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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Krill is a shrimp-like marine invertebrate animal. These small crustaceans are important organisms of the zooplankton, particularly as food for baleen whales, manta rays, whale sharks, crabeater seals, other seals, and a few seabird species that feed almost exclusively on them. Krill occur in all oceans of the world. They are considered an important trophic connection – near the bottom of the food chain – because they feed on phytoplankton and to a lesser extent zooplankton, converting these into a form suitable for many larger animals for whom krill makes up the largest part of their diet. In the Southern Ocean, one species, the Antarctic krill, Euphausia superba, makes up an estimated biomass of over 500 million tonnes, roughly twice that of humans. Of this, over half is eaten by whales, seals, penguins, squid and fish each year, and is replaced by growth and reproduction. Most krill species display large daily vertical migrations, thus providing food for predators near the surface at night and in deeper waters during the day.

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Did you know?

... that the freshwater crab Guinotia dentata (pictured) prefers shady rivers to sunny ones?
... that a young spider crab, Libinia ferreirae, often lives inside the bell of the jellyfish Lychnorhiza lucerna?
... that Trachysalambria curvirostris, one of the most important species of fished prawns, is abundant around Australia but is considered too small to be commercial there?
... that despite writing many scientific papers at Yale University and having the time limit waived, the carcinologist Martin Burkenroad never submitted a dissertation?

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Edward J. Miers F.Z.S. F.L.S. (1851–1930) was a British zoologist and curator of the crustacean collection at the Natural History Museum in London. He contributed to the scientific reports from the Challenger expedition of 1872–1876, and described 32 new genera and at least 260 new species and subspecies of decapod crustaceans, along with four genera and 72 new species in other orders.

Miers published his Catalogue of the stalk- and sessile-eyed Crustacea of New Zealand in 1876 and revised the Plagusiinae, Hippidae, Majidae, Squillidae and Idoteidae in monographs dated 1878–1881. He also reported on the collections donated by the Admiralty from a number of voyages, including the survey of the coast of Japan by H.M.S. Sylvia (1870–1877), an expedition to view the Transit of Venus in Kerguelen and Rodrigues (1874–1875), a survey of the Galápagos Islands by H.M.S. Petrel, Novaya Zemlya by H.M.S. Isbjorn (1879), Baron Hermann-Maltzan's voyage to Gorée in 1881, and the voyages of H.M.S. Alert to Patagonia and the Strait of Magellan (1881–1882). The upheavals at his workplace and the quantity of work to be done may have taken their toll on Miers, and he was "completely prostrated with illness" for three months.

Miers was still working on material from the Alert expedition, when six boxes containing the crabs from the Challenger expedition arrived, sent by John Murray. Describing these crabs would be Miers' largest taxonomic work, one which was published in 1886 as Report on the Brachyura collected by H. M. S. Challenger during the years 1873–1876 in 1886. Miers' honorarium for this work was £63 (60 guineas).

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Credit: George Chernilevsky

Hermit crabs, such as Clibanarius erythropus, inhabit discarded gastropod shells in order to protect their soft and vulnerable abdomen.

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General images

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

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