Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (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.
Hermit crabs are anomuran decapod crustaceans of the superfamily Paguroidea that have adapted to occupy empty scavenged mollusc shells to protect their fragile exoskeletons. There are over 800 species of hermit crab, most of which possess an asymmetric abdomen concealed by a snug-fitting shell. Hermit crabs' soft (non-calcified) abdominal exoskeleton means they must occupy shelter produced by other organisms or risk being defenseless.
The Japanese spider crab 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. The Japanese name for this species is taka-ashi-gani,, literally translating to “tall legs crab”. It goes through three main larval stages along with a prezoeal stage to grow to its great size.
King crabs are a taxon of decapod crustaceans that are chiefly found in cold seas. Because of their large size and the taste of their meat, many species are widely caught and sold as food with the most common being the red king crab.
The crab-eating fox, also known as the forest fox, wood fox, bushdog or maikong, is an extant species of medium-sized canid endemic to the central part of South America since at least the Pleistocene epoch. Like South American foxes, which are in the genus Lycalopex, it is not closely related to true foxes. Cerdocyon comes from the Greek words kerdo and kyon (dog) referring to the dog- and fox-like characteristics of this animal.
Cancer is a genus of marine crabs in the family Cancridae. It includes eight extant species and three extinct species, including familiar crabs of the littoral zone, such as the European edible crab, the Jonah crab and the red rock crab. It is thought to have evolved from related genera in the Pacific Ocean in the Miocene.
Calappa is a genus of crabs known commonly as box crabs or shame-faced crabs. The name box crab comes from their distinctly bulky carapace, and the name shame-faced is from anthropomorphising the way the crab's chelae (claws) fold up and cover its face, as if it were hiding its face in shame.
The graceful rock crab or slender crab, Metacarcinus gracilis or Cancer gracilis, is one of only two members of the genus Metacarcinus, recognized by WoRMS, whose chelae (claws) are white tipped, the other crab being M. magister. Both of these eastern Pacific crab species are recognized by ITIS as belonging to the much larger genus Cancer. M. gracilis has been caught from Alaska to Bahía Magdelena, Baja California. Although M. gracilis is only found in the Pacific Ocean, it has cousins in the Atlantic Ocean. The genus Cancer apparently evolved in the Pacific Ocean and later migrated to the Atlantic Ocean. Larvae and small juveniles of this species are often seen riding jellyfish, especially Phacellophora camtschatica. The juvenile crabs steal food from the jellyfish and also clean off parasitic amphipods.
Cardisoma is a genus of large land crabs. Three species formerly placed in this genus are now placed in Discoplax. The four species that remain in Cardisoma are found in warm coastal regions where they live in burrows. Young individuals are often very colourful with a purple-blue carapace and orange-red legs, but as they grow older the colours tend to fade, and females may be duller than males. Although less extreme than in fiddler crabs, one claw is usually considerably larger than the other. They are omnivores, but primarily feed on plant material.
Menippe is a genus of true crabs. One of the best known species is the Florida stone crab. Most of the species of this genus are found in the Atlantic Ocean.
Gecarcinus is the type genus of the land crab family Gecarcinidae. They are found in warmer coastal regions of the Americas, including islands in the Caribbean. Four species from oceanic islands were formerly included in Gecarcinus as the subgenus Johngarthia, but are now treated as a separate genus, Johngarthia. While all members of this genus are largely terrestrial, they have to return to the ocean to breed. They are often colourful, with reddish, orange, purple, yellowish, whitish, or blackish being the dominating hues. This has resulted in some species, notably G. quadratus and G. lateralis, gaining a level of popularity in the pet trade.
Johngarthia is a genus of crabs in the land crab family Gecarcinidae, formerly included in the genus Gecarcinus, and containing six species. The genus bears the name of John S. Garth, a 20th century naturalist who specialized in crabs and other arthropods.
Latreilliidae is a small family of crabs. They are relatively small, long-legged crabs found on soft bottoms at depths of up 700 metres (2,300 ft) in mostly tropical and subtemperate waters around the world. Their carapace is very small and doesn’t cover the bases of their legs, which protrude from the cephalothorax in a spider-like manner. The family and its type genus are named after Pierre André Latreille. The oldest known fossils from the Latreillidae have been dated to the middle of the Cretaceous period. It comprises seven extant species.
Lybia is a genus of small crabs in the family Xanthidae. Their common names include boxer crabs, boxing crabs and pom-pom crabs. They are notable for their mutualism with sea anemones, which they hold in their claws for defense. In return, the anemones get carried around, which may enable them to capture more food particles with their tentacles. Boxer crabs use at least three species of anemones, including Bundeopsis spp. and Triactis producta. The bonding with the anemone is not needed for survival, however, and boxer crabs have frequently been known to live without them, sometimes substituting other organisms such as sponges and corals for the sea anemones.
Deckenia is a genus of freshwater crabs from East Africa, in the family Potamonautidae, or sometimes in a family of its own, Deckeniidae. The genus was named by Hilgendorf after Karl Klaus von der Decken who collected the first examples during his expeditions to Africa. Both species live in swamps from Eyl in Somalia to Dar es Salaam, Tanzania, both in coastal areas and further inland. A third species, Deckenia alluaudi, lives in the Seychelles, and has been transferred to a separate genus, Seychellum.
Gecarcinus ruricola is a species of terrestrial crab. It is the most terrestrial of the Caribbean land crabs, and is found from western Cuba across the Antilles as far east as Barbados. Common names for G. ruricola include the purple land crab, black land crab, red land crab, and zombie crab.
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.
Periclimenes dardanicola is a species of shrimp found in the western Pacific Ocean. It lives in association with sea anemones that live on the gastropod shells carried by hermit crabs. It was first named by Alexander J. Bruce and Junji Okuno in 2006. It is mainly white, and grows up to a carapace length of 4 mm (0.16 in).
Austin Beatty Williams was an American carcinologist, "the acknowledged expert on and leader in studies of the systematics of eastern American decapod crustaceans".
