Portal:Crustaceans

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The Crustaceans Portal

Crustaceans are a 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 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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Carcinus maenas, the shore crab or green crab, is a common littoral crab, and an important invasive species, listed among the 100 "world's worst alien invasive species". Although native to the Baltic Sea, North Sea and north-east Atlantic Ocean, it has since become established on both east and west coasts of North America, in Argentina, South Africa and Australia. C. maenas is a predator feeding on many organisms, particularly bivalve molluscs (such as clams, oysters, and mussels), polychaetes and small crustaceans. It is primarily nocturnal, although activity also depends on the tide, and crabs can be active at any time of day.

Did you know?

Scyllarides latus (Decapoda: Scyllaridae) by Cornelius Sittardus

... that all that remains of the type specimen of the Mediterranean slipper lobster is a 16th century watercolour (pictured)?
... that the blind crustacean Polycheles typhlops preys on fish and on other crustaceans, probably acting as an ambush predator?
... that Edward J. Miers was paid 60 guineas for his monograph on the crabs of the Challenger expedition?
... that the genus Platythelphusa represents the only evolutionary radiation of crabs to have occurred in a freshwater lake?

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

Nebalia bipes is a species of leptostracan crustacean, and, in 1780, the first species in the order to have been described.

General images

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

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