Noble cancer
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Noble crayfish ( Astacus astacus ) |
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| ( Linnaeus , 1758) |
The European crayfish or European crayfish ( Astacus astacus ) is the largest of the cancers native to Europe . He will be 15 to 20 years old. The scientific species name is derived from the ancient Greek word astakos , "cancer".
description
The noble crab can grow up to 20 cm (from head to tail) and weigh up to 350 g. There are two pairs of antennae on the head, one of which is about 1/3 the length of the body. The second pair is very short and can only be seen up close. There are two pairs of horn-like structures (postorbital ridges) around the eyes that protect the eyes. The crayfish has two claws that are used to hold prey and for defense. The body is usually dark brown to reddish brown, but blue animals also occur. The head and back armor is pointed. Undersides and joints of the scissors are red (an important distinguishing feature from other species of crayfish).
Gender recognition
In the male, the last two pairs of webbed feet are transformed into mating organs (gonopods). These feet of the foremost two abdominal segments are carried folded forward so that they completely hide the (small) genital opening (between the last and penultimate pair of legs on the underside of the thorax). The abdomen is narrower than the thorax at the base. In a direct comparison between males and females, the male has a significantly narrower abdomen. This difference can be seen particularly clearly from above.
The female is best recognized when it bears eggs on the underside of the abdomen (ventral), otherwise by the fallopian tube openings (gonopores) at the base of the third pair of striding legs. In the female, the genital opening (between the last and penultimate pairs of legs on the underside of the thorax) is relatively small and is exposed. The sexual opening of the male on the 5th strider leg is clearly visible as a white, soft hill. All webbed feet are carried backwards. The abdomen has almost the same width as the thorax at the base. The males have wider and larger claws. Females are significantly smaller. They reach sexual maturity at the age of three.
Multiplication
pairing
Mating occurs when the water temperature drops in autumn . The males hold the females with scissors and turn them on their backs or on their side. The females are cooperative when they are ready to mate, so that much smaller males are also able to mate physically superior females. During this mating, the males attach with their fertilization bones (gonopods), small white, about 1 mm thick rod-shaped seed packets with a covering ( spermatophores ) to the females. These are usually found on the underside of the abdomen (ventral), between the last striding legs or on the tail fan.
The eggs, 50 to 400 pieces, are carried by the female for 26 weeks under the battered abdomen.
Larvae and crabs
The almost fully developed crab larvae hatch between May and June and have a yolk sac during the first few days . The little crabs are almost transparent and shed their skin for the first time after about ten days. The young crabs stay with the mother for a few days. However, a maximum of 10 to 20% of the eggs develop into young cancer.
In the first year there are 7 to 10 moults, in the second year 4 to 5 moults. In the third year there are still 2 to 3 moults.
habitat
The noble crayfish loves warm, nutrient-rich waters in the lowlands , but it can also be found in flowing waters at higher elevations. Summer temperatures must reach 16 ° C for 2 to 3 months, otherwise there will be no development of the genitals (gonads) and thus no reproduction. The crab avoids very muddy waters because it likes to dig caves. These are the bank embankments created or under rocks, roots and dead wood . It is sensitive to chemical pollution, especially insecticides . It does not hibernate, but only rests for a few weeks.
distribution
Historically the noble crayfish occurs in almost all of Europe . It is only missing on the Iberian Peninsula , Northern England and Ireland .
Danger
The noble crayfish is generally pushed back considerably by the nature-remote construction of the water and the pollution of the water. The greatest threat, however, is the cancer plague . The cancer plague was introduced by the colonization of American crayfish species (e.g. signal crayfish or crayfish ). These cancers are hosts for the pathogen, but in contrast to noble cancer, they only die from it in exceptional cases. The competitive superiority of these new species has further exacerbated the situation and decimated the noble crayfish so extremely in almost all European countries that it can only be found in a few island biotopes in Central Europe.
The endangerment situation is shown in some Red Lists of endangered animal species. The World Conservation Organization IUCN puts the entire inventory in the 2009 edition of the Red List in the "Vulnerable" category. In Germany, the noble crayfish is classified as critically endangered (cat. 1) on the national red list. Switzerland indicates it as endangered (cat. 3). The noble crab has been named " Fish of the Year " 2019 in Austria .
Protective measures
In the Bern Convention , the noble crayfish was declared a protected species with a use adapted to the hazard situation. By adopting this provision in the Fauna-Flora-Habitat Directive No. 92/43 / EEC or the new version No. 2006/105 / EC, Appendix V of the European Union, its further use in the German Federal Nature Conservation Act , where the species is considered strict protected, and the listing in the Federal Species Protection Ordinance enables special protective measures with regard to use. For example, the catch of wild crayfish is not permitted in Germany without official approval.
Resettlement projects are occasionally reported.
The Switzerland , this type of cancer in Annex 1 of the Ordinance to the Federal Law on Fisheries ( "VBGF") in the hazard category 3 and called them so as endangered. This categorization enables protective measures that are adapted to the situation and appropriate to it.
See also
Web links
- Online identification key for crayfish in Baden-Württemberg
- Endangerment of the native crayfish by alien crayfish species
- Raising of noble crayfish in farms
- Astacus astacus in the endangered Red List species the IUCN 2009. Posted by: Sket, 1996. Retrieved on January 3 of 2010.
- Capture, protection, advice
- Crayfish in Saxony , recording the population of crayfish in the Free State of Saxony (PDF file, 12.33 MB)
Individual evidence
- ↑ Chucholl, C. & Dehus, P. (2011): Crayfish in Baden-Württemberg . Fisheries Research Center Baden-Württemberg (FFS), Langenargen, 92 pages
- ↑ Chucholl, C. & Blank, S. & Brinker, A. (2017): The protection of the crayfish - A guide . Ministry for Rural Areas and Consumer Protection Baden-Württemberg, Stuttgart, 84 pages
- ↑ math.hu-berlin.de/~teschke/krebs.htm - The Jasmund National Park - noble crabs on Rügen in Lake Herthasee
- ^ Dietrich Blanke: Crayfish in Lower Saxony In: Informationsdienst Naturschutz Niedersachsen, 1998, Issue 6, 146-174
- ↑ Development of a molecular biological method for the detection of the crustacean pathogen Aphanomyces astaci SCHIKORA in North American crayfish (Pacifastacus leniusculus; Orconectes limosus; Procambarus clarkii) (PDF; 9.9 MB)
- ↑ Appendix 1 Native species of fish and crabs in Switzerland. In: The Federal Authorities of the Swiss Confederation. Retrieved January 25, 2010 .
European grayling (2002) | Nose (2003) | Aland (2004) | Arctic char (2005) | Koppe (2006) | Tench (2007) | Bitterling (2008) | Eel (2009) | Crucian carp (2010) | European grayling (2011) | Huchen (2012) | Lake trout (2013) | Sterlet (2014) | Nose (2015) | Minnow (2016) | Arctic char (2017) | European catfish (2018) | Noble Cancer (2019)