Search results
Results From The WOW.Com Content Network
Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are a part of the subphylum Crustacea (/ k r ə ˈ s t eɪ ʃ ə /), a large, diverse group of mainly aquatic arthropods including decapods (shrimps, prawns, crabs, lobsters and crayfish), seed shrimp, branchiopods, fish lice, krill, remipedes, isopods ...
The leg of a squat lobster, showing the segments; the ischium and merus are fused in many decapods. The legs of crustaceans are divided primitively into seven segments, which do not follow the naming system used in the other groups. They are: coxa, basis, ischium, merus, carpus, propodus, and dactylus.
Pereiopods are primarily walking legs and are also used for gathering food. They are also the ten legs from which decapods take their name. [2] Those pereiopods which are armed with a claw may be referred to as chelipeds. The moveable fingers of a claw are known as dactyli. The pereiopods bear the sexual organs, which are the third pereiopod in ...
' ten-footed ') is a large order of crustaceans within the class Malacostraca, and includes crabs, lobsters, crayfish, shrimp, and prawns. Most decapods are scavengers. The order is estimated to contain nearly 15,000 extant species in around 2,700 genera, with around 3,300 fossil species. [1]
Shrimp is characteristically used to refer to those crustaceans with long antennae, slender legs, and a laterally compressed, muscular abdomen that is highly adapted for both forward swimming and a backward (retrograde) escape response. Prawn is often used as a synonym of shrimp for penaeoidean and caridean shrimp, especially those of large size.
These, like the maxillipeds of crustaceans, are modified legs and not true mouthparts. [2] The forcipules arise from the first body segment, curving forward and to the midline. The tip is a pointed fang, which has an opening from a venom gland. The forcipules are used to capture and envenomate prey.
The 67,000 described species range in size from Stygotantulus stocki at 0.1 mm (0.004 in), to the Japanese spider crab with a leg span of up to 3.8 m (12.5 ft) and a mass of 20 kg (44 lb). Like other arthropods, crustaceans have an exoskeleton, which they moult to grow.
Crabs vary in size from the pea crab, a few millimeters wide, to the Japanese spider crab, with a leg span up to 4 m (13 ft). [6] Several other groups of crustaceans with similar appearances – such as king crabs and porcelain crabs – are not true crabs, but have evolved features similar to true crabs through a process known as carcinisation .