Portal:Crustaceans

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The Crustaceans Portal

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 (/krəˈsteɪʃə/), a large, diverse group of mainly aquatic arthropods including decapods (shrimps, prawns, crabs, lobsters and crayfish), seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, opossum shrimps, amphipods and mantis shrimp. The crustacean group can be treated as a subphylum under the clade Mandibulata. It is now well accepted that the hexapods (insects and entognathans) emerged deep in the Crustacean group, with the completed pan-group referred to as Pancrustacea. The three classes Cephalocarida, Branchiopoda and Remipedia are more closely related to the hexapods than they are to any of the other crustaceans (oligostracans and multicrustaceans).

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. They are distinguished from other groups of arthropods, such as insects, myriapods and chelicerates, by the possession of biramous (two-parted) limbs, and by their larval forms, such as the nauplius stage of branchiopods and copepods.

Most crustaceans are free-living aquatic animals, but some are terrestrial (e.g. woodlice, sandhoppers), some are parasitic (e.g. Rhizocephala, fish lice, tongue worms) and some are sessile (e.g. barnacles). The group has an extensive fossil record, reaching back to the Cambrian. More than 7.9 million tons of crustaceans per year are harvested by fishery or farming for human consumption, consisting mostly of shrimp and prawns. Krill and copepods are not as widely fished, but may be the animals with the greatest biomass on the planet, and form a vital part of the food chain. The scientific study of crustaceans is known as carcinology (alternatively, malacostracology, crustaceology or crustalogy), and a scientist who works in carcinology is a carcinologist. (Full article...)

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Selected article

Potamon fluviatile is a freshwater crab found in or near wooded streams, rivers and lakes in Southern Europe. It is an omnivore with broad ecological tolerances, and adults typically reach 50 mm (2 in) in size during their 10–12 year lifespan. They inhabit burrows and are aggressive, apparently outcompeting native crayfish. P. fluviatile has been harvested for food since Classical antiquity, and is now threatened by overexploitation. Many of the island populations are particularly vulnerable, and the Maltese subspecies has become a conservation icon. A population in Rome is the only population of freshwater crabs to occur in the middle of a large city, and may have been brought there before the founding of the Roman Empire.

Did you know?

... that giant isopods (pictured), which live in the depths of the Atlantic and Pacific Ocean, can grow up to 45 centimetres long?
... that until 2001, the Ohio River shrimp had not been seen in the Ohio River for 50 years?
... that the semaphore crab is the most abundant crab species in mangroves on Australia's east coast?
... that Japan and Poland are the world's largest krill fishing nations since Russia abandoned its operations in 1993?

Selected biography

Charles Robert Darwin FRS (February 12, 1809 – April 19, 1882) was an English naturalist who established that all species of life have descended over time from common ancestors, and proposed the scientific theory that this branching pattern of evolution resulted from a process that he called natural selection. In 1846, Darwin returned to a fascination in marine invertebrates, dating back to his student days with Robert Edmond Grant, by dissecting and classifying the barnacles (Cirripedia) he had collected on his voyages. In the following eight years of work on barnacles, Darwin's theory of natural selection helped him to find homologies, showing that slightly changed body parts served different functions to meet new conditions, and in some genera he found minute males parasitic on hermaphrodites, showing an intermediate stage in the evolution of distinct sexes. In 1853, this work earnt Darwin the Royal Society's Royal Medal, and it made his reputation as a biologist. Even without publication of his works on evolution, Darwin would have had a considerable reputation as the author of The Voyage of the Beagle, as a geologist who had published extensively on South America and had solved the puzzle of the formation of coral atolls, and as a biologist who had published the definitive work on barnacles.

Selected image

Periclimenes imperator (Decapoda: Palaemonidae) is a species of shrimp with a wide distribution across the Indo-Pacific that lives commensally on a number of hosts, including the sea slug Hexabranchus.

General images

The following are images from various crustacean-related articles on Wikipedia.

Image 1Odontodactylus scyllarus (Hoplocarida: Stomatopoda) (from Malacostraca)
Image 2Body structure of a typical crustacean – krill (from Crustacean)
Image 3Copepods, from Ernst Haeckel's 1904 work Kunstformen der Natur (from Crustacean)
Image 4Cancer pagurus (Eucarida: Decapoda) (from Malacostraca)
Image 5A shed carapace of a lady crab, part of the hard exoskeleton
Image 6Anatomy of Cypridina mediterranea (from Ostracod)
Image 7Articulated ostracod valves in cross-section from the Permian of central Texas; typical thin section view of an ostracod fossil (from Ostracod)
Image 8Decapods, from Ernst Haeckel's 1904 work Kunstformen der Natur (from Crustacean)
Image 9Squilla empusa,
a mantis shrimp (from Malacostraca)
Image 10The large ostracod Herrmannina from the Silurian (Ludlow) Soeginina Beds (Paadla Formation) on eastern Saaremaa Island, Estonia (from Ostracod)
Image 11Eggs of Potamon fluviatile, a freshwater crab
Image 12Zoea larva of the European lobster, Homarus gammarus
Image 13Abludomelita obtusata, an amphipod (from Crustacean)
Image 14Ostracod (from Ostracod)
Image 15Grapsus grapsus, a terrestrial crab (from Malacostraca)
Image 16Artemia salina (Anostraca: Artemiidae) (from Branchiopoda)
Image 17Porcellio scaber and Oniscus asellus (Peracarida: Isopoda) (from Malacostraca)
Image 18Norway lobsters on sale at a Spanish market
Image 19Leptostraca such as Nebalia bipes retain the primitive condition of having seven abdominal segments. (from Malacostraca)
Image 20Daphnia pulex (Cladocera: Daphniidae) (from Branchiopoda)
Image 21Eryma mandelslohi, a fossil decapod from the Jurassic of Bissingen an der Teck, Germany
Image 22Ostracod swimming motions (in real time) (from Ostracod)