangerment

Crayfish claws grow in floating leaf communities that are warm, sheltered from the wind, muddy, mesotrophic to eutrophic , base-rich, non-polluted and mostly stagnant waters of the floodplains, for example in backwaters, ditches, ponds and canals. The species is distributed Eurasian-continental from Europe (except the southern part / Mediterranean area) to Central Asia. It is a character species of the association Hydrocharitetum morsus-ranae from the Lemnion association. In the north German lowlands it occurs scattered, with accumulations in the floodplains of the lower reaches of larger rivers. One such focus is the Bremen / Wesermarsch area, for example . Crab claws are rare in the hilly and mountainous regions and are absent for long stretches. It is on the Red List of Endangered Species and is “specially protected” in terms of the law ( BArtSchV , Federal Species Protection Ordinance ). The plant is sensitive to strong fluctuations in the water level and to contamination. It occurs up to 2 meters deep. Their stocks are also being decimated by measures for water maintenance (ditch clearance, pond management). Some anglers illegally remove floating carpets that are annoying to them.

particularities

The plants, which like to grow very socially when they are found, only float on the water surface during the summer months. In autumn the rosettes sink to the bottom of the water and form winter buds ( turions ); the outer leaves die off. In the coming spring, the winter buds rise to the surface and form new plants there. But the heart of old rosettes also floats on the bottom after wintering and continues to grow. The strong biomass production of large deposits has a silting-up (sludge-forming) effect in water bodies. The species is spread by floods. Where it was common, it was previously used as pig feed and, because of its high phosphorus and potassium content, for green manure .

The dragonfly species, the green damsel, has specialized entirely in the crayfish claw when laying eggs and is therefore tied to its occurrence.

In 1998 the crab claws were named flower of the year . It is also a popular ornamental plant for garden ponds.

Names

Crab claw together with tri-furrow duckweed
Single rosette in the Schwaanhavel

Other, sometimes rare German names are: Agel , water blessing or water saw , sack , sickle water , sickle herb or saber herb (after the pointed shape of the leaves), water scissors or scissors , crab claw (like crab claws probably because of the "scissor-like sheaths of the inflorescences "), Pickerel weed (name of various aquatic plants, between which like should stop pike), water , marsh or Afteraloe (physical resemblance with some Aloe species, just hence the species name aloides ), Reiter herb (perhaps Greek. στρατιώτης ( stratiṓtes) 'soldier, warrior' ajar ); The terms water feather (otherwise Hottonia palustris ) and water fennel (otherwise Oenanthe ; for the plant treated here also Falscher or Donnerbart water fennel ) have been taken over entirely from other plants . The name Stratiotes (potamios) itself is transferred from a plant found on the Nile (probably Pistia stratiotes ), which Pliny the Elder and the military doctor Dioscurides describe as a wound healing agent.

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literature

  • Eckhard Garve: Atlas of the endangered fern and flowering plants in Lower Saxony and Bremen. In: Nature conservation, landscape conservation, Lower Saxony. 30. 1994, ISBN 3-922321-68-2
  • Henning Haeupler , Thomas Muer: picture atlas of the fern and flowering plants of Germany (= the fern and flowering plants of Germany. Volume 2). Published by the Federal Agency for Nature Conservation. Ulmer, Stuttgart 2000, ISBN 3-8001-3364-4 .
  • Elfrune Wendelberger: Plants of the wetlands. BLV-Intensivführer, Munich 1986, ISBN 3-405-12967-2

Individual evidence

  1. ↑ a b c Erich Oberdorfer : Plant-sociological excursion flora for Germany and neighboring areas . 8th edition. Stuttgart, Verlag Eugen Ulmer, 2001. Pages 113–114. ISBN 3-8001-3131-5
  2. ↑ Rafaël Govaerts (Ed.): Stratiotes. In: World Checklist of Selected Plant Families (WCSP) - The Board of Trustees of the Royal Botanic Gardens, Kew . Retrieved June 20, 2018.
  3. ^ Pliny, Naturalis historia XXIV , 169.
  4. ^ Dioscurides, De materia medica IV, 100 (102), German translation with annotations: Prof. Dr. J. Berendes, Stuttgart 1902, p. 424  ( Page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. .@1@ 2Template: Toter Link / www.heilpflanze-welt.de  
  5. ^ Heinrich Marzell / Heinz Paul, Dictionary of German Plant  Names IV, Stuttgart / Wiesbaden 1979 (Cologne 2000, reprint), p. 516ff.

Web links

Commons : Crab claws ( Stratiotes aloides )  - Collection of pictures, videos and audio files