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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The Japanese spider crab (Macrocheira kaempferi) is a species of marine crab and is the biggest one that lives in the waters around Japan. It has the largest known leg-span of any arthropod around 3.7 meters. The Japanese name for this species is taka-ashi-gani, (Japanese: たかあしがに), literally translating to “tall legs crab”. It goes through three main larval stages along with a prezoeal stage to grow to its great size.

The genus Macrocheira contains multiple species. Two fossil species of this genus have been found, M. ginzanensis and M. yabei, both from the Miocene of Japan. Its diverse taxonomic history is an important part of what these creatures are and how they evolved to be what they are today. They are sought by crab fisheries, and are considered a delicacy in Japan. To prevent overexploitation from harming the species, conservation efforts have been put in place to protect these creatures and their population from overfishing. (Full article...)

Did you know?

... that although the Pacific sand crab can only crawl and burrow backwards (pictured), it can also tread water?
... that Praunus flexuosus, the first mysid shrimp ever to be described, may have been transported to North America during World War II?
... that Calcinus tubularis is one of only two known species of hermit crab whose males and females inhabit different types of shell?
... that Petrolisthes eriomerus, when trying to escape from a predator, can cast off limbs as a diversion, with the claws of a cast limb still gripping vigorously after separation?

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Robert Gurney (July 31, 1879 – March 5, 1950) was a British zoologist most famous for his monographs on British Freshwater Copepoda (1931–1933) and the Larvae of Decapod Crustacea (1942). He was born in 1879 as the fourth son of John Gurney and Isabel Charlotte Gurney (later Baroness Talbot de Malahide) of Sprowston Hall, Norfolk. He went to school at Eton College, and went on to study at New College, Oxford, graduating with first class honours in 1902. He was never associated with any institution, but worked from his home, initially in Norfolk, but later at Boars Hill. Realising the need for a specialist field station for freshwater biology to match the marine biological stations at Plymouth and Naples, Robert and his brother Eustace set up Great Britain's first freshwater laboratory at Sutton Broad. Gurney's two great study objects were the Copepoda and the larvae of Decapoda (zoea larva of Homarus gammarus pictured), and his greatest works were the three-volume monograph British Freshwater Copepoda, published by the Ray Society in 1931–1933, and his Larvae of Decapod Crustacea published by the Ray Society in 1942. Gurney travelled to North Africa and Bermuda, and received material from other foreign expeditions, including the Terra Nova Expedition (1910–1913) and the Discovery Investigations of the 1920s and 1930s.

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Credit: Hans Hillewaert

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

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

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