Portal:Crustaceans

The Crustaceans Portal

Crustaceans (from Latin word "crustacea" meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are traditionally a part of the subphylum Crustacea (/krəˈsteɪʃə/), a large, diverse group of mainly aquatic arthropods including the more familiar decapods (shrimps, prawns, crabs, lobsters and crayfish), seed shrimps, 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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Chirocephalus diaphanus is a widely distributed European species of fairy shrimp that lives as far north as Great Britain, where it is the only surviving species of fairy shrimp and is protected under the Wildlife and Countryside Act 1981. It is a translucent animal, about 0.5 in (13 mm) long, with reddened tips to the abdomen and appendages. The body comprises a head, a thorax bearing 11 pairs of appendages, and a seven-segmented abdomen. In males, the antennae are enlarged to form "frontal appendages", while females have an egg pouch at the end of the thorax.

The life cycle of C. diaphanus is extremely fast, and the species can only persist in pools without predators. The eggs tolerate drying out, and hatch when re-immersed in water. C. diaphanus was first reported in the scientific literature in 1704, but was only separated from other species and given its scientific name in 1803; the specific epithet diaphanus refers to the animal's transparency.

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Did you know?

... that the pill bug Armadillidium vulgare (pictured) can reach population densities of 10,000 per square metre?
... that the extinct crab Metacarcinus starri from Washington state is related to the graceful rock crab?
... that the extinct prawn Aciculopoda, described in 2010, is the third unambiguous fossil decapod from before the Mesozoic?
... that Mary J. Rathbun described over 1000 new crustacean taxa, but never attended college, and received a Ph.D. only after she retired?

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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.

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Credit: Nick Hobgood

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.

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General images

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

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