Cherax destructor
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| Clark , 1936 |
Cherax destructor is a species of decapod fromthe Parastacidae family . This crab, up to 28 centimeters long, isnativeto Australia and lives in freshwater . It is a popular table and aquarium crayfish.
features
The rostrum of Cherax destructor is twice as long as it is wide at its base and extends to the third segment of the first antennae. The rostrum has a sting on each side. The carapace is shorter than the abdomen , slightly wider than it is tall and twice as long as it is wide. The postcervical groove running across the carapace is very clear. The carapace is finely dotted. The telson has a small spike on each side. The large scissors on the first pair of striding legs are long and strong. Its upper edge has many tubercles , the lower edge is smooth. The inner edges of the scissor fingers are only slightly toothed. The size and shape of the scissors appear to vary between individuals of this species.
The color of Cherax destructor can vary considerably, but is mostly olive-green to brown. However, black, blue or red animals have already been found. They reach body lengths of over 28 centimeters.
distribution
Cherax destructor is common in Australia, the states of Victoria , New South Wales , southern Queensland , South Australia, and parts of the Northern Territory . There it can be found in a number of habitats, for example in swamps, streams or rivers. They can also be found in ponds. If their habitat dries up, they dig up to the damp ground and remain until water is available again. They tend to live on muddy grounds with moderate cloudiness than in clear water, as this offers more protection against predation . The optimal water temperature is between 20 and 25 ° C, temperatures up to 1 ° C or 35 ° C can be tolerated for a short time. They tolerate a wide range of salinity and oxygen levels.
In the IUCN Red List , Cherax destructor is classified as endangered (vulnerable) in its natural range. The reasons for the endangerment include the pollution of the water and the competitive pressure from neozoa .
Reproduction
Reproduction at Cherax seems to be destructor dependent on water temperature and day length. When the water temperature rises above 15 ° C in spring or early summer, mating takes place. The females spawn between October and January, fertilized eggs are attached to the swimming legs . The eggs are olive-green in color and about 2 millimeters long and rather oval. Young females produce 100 to 300 eggs, older more than 1000. Incubation takes between 19 and 40 days, depending on the water temperature. After the larvae hatch, they stay with the mother for a few weeks and go through some larval stages. As soon as the young animals leave the female, it can spawn again if the environmental conditions permit.
Juvenile Cherax destructor can reach sexual maturity after 12 months if they are optimally grown. After two to three years, they are about 10 centimeters long and 320 grams.
nutrition
Cherax destructor is rather nocturnal and remains in its hiding place during the day. Foraging is usually done shortly before sunrise and shortly after sunset. They are opportunistic omnivores but mainly feed on detritus . The exuvia , the old exoskeleton stripped off after a molt, is also eaten. Cannibalism can occur.
While many crabs (like most animals) break down cellulose with the help of the cellulases of their endosymbionts , Cherax destructor has its own ( endogenous ) cellulase and is therefore not dependent on endosymbionts to generate energy from cellulose.
Economic importance
The species is bred commercially in Australia, the main producers are South Australia (about 14 t in 1989/1990) and Western Australia (about 40 t in 1989/1990, summarized with Cherax plebejus ). Although there are also large, specialized breeding farms, the use of artificial water basins (drinking troughs for sheep breeding) is predominant. The species has also been exported to other countries for aquaculture. In Europe there are breeding farms in Italy (Piedmont). The transport of these and some other species within Australia is also viewed critically as a possible threat to endemic crayfish species. In Italy and other countries, too, it is feared that it will be introduced as a neozoon . Cherax destructor , like all Australian Parastacids, is sensitive to cancer plague . This and its high temperature requirements probably prevent settlement in Central Europe.
literature
- Ellen Clark: The freshwater and land crayfishes of Australia . In: Memoirs of Museum Victoria . tape 10 , 1936, pp. 5-58 ( Biodiversity Heritage Library-Australia (BHL) [accessed January 23, 2013]).
Individual evidence
- ↑ Ellen Clark, 1936; s. literature
- ↑ a b c d e f g Fiona Withnall: Biology of Yabbies (Cherax destructor) . Ed .: State of Victoria, Department of Natural Resources and Environment. 2000 ( PDF, 79kB [accessed on January 23, 2013]). PDF, 79kB ( Memento of the original from June 20, 2005 in the Internet Archive ) 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.
- ↑ a b c d Yabbie. Government of South Australia - Department of Primary Industries and Regions SA (PIRSA), January 18, 2013, accessed January 23, 2013 .
- ↑ Cherax destructor in the Red List of Threatened Species of the IUCN 2012. Posted by: Crandall, KA, 1996. Accessed July 26, 2012 found.
- ↑ Yabbie crayfish (Cherax destructor). (No longer available online.) Arkive.org - Wildscreen, archived from the original on February 4, 2013 ; Retrieved January 23, 2013 . 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.
- ↑ Allardyce, Benjamin J., Stuart M. Linton: and characterization of endo-β-1, 4-glucanase and laminarinase enzymes from the gecarcinid land crab Gecarcoidea natalis and the aquatic crayfish Cherax destructor. Journal of Experimental Biology, Vol. 211, No. 14, 2008, pp. 2275-2287.
- ↑ David M. Holdich (1993): A review of astaciculture: freshwater crayfish farming. Aquatic Living Resources 6: 307-317.
- ↑ P. Horwitz (1990): The translocation of freshwater crayfish in Australia: Potential impact, the need for control and global relevance. Biological Conservation 54: 291-305.
- ↑ Massimiliano Scalici, Stefania Chiesa, Francesca Gherardi, Marina Ruffini, Giancarlo Gibertini, Francesco Nonnis Marzano (2009): The new threat to Italian inland waters from the alien crayfish “gang”: the Australian Cherax destructor Clark, 1936. Hydrobiologia Volume 632, Issue 1: 341 - 345.
