Decapoda
The decapods ( Decapoda ) make an order within the class of Higher cancers. Approximately 10,000 species of crustaceans are among the decapods, including the well-known groups such as the United cancers to which the crayfish and lobsters are the hermit crabs, crabs, lobsters and most shrimp. Thus, they are after the ostracods, copepods and isopods the most species-rich cancer group.
Features
Decapods are between one millimeter ( a type of partner shrimp ) and 60 centimeters ( the spiny lobster Jasus hilly ) long and in places with the Japanese giant crab and crustacean with the largest span of the limbs (3.7 m). They have produced a wealth of body shapes. Always it is however divided into cephalothorax and abdomen. The shrimp, lobster and crayfish -like decapods have an elongated, laterally often slightly flattened body, the cephalothorax runs forward in an often serrate rostrum. Their antennae are long. The first two to three walking legs bear claws. The abdomen is clearly divided, provided with swimming legs, ending in a tail fan, with which they can escape backwards quickly in case of danger. The Crabs of the body, however, is more broad than long. A rostrum and a tail fan missing, so that the animals also can not swim backwards. The antennae are short, the abdomen is short, narrow and worn folded under the cephalothorax forward. Since the swimming legs are atrophied, or be used in females only when moving the eggs, most crabs can not swim. The crabs, however, have recovered their swimming ability again by their hind legs were converted into paddle-like organs. A third body type is represented by the hermit crabs that are unbalanced, to hide in snail shells and their abdomen is soft and swollen, as it contains some organs that sit in other decapods in the cephalothorax.
Dissemination
Decapods are mainly marine life and in all oceans at home, in the polar but only few species. Particularly rich in species, they occur on the coasts, from the shelf to the intertidal zone. They live mainly on the sea floor, pelagic open water species are rare. Different groups have migrated in fresh waters or to land-dwelling passed (eg the coconut crab ). However, all decapods have to go back or to the water to breed. Finds of fossil crabs of this order are common in the Ziegeleitongrube of Engelbostel.
System
Within the Decapoda two monophyletic suborders are distinguished which Dendrobranchiata and Pleocyemata. A more detailed description of the system is in the classification of decapods.
- Order decapods ( Decapoda ) Subordination Dendrobranchiata
- Subordination Pleocyemata Infraorder Achelata
- Infraorder means crabs ( Anomura )
- Infraorder Astacidea ( Astacidea )
- Infraorder Axiidea
- Infraorder crabs ( Brachyura )
- Infraorder Caridea
- Infraorder Gebiidea
- Infraorder Glypheidea
- Infraorder Polychelida
- Infraorder Stenopodidea
Use
Decapods are considered a delicacy and are an important fishery product. Especially in the cold water of the deep sea live shrimp species are fished, living in the warm water species in India, Southeast Asia, the USA and South America bred in aquaculture. Is mainly eaten the flesh of the abdomen, which contains only muscle and no organs in lobster and crab also the flesh of scissors.