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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There is a scientific debate which questions whether crustaceans experience pain. It is a complex mental state, with a distinct perceptual quality but also associated with suffering, which is an emotional state. Because of this complexity, the presence of pain in an animal, or another human for that matter, cannot be determined unambiguously using observational methods, but the conclusion that animals experience pain is often inferred on the basis of likely presence of phenomenal consciousness which is deduced from comparative brain physiology as well as physical and behavioural reactions.

Definitions of pain vary, but most involve the ability of the nervous system to detect and reflexively react to harmful stimuli by avoiding it, and the ability to subjectively experience suffering. Suffering cannot be directly measured in other animals. Responses to putatively painful stimuli can be measured, but not the experience itself. To address this problem when assessing the capacity of other species to experience pain, argument by analogy is sometimes used. (yes)

Did you know?

... that, despite its name, the freshwater crab Potamon ibericum (pictured) does not live in Iberia?
... that when the sea anemone Adamsia palliata grows on the exterior of a gastropod shell, it is capable of enlarging the shell to better accommodate the hermit crab Pagurus prideaux inside?
... that Jurellana tithonia, dating from the Jurassic, is the earliest known porcelain crab?
... that several pelagic gooseneck barnacles were once found attached to an American crocodile?

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Thomas Bell FRS (October 11, 1792 – March 13, 1880) was an English zoologist, surgeon and writer, born in Poole, Dorset, UK. Bell, like his mother Susan, took a keen interest in natural history which his mother also encouraged in his younger cousin Philip Henry Gosse. Bell left Poole in 1813 for his training as a dental surgeon in London. He combined two careers, becoming Professor of Zoology at King's College London in 1836 (on the strength of his amateur researches) and lecturing on anatomy at Guy's Hospital. He became a Fellow of the Royal College of Surgeons in 1844. He was President of the Linnean Society in 1858. Bell was at the heart of the scientific establishment and when Charles Darwin returned to London from the Beagle expedition on December 2, 1836, Bell was quick to take on the task of describing the reptile specimens. He was also entrusted with the specimens of crustaceans collected on the voyage. He was the authority in this field; his book British Stalked-eye Crustacea is a masterwork.

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Credit: Hans Hillewaert

Nototropis falcatus (formerly Atylus falcatus) is a species of amphipod from sandy bottoms in the North Atlantic and North Sea.

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