River pearl mussel
| River pearl mussel | ||||||||||||
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Margaritifera margaritifera |
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| Scientific name | ||||||||||||
| Margaritifera margaritifera | ||||||||||||
| ( Linnaeus , 1758) |
The freshwater pearl mussel ( Margaritifera margaritifera ) is one of the great freshwater - shells , as is true in Germany of the early 21st century extinction endangered species.
Species and development
According to the latest results, the freshwater pearl mussel can reach an age of up to 280 years. Size and age increase towards the north, so in Spain it is usually only 8–10 cm tall and around 60–70 years old, while in Sweden it is up to 280 years old and 14 cm tall. Their propagation is a complex process, as it is linked to demanding requirements, is susceptible to failure and has several intermediate stages. After the tiny early forms ( glochidia ) of the mussel have hatched, they need the brown trout as host , in whose gills they live parasitically for ten months ; In addition to the brown trout, only the huchen and, in Northern Europe, the Atlantic salmon are suitable. They grow from approx. 0.05 mm to 0.5 mm large young mussels. Around May, when the temperature and the stream bed are suitable, they let themselves fall in the river bed between the pebbles and stones at the bottom of the water and burrow there. There they live hidden and only come to the surface of the water bed after about seven years, in the fully grown stage and with the hard shell that has now formed. They then spend the rest of their lives largely stationary. In the current, they let the water flow through their gills and filter out food particles. The freshwater pearl mussel forms colonies in an ecologically intact environment.
The large river mussels, including the river pearl mussel, are also known as naiads .
Distribution area and history
The pearl mussel is found almost everywhere in the northern hemisphere, in Europe e.g. B. from Spain to northern Scandinavia (Arctic Circle).
Known larger populations in Germany existed up to the industrial-related heavy river water pollution in Saxony (e.g. in the Pulsnitz ), in Bavaria (e.g. in the Regen , the southern Regnitz and the Perlenbach ) and in North Rhine-Westphalia (e.g. B. in the Perlenbach in the Eifel ).
At the time of the small German states and princely courts up to the 18th century, it was partially deliberately settled and effectively protected against wild trapping with draconian punishments (e.g. chopping off the hand), as can be proven in the Odenwald and the Eifel. The right to search for pearls was known as the pearl regal . From 300 years ago, pearl mussel beds are known to have more than a thousand animals per square meter. With the invasion of the French in 1794, the pearl shelf became extinct in large parts of Germany, which enabled overexploitation .
The most important occurrence in the Czech Republic is the upper reaches of the Jankovský potok .
Only a few mussels actually contain pearls: the figures range from 0.05% to 4% (one pearl for every 2,000 or 25 mussels).
Today's occurrence in Germany
The pearl mussel is very rare in Germany today. The reasons for the decline in stocks are:
- Pollution of waters through over-fertilization, sewage discharge and road salt
- Silting up the streams
- Displacement of the brown trout , which serves as the host animal of the mussel, by the imported rainbow trout
- Extinction of the salmon , which serves as a host animal
- Destruction of entire stocks by pearl robbers in earlier times
- new predators by the neozoa muskrat and raccoon
In Germany the pearl mussel is classified as a national type of responsibility within the national strategy for biological diversity of the federal government. There are still deposits in Bavaria , North Rhine-Westphalia , Saxony , Rhineland-Palatinate and the Lüneburg Heath .
In Bavaria, the mussel was originally concentrated in three areas, of which the Bavarian Forest and Upper Franconia are still important today. There are only small residual deposits in the Upper Palatinate . In the Bavarian Forest, the area of the left tributaries of the Danube between Regensburg and Passau should be mentioned, the catchment areas of the rain and the Ilz in the former prince-bishopric of Passau have delivered particularly rich yields. The last occurrence on red sandstone in the Schondra (Bavaria) is a specialty .
The occurrence in the Vogelsberg and the Rhön in Hesse , which was documented until 2008, appears to have been extinct, the species is officially lost in the region, and it may have become extinct there.
In the Lutter - a river in the Lüneburg Heath - the major nature conservation project “Lutter” was successful in preserving the pearl mussel. The stock here, as the only one in Europe, has shown a positive development. For the first time in 1985, brown trout caught in the Lutter were infected with freshwater pearl mussel larvae and returned to the stream. However, these first measures were initially unsuccessful. The cause was the unnaturally high sand load of the Lutter, which was only discovered later. The scientific justification by Buddensiek (1991) and the confirmation in practice by Abendroth (1993) brought about the breakthrough. In 2008 more than 12,000 mussels were detected again.
In Rhineland-Palatinate, there are endangered stocks in the Our ( Eifel , 100 to 200 animals) and the Nister ( Westerwald , 26 known specimens). The stock in the nest has been rediscovered. The animals are 60 years and older. Natural reproduction has therefore not been proven for 60 years. Efforts are being made at both Our and Nister to support reproduction by bringing together glochidia and host fish in tanks.
Worldwide threat
According to the classification of the IUCN , the species is endangered worldwide (status: 1996), although the actual situation is insufficiently known. Due to its distribution only in densely populated Europe, in addition to water pollution and the factors listed above, due to the preference for lime-free streams with a high demand for lime for the shell, it is also threatened by acidification from acidic industrial and car exhaust gases even in otherwise clean and natural waters .
Legal protection status
According to the Federal Species Protection Ordinance, the freshwater pearl mussel is a strictly protected species under the Federal Nature Conservation Act.
It is also a species in Appendix II and Appendix V of the Habitats Directive .
Saprobic index
The saprobic index for this species is 1.0.
Individual evidence
- ↑ W.-D. Bischoff, W. Utermark: The river pearl mussel in the Lüneburg Heath, an attempt to preserve it… In: Nieders.Ministerium f. Nutrition, agriculture, etc. F. (Ed.): 30 years of nature conservation and landscape conservation. in Lower . 1976, p. 190-204 .
- ↑ S. Carl: The river pearl mussel (Margaritana margaritifera L.) and its pearls, with special consideration of the pearl mussel of the Odenwald and its history. In: Negotiations of the Natural Science Association in Karlsruhe 22, 1908/09, pp. 123–220.
- ↑ Manfred Braun, Gabriele Kurz: A rare inhabitant of the rivers . In: Rheinzeitung , weekend supplement : Journal Natur und Umwelt . February 14, 2009, p. 3 .
- ↑ Species in Germany's special responsibility. (No longer available online.) Federal Agency for Nature Conservation, archived from the original on August 2, 2017 ; accessed on August 16, 2017 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ Mark Harthun: Species extinction on the doorstep - The last river pearl mussel in Hesse. NABU Hessen, May 19, 2008, accessed September 4, 2008 .
- ↑ Reinhard Altmüller and Rainer Dettmer: Successful species protection measures for the freshwater pearl mussel Margaritifera margaritifera L. by reducing unnatural fine sediment loads in flowing waters - experiences within the framework of the Lutter project. In: Information service for nature conservation in Lower Saxony. Lower Saxony State Agency for Water Management, Coastal Protection and Nature Conservation, April 2006, accessed on August 16, 2017 .
- ↑ Shell returns. ( Memento of December 8, 2008 in the Internet Archive ) n-tv, December 4, 2007
- ^ V. Buddensiek: Investigation of the growth conditions of the freshwater pearl mussel ... in their early post-parasitic phase . Univ. Hanover, 1991 (Diss. FB. Biol.).
- ↑ D. Abendroth: Establishment and securing of parts of nature and landscape worthy of protection with state-wide represent. Meaning. In: Project Lutter: The Lutter - a heather flowing water in the Ldkrs. Celle u. Gifhorn (= Lower. - Nature and Landscape . No. 66 (1) ). 1993, p. 24-28 .
- ↑ Rediscovered: the pearl mussel. September 11, 2007, archived from the original on September 17, 2012 ; Retrieved February 15, 2009 .
- ↑ Breeding station for river pearl mussels on the Our - Luxembourg biologists want to save endangered species. September 16, 2011, archived from the original on February 12, 2013 ; Retrieved November 17, 2012 .
- ↑ Margaritifera margaritifera in the endangered Red List species the IUCN 1996. Retrieved on 16 August 2017th
- ↑ Meyer, Detlef .: Macroscopic biological field methods for assessing the water quality of rivers: with lists of species for beginning and experienced investigators and detailed descriptions and images of the indicator organisms . 4th, unchanged. BUND, Hannover 1990, ISBN 3-9800871-4-X .
literature
- Gerhard Bauer (Hrsg.): The river pearl mussel in Europe: Stock situation and protective measures. Results of the congress from 16. – 18. October 2000 in Hof . 2nd edition of the Wasserwirtschaftsamt , Hof 2002. Contribution partly in German, partly in English
- Otto Baer: The pearl mussel: Margaritifera margaritifera (L.); Ecology , environmental reactions and protection problems of an endangered species . 1st edition Westarp-Wiss., Magdeburg 1995. 118 pp. ISBN 3-89432-428-7
- Otto Moog (Hrsg.): Basics for the protection of the river pearl mussel in Austria . Zurich [et al.], 1993. Bristol series 3, ISBN 3-905209-02-0
- Bruno Rudau: The pearl mussel in the Vogtland past and present . Plauen, 1961. Museum series Vogtland District Museum No. 23
- Johann Gottlieb Jahn : The pearl fishing in Voigtlande in topographical, natural and contemporary history , Oelsnitz 1854. Digitized
Web links
- Elisabeth Strack: The European pearl mussel
- Jürgen Geist: Conservation Genetics and Ecology of European Freshwater Pearl Mussels (Margaritifera margaritifera L.) (Dissertation) (PDF file; 3.99 MB)
- SWR television report: Luxembourg biologists want to save endangered species
- LIFE funding project river pearl mussel