Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting tail-like abdomen, usually hidden entirely under the thorax. They live in all the world's oceans, in freshwater, and on land, are generally covered with a thick exoskeleton, and have a single pair of pincers on each arm. They first appeared during the Jurassic period, around 200 million years ago.
The little auk (Europe) or dovekieAlle alle is a small auk, the only member of the genus Alle. Alle is the Sami name of the long-tailed duck; it is onomatopoeic and imitates the call of the drake duck. Linnaeus was not particularly familiar with the winter plumages of either the auk or the duck, and appears to have confused the two species. Other old names include rotch, rotche, bullbird, and sea dove, although the latter sometimes refers to a relative, the black guillemot.
King crabs are decapod crustaceans in the family Lithodidae that are chiefly found in deep waters and are adapted to cold environments. They are composed of two subfamilies: Lithodinae, which tend to inhabit deep waters, are globally distributed, and comprise the majority of the family's species diversity; and Hapalogastrinae, which are endemic to the North Pacific and inhabit exclusively shallow waters. King crabs are not true crabs and are generally thought to be derived from hermit crab ancestors within the Paguridae, which may explain the asymmetry still found in the adult forms. This ancestry is supported by several anatomical peculiarities which are present only in king crabs and hermit crabs. Although some doubt still exists about this hypothesis, king crabs are the most widely quoted example of carcinisation among decapods. Several species of king crabs, especially in Alaskan and southern South American waters, are targeted by commercial fisheries and have been subject to overfishing.
Carcinisation is a form of convergent evolution in which non-crab crustaceans evolve a crab-like body plan. The term was introduced into evolutionary biology by L. A. Borradaile, who described it as "the many attempts of Nature to evolve a crab".
Squilla mantis is a species of mantis shrimp found in shallow coastal areas of the Mediterranean Sea and the Eastern Atlantic Ocean: it is also known as "pacchero" or "canocchia". Its abundance has led to it being the only commercially fished mantis shrimp in the Mediterranean.
Lithodes santolla, also known as the southern king crab, Chilean king crab or centolla, is a species of king crab, found off southern South America including the offshore Falkland Islands. On the Pacific side, it is found in Chile from Talcahuano to Cape Horn. On the Atlantic side, it is found off Argentina and Uruguay. It lives in the benthic zone at depths of 0–700 m (0–2,300 ft), with Uruguayan records being exclusively from great depths. In Chile, it mostly lives at depths to 150 m (490 ft), but south of 40° S it can be found to 600 m (2,000 ft). It is a large crab that can reach up to 19 cm (7.5 in) in carapace length, and it is the target of commercial fishing.
Goneplax rhomboides is a species of crab. It is known by the common name angular crab because of its angular carapace. Although it is also called the square crab, its shell is in fact more trapezoidal than square. This species is also known as the mud-runner because they are able to run away quickly when threatened.
Crustaceans may pass through a number of larval and immature stages between hatching from their eggs and reaching their adult form. Each of the stages is separated by a moult, in which the hard exoskeleton is shed to allow the animal to grow. The larvae of crustaceans often bear little resemblance to the adult, and there are still cases where it is not known what larvae will grow into what adults. This is especially true of crustaceans which live as benthic adults, more-so than where the larvae are planktonic, and thereby easily caught.
Pisidia longicornis, the long-clawed porcelain crab, is a species of porcelain crab that lives in the north-eastern Atlantic Ocean. It varies from reddish to white, and grows to a carapace width of 1 cm (0.4 in). It was first named by Carl Linnaeus in 1767, although the etymology remains unclear.
Lithodes is a genus of king crabs. Today there are about 30 recognized species, but others formerly included in this genus have been moved to Neolithodes and Paralomis. They are found in oceans around the world, ranging from shallow to deep waters, but mostly at depths of 100–1,000 m (300–3,300 ft). They are restricted to relatively cold waters, meaning that they only occur at high depths at low latitudes, but some species also shallower at high latitudes. They are medium to large crabs, and some species are or were targeted by fisheries.
Neolithodes is a genus of king crabs, in the family Lithodidae. They are found in all major oceans, both in high and low latitudes. Although there are records from water as shallow as 124 m (407 ft) in cold regions, most records are much deeper, typically 700–2,000 m (2,300–6,600 ft), with the deepest confirmed at 5,238 m (17,185 ft). They are fairly large to large crabs that typically are reddish in color and spiny, although the size of these spines varies depending on species.
Cryptolithodes typicus, often referred to as the butterfly crab or the turtle crab, is a species of lithodid crustacean native to coastal regions of the northeastern Pacific Ocean, ranging from Amchitka Island, Alaska to Santa Rosa Island, California.
Cryptolithodes is a genus of king crabs, containing the following three species:
Albunea carabus is a rare species of "sand crab" or "mole crab" in the family Albuneidae. It lives in shallow, turbulent waters in sandy areas of the tropical eastern Atlantic Ocean and the Mediterranean Sea.
Neolithodes grimaldii, the porcupine crab, is a species of king crab in the family Lithodidae. This large red crab is found in cold deep waters in the North Atlantic and often caught as a bycatch in fisheries for Greenland turbot. As suggested by its common name, the carapace and legs are covered in long spines.
Paralomis zealandica, also known as the prickly king crab, is a species of king crab which lives at a depth between 254–1,212 m (833–3,976 ft) in New Zealand. It has a spiky carapace.
Lithodes confundens is a species of king crab. It is found on muddy bottoms off the southern coasts of South America from a depth of 0–283 m (0–928 ft).
Lithodes ferox, also known as the fierce king crab, is a species of king crab. It has been found on the muddy bottoms of the southeastern Atlantic Ocean at depths from 160–1,013 m (525–3,323 ft). It is distributed between the Gulf of Guinea, the northwesternmost coast of South Africa, and the island of Saint Helena.
Lithodes murrayi, also known as the subantarctic stone crab, is a species of king crab. It lives near islands in the southwestern Indian Ocean on muddy bottoms at depths of 35–1,015 m (115–3,330 ft).
