Portal:Crustaceans

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The Crustaceans Portal

Abludomelita obtusata.jpg

Crustaceans (Subphylum Crustacea) form a very large group of arthropods, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 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 14 ft (4.3 m) and a mass of 44 lb (20 kg). Like other arthropods, crustaceans have an exoskeleton, which they moult in order 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 the nauplius form of the larvae. Most crustaceans are free-living aquatic animals, but some are terrestrial (e.g. woodlice), some are parasitic (e.g. fish lice, tongue worms) and some are sessile (e.g. barnacles). The group has an extensive fossil record, reaching back to the Cambrian, and includes living fossils such as Triops cancriformis, which has existed apparently unchanged since the Triassic period. More than 10 million tons of crustaceans are produced by fishery or farming for human consumption, the majority of it being shrimps 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.

Selected article

Seychellum alluaudi (Decapoda, Potamonautidae)
Seychellum alluaudi is a species of freshwater crab endemic to the Seychelles, and the only true freshwater crab in that country. It lives in rainforest streams on the archipelago's granitic high islands. Although it may be abundant, little is known about its biology, and it is currently listed as Least Concern on the IUCN Red List. Adults are dark yellow to brown in colour, and have a quadrangular carapace with a width of around 50 mm (2 in). The claws are unequal in size.

S. alluaudi was described as a species of Deckenia in 1893 and 1894, and later split off into the monotypic segregate genus Seychellum. Its closest relatives are the two species currently in Deckenia, both of which are found in East Africa. Several hypotheses have been published to explain how Seychellum reached its isolated location; some means of transport across the open ocean is considered the most likely explanation. Seychellum differs from Deckenia in a number of characters, including the lengths of the legs and antennae, and the fact that Deckenia species have flattened legs, compared to those of Seychellum.

Did you know?

An orange-red lobster-like animal with no claws, seen from the side.

Selected biography

Henri Milne-Edwards
Henri Milne-Edwards (Bruges, October 23, 1800 – Paris, July 29, 1885) was an eminent French zoologist. He was the 27th child of an English father (Wiliam Edwards) and a French mother (Elisabeth Vaux). Henri was born in Bruges, now in Belgium, but then part of the French Republic, and he spent most of his life in France. Henri was brought up in Paris by his older brother William Edwards, a physiologist. After studying medicine in Paris, his passion for natural history prevailed, and he studied the "lower forms" of animal life. He studied under Georges Cuvier and befriended Jean Victoire Audouin. In 1832, Milne-Edwards became professor of hygiene and natural history at the Collège Central des Arts et Manufactures. In 1841, after the death of Audouin, Milne-Edwards succeeded him at the chair of entomology at the Muséum National d'Histoire Naturelle. In 1862, he succeeded Isidore Geoffroy Saint-Hilaire in the long-vacant chair of zoology.

Much of his original work was published in the Annales des sciences naturelles, which he edited from 1834. His Histoire naturelle des Crustacés (1837–1841), long remained a standard work; other works include Histoire naturelle des coralliaires (1858–1860), Leçons sur la physiologie et l'anatomie comparée de l'homme et des animaux (1857–1881), and a work on the elements of zoology, originally published in 1834, but subsequently remodelled, which enjoyed an enormous circulation.

Selected picture

Lithodes santolla (Decapoda: Lithodidae)
Credit: Butterfly voyages

Lithodes santolla, the southern king crab or centolla is a South American species of king crab.

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