The Crustaceans Portal

Abludomelita obtusata, an amphipod
Abludomelita obtusata, an amphipod

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 (/krəˈstʃə/), 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...)

Selected article

Dyspanopeus sayi (Decapoda: Brachyura: Panopeidae)
Dyspanopeus sayi is a species of mud crab that is native to the Atlantic coast of North America. It has also become established outside its native range, living in Swansea Docks since 1960, the Mediterranean Sea since the 1970s, the North Sea since 2007 and the Black Sea since 2010. It can reach a carapace width of 20 mm (0.8 in), and has black tips to its unequal claws. It feeds on bivalves and barnacles, and is in turn eaten by predators including the Atlantic blue crab, Callinectes sapidus. Eggs are produced from spring to autumn, the offspring reach sexual maturity the following summer, and individuals can live for up to two years. The closest relative of D. sayi is D. texanus, which lives in the Gulf of Mexico; the two species differ in subtle features of the genitalia and the last pair of walking legs.

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Dardanus calidus (Decapoda: Diogenidae) and Calliactis parasitica (Cnidaria: Actiniaria)
Dardanus calidus (Decapoda: Diogenidae) and Calliactis parasitica (Cnidaria: Actiniaria)

Selected biography

William Elford Leach FRS (February 2, 1790 – August 26, 1836) was an English zoologist and marine biologist. In 1813, Leach was employed as assistant librarian in the Zoological Department at the British Museum. He set himself to sorting out the collections, many of which had been neglected since they had been left to the museum by Hans Sloane. During his time there he was made assistant keeper of the natural history department and became an expert on crustaceans and molluscs. In 1817, he was elected a fellow of the Royal Society. Leach also worked and published on insects, myriapods, arachnids, mammals and birds. Leach's nomenclature was a little eccentric - he named twenty-seven species after his friend John Cranch, who had collected the species in Africa and later died on HMS Congo. In 1818, he named nine genera after Caroline or anagrams of that name, possibly after his mistress. In 1821, he suffered a nervous breakdown due to overwork, and he resigned from the museum in March 1822. His elder sister took him to continental Europe to convalesce, and they travelled through France, Italy and Greece. He died of cholera in the Palazzo San Sebastiano, near Tortona, north of Genoa.

Selected image

Metacarcinus magister (Decapoda: Cancridae)
Metacarcinus magister (Decapoda: Cancridae)
Credit: Kevin Cole

The Dungeness crab, Metacarcinus magister (formerly Cancer magister), is a species of crab that inhabits East Pacific eelgrass beds and water bottoms from Alaska's Aleutian Islands to Santa Cruz, California.

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