Calico cancer
| Calico cancer | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Orconectes immunis male (form I) |
||||||||||||
| Systematics | ||||||||||||
|
||||||||||||
| Scientific name | ||||||||||||
| Orconectes immunis | ||||||||||||
| ( Hagen , 1870) |
The orconectes immunis ( Faxonius immunis , originally Orconectes immunis ) is from North America originating crayfish . Outside of its original range, it now appears as a neozoon, probably as a result of aquarium exposures, also in the Baden-Württemberg Rhine plain and in Rhineland-Palatinate and is spreading very quickly. In doing so, it often reaches very high population densities and displaces the crayfish from its preferred habitats . Through movement and migration over land, the cancer has already penetrated ponds and lakes that are not directly connected to the waters of the Rhine system.
description
The calico cancer has some similarities with the crayfish . Both species are about the same size, calico crabs usually reach about nine centimeters in length, very rarely a little more. However, calico crayfish is dominant compared to crayfish of the same size. Tufts of hair on the inside of the scissor joint of the large scissors and on the first pair of legs are characteristic of calico crabs. The movable scissor finger carries a spike with a notch. He has a pair of eye strips. The dorsal furrows on the carapace converge closely, but do not touch. At least one thorn sits behind the neck furrows. The color is mostly beige-brown, rarely blue or pink. The underside is lighter than the back. Marble stains occur. As with the crayfish, the tips of the scissors are colored orange-red, but the calico crayfish lacks the dark band behind this drawing.
habitat
The calico crab originally inhabited the waters in the Mississippi catchment area from Montana to the confluence with the Gulf of Mexico . It was introduced to the northeastern states of the USA and Germany ; here it was first discovered in 1993 in the Sinzheim Schiftung; apparently someone had abandoned his aquarium animals. At times it occurred about 100 kilometers between Mannheim and Achern in the Rhine ; it is now more widespread. It also lives in oxbow lakes of the Rhine, in neighboring canals and in quarry ponds.
Life cycle
In contrast to the European crayfish, the calico crayfish is a pronounced r-strategist , with a high number of offspring (up to 500 per female) and has an extremely fast life cycle by Central European standards . After mating, the eggs are laid in late autumn and the young hatch from April, sometimes as early as March of the following year. After three to four months, the young can become sexually mature themselves . Life expectancy for crayfish is a relatively short three years.
food
The animals' diet consists mainly of insects such as dragonflies and frog spawn or tadpoles .
Others
Since 2017, biologists at the PH Karlsruhe (including Andreas Stephan, Alexander Herrmann and Prof. Andreas Martens) have been researching whether and how one could reduce the numbers of calico cancer again. The measures were described as successful in 2020.
See also
Web links
- Species description - in forum-flusskrebse.com ( Memento from January 19, 2010 in the Internet Archive )
- Orconectes immunis inthe IUCN 2013 Red List of Threatened Species . Posted by: Adams, S., Schuster, GA & Taylor, CA, 2010. Retrieved January 19, 2014.
- Identification key : edelkrebsprojektnrw.de (PDF)
Footnotes
- ↑ Jürgen Orr (2014): The calico crab Orconectes immunis (Hagen, 1870) - a still little noticed neozoon (AIS) with a significant risk potential for the aquatic communities of the Rheinaue (Crustacea, Decapoda, Cambaridae). Fauna and Flora in Rhineland-Palatinate, Vol. 12, Issue 4: 1403-1416.
- ↑ Chucholl, C. & Dehus, P. (2011): Crayfish in Baden-Württemberg . Fisheries Research Center Baden-Württemberg (FFS), Langenargen, 92 pages
- ↑ a b Heike Schwitalla: Danger to the local wildlife: American killer crab continues to spread on the Rhine , on: ka-news.de from June 1, 2018
- ↑ C. Chucholl (2012): Understanding invasion success: life-history traits and feeding habits of the alien crayfish Orconectes immunis (Decapoda, Astacida, Cambaridae) in Knowl. Managed. Aquatic Ecosyst. Number 404, 2012. 22 pages.
- ↑ Badische Zeitung: Why is calico cancer dangerous? - Explain it to me - Badische Zeitung . ( badische-zeitung.de [accessed on July 24, 2018]).
- ↑ Nadja Prodbregar: Successful fight against calico cancer , on: Wissenschaft.de from July 31, 2020