Water trap ( Aldrovanda vesiculosa )
|Scientific name of the genus|
|Scientific name of the species|
The water trap is the only recent species in the monotypic genus Aldrovanda . However, there are other fossil species in this genus. There are significant geographical differences within the species. B. the Australian form neither a winter dormancy due to Turionen , nor is it frost hardy.
The plant becomes about 10 to 30 cm long. Along the stem axis are five to nine 2 to 3 mm long catch leaves at short intervals in a whorl-shaped arrangement on a petiole, which Diels characterizes as an "extended leaf base ". The leaf base contains several air-filled cavities that provide most of the plant's buoyancy. The plant grows on one side and dies on the other end; under good conditions, one or two whorls are formed per day.
With its catch leaves, a folding trap similar to a smaller version of the Venus fly trap , the water trap catches small animals , preferably water fleas , but also, for example, young mosquito larvae . At the edge of the trap there are four to six noticeably stiff bristles; the inside of the trap is also finely haired with sensitive hairs. These are sensory hairs that cause the two halves of the leaf blade to close in a maximum of 1/50 of a second, whereby the catch is only possible in warm water temperatures (from around 20 ° C). Once the trap has caught a prey, it is broken down with the help of digestive juices.
The small, white flower of the water trap rises on short stems above the surface of the water; it only stays open for a few hours. The subsequent formation of the seed capsule, however, takes place again under water. The seeds germinate cryptocotylar , that is, the cotyledons remain within the seed and absorb its reserves, the so-called endosperm . However, the water trap rarely blooms - at least in temperate conditions.
The water trap usually reproduces vegetatively . In addition, the plant branches out strongly during its growth phase. The subsequent death of the main shoot results in independent individuals. Since the plant is vigorous, numerous individuals can emerge quickly.
A second method of vegetative propagation, which only occurs in winter-hardy forms, is that by so-called turions as part of the wintering strategy of the plant. At the end of the growing season, leaf whorls detach from the tip of the shoot and sink to the bottom of the water due to the high weight and the emission of gases. The turions are frost hardy down to −15 ° C. With the new start of growth in spring, the turions rise again and start growing again.
The number of chromosomes is 2n = 48.
Distribution and habitat
The water trap is the most widespread species of carnivore , because it is native to Europe , Asia , Africa and Australia . However, it is rare in all of its areas. The species spreads via epichory : it adheres to the plumage of waterfowl, which it then takes to other waters. As a result, the water trap is often found along bird migration routes .
The water trap needs extremely clean, shallow, light and warm stagnant water that is both nutrient-poor and slightly acidic ( pH value around 6). It can be found floating freely between rushes or reeds , but also rice . As the vegetation in its area becomes increasingly dense, the water trap recedes and reappears in other places. It is sensitive to algae infestation .
The water trap thrives in companies of the Hydrocharition Association.
Endangerment and Status
In European countries the water trap is rare, critically endangered or already extinct. It is often viewed here as a tertiary relic. 200 years ago there were 150 locations; currently only a little under forty are known, mostly in Eastern and Southeastern Europe (e.g. 10 in Poland , 1 in Hungary , 1 in Romania , and a few in former Yugoslavia , Bulgaria , Ukraine and Russia ). In the last 30 years the species became extinct in Europe in France , Italy , Slovakia , Austria ( Lake Constance ) and Germany . The observed decline in the water trap is generally due to civilization-related eutrophication (increase in nutrient supply) of their waters.
In Germany it is found again in Brandenburg and Worms ; however, the stocks there are considered to have been anointed ; officially it has been extinct since 1986. Some stocks also exist in Switzerland , where they are actually not native; these locations go back to anointings from 1908. Nevertheless, they are strictly protected, among other things because they are traced back to the stocks from Lake Constance, which in Germany itself became extinct.
Little is known about detailed locations of the plant in Africa. Reported occurrences extend from northeast Africa to central ( Sudan , Uganda , Rwanda , Tanzania , Zimbabwe , Mozambique ) and South Africa (e.g. the Okavango Delta in Botswana ). Due to the comparatively undisturbed African flora and the low level of agriculture on the continent, endangerment of the species there is to be regarded as unlikely.
The species is strictly protected in Australia and all European countries where it still exists.
The evolution of the genus can be traced back a long way on the basis of fossil seed and pollen finds . In the mid-1980s, seed fragments of a species from the end of the Cretaceous period were found in today's Czech Republic , which were interpreted as the oldest known predecessor of the genus and at the same time represented the second oldest fossil find of a carnivorous species. The plant described as Palaeoaldrovanda splendens would have been a contemporary of the dinosaurs and would have lived under tropical conditions. A study from 2010 showed, however, that the supposed seed fragments cannot be assigned to a closely related Droseraceae, but that it is very likely that they are the fossil eggs of an insect .
The mass extinction triggered by 65 million years ago at the Cretaceous-Tertiary boundary did not impair the further growth of this genus. Almost twenty other species are known from the early Cenozoic . Already in the Eocene they separated into the sections Aldrovanda, Obliquae and Clavatae. Whether warm or cold periods followed, the genus always remained present with several species. Even in the Pleistocene , the Ice Age that preceded our present , six species can still be identified, of which only A. vesiculosa has survived to the present.
Since only seeds or pollen are fossilized due to the low mass of the plants , it is hardly possible to make a statement about the earlier shape of the plants. The so far unique find of a fossil leaf of an approximately 6 million year old Aldrovanda inopinata from the Miocene was all the more important . This find was made in Wackersdorf in 1963 . The leaf is very similar to that of the present species; An important difference, however, is the lack of sensitive hairs in the center of the leaf blade.
The water trap was discovered in 1699 by Leonard Plukenet in India , who named it Lenticula palustris Indica . It received its current scientific name in 1747 from Giuseppe Monti , who described Italian specimens and named them Aldrovand i a vesiculosa in honor of the Italian scholar Ulisse Aldrovandi . When Carl von Linné took over the name in 1753, however, the first "i" of the name was lost. It was first detected in Germany in 1846 in a pond in Pleß (Pszczyna) in Upper Silesia by Emanuel Friedrich Hausleutner .
Charles Darwin also made a distinction between the tropical and subtropical forms of the water trap and the tempered form under the names Aldrovanda vesiculosa var. Australis Darwin and Aldrovanda vesiculosa var. Verticillata . This system has been deviated from; Nowadays, despite different growth forms, all water traps are listed as one taxon.
Like all carnivorous plants, the water trap is the subject of interest from collectors. In the 1990s, the species was increasingly included in collections after Australian types were imported, whose tropical or subtropical habit enabled cultivation under uniform conditions without winter dormancy. However, their permanent culture is still considered difficult, also because of the aquatic attitude and their special requirements.
A stylized water trap is the symbol of the German Society for Carnivorous Plants .
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- Water falls. In: FloraWeb.de.
- Distribution map for Germany. In: Floraweb .
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- Distribution in the Netherlands  (Dutch)
- Thomas Meyer: Data sheet with identification key and photos at Flora-de: Flora von Deutschland (old name of the website: Flowers in Swabia )
- Carnivorous Plants Society page on the Waterfall
- The Aldrovanda Project - English-language research site with numerous additional information
- Aldrovanda vesiculosa inthe IUCN 2013 Red List of Threatened Species . Posted by: Cross, A., 2012. Retrieved September 7, 2013.