Crustacean

Crustaceans are a large, diverse group of arthropods, including familiar animals such as crabs, lobsters, crayfish, shrimp, krill, and barnacles. The crustacean group can be treated as a subphylum under the phylum Arthropoda, and is usually divided into classes.

Characteristics

Crustaceans are generally aquatic and differ from other arthropods in their body structure and function. They have two pairs of antennae, a pair of mandibles, and two pairs of maxillae on their heads. They also have a hard exoskeleton that protects their bodies.

Classification

Crustaceans are typically classified into the following classes:

• Class Malacostraca: This includes crabs, lobsters, crayfish, shrimp, krill, woodlice, and others.
• Class Branchiopoda: This includes brine shrimp and Daphnia.
• Class Cephalocarida: This includes horseshoe shrimp.
• Class Maxillopoda: This includes barnacles, copepods, and a number of related animals.
• Class Ostracoda: This includes seed shrimp.

Ecology and Life Cycle

Crustaceans play key roles in marine and freshwater ecosystems, where they serve as the primary consumers of algae and detritus, and as prey for numerous larger animals. The life cycle of crustaceans varies greatly, but most species hatch from eggs as a larva that undergoes several stages of development before reaching adulthood.

Economic Importance

Many crustaceans are vital to human economies and are among the most widely consumed types of seafood worldwide. They are also used in research and are important indicators of ecosystem health.

See Also

• Arthropod
• Marine biology
• Aquaculture

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  Sally Lightfoot crab
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  European lobster
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  Red swamp crayfish
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  Cleaner shrimp
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  Antarctic krill
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  Desert isopod
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  Copepod
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  Poli's stellate barnacle
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  Crab from Long Island
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  Krill anatomy
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  Abludomelita obtusata
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  Freshwater crab