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. They first appeared during the Jurassic Period.
Eriocheir is a genus of crabs, including the Chinese mitten crab, E. sinensis. Formerly in the family Grapsidae, it is now placed in the Varunidae.
Carcinus is a genus of crabs, which includes Carcinus maenas, an important invasive species, and C. aestuarii, a species endemic to the Mediterranean Sea.
The Grapsidae are a family of crabs known variously as marsh crabs, shore crabs, or talon crabs. The family has not been confirmed to form a monophyletic group and some taxa may belong in other families. They are found along the shore among rocks, in estuaries, marshes, and in some cases pelagic among drifting seaweeds and flotsam.
Hemigrapsus sexdentatus, also called the “common rock crab” or “common shore crab,” is a marine crab indigenous to the southern shores of New Zealand. This crab is a member of the Varunidae family in the order Decapoda.
Hemigrapsus crenulatus, the hairy-handed crab or papaka huruhuru, is a marine crab of the family Varunidae, endemic to the New Zealand coast, although a taxon in Chile may be conspecific. It is an intertidal species with semi-terrestrial tendencies. They are named by their characteristic setae, or patches of thick hair, on the chelipeds and legs. They can range from green to brown in coloration. Adult crabs are generally 2–4 cm (0.8–1.6 in) wide at the carapace, although the smallest mature crabs can be around just 1 cm (0.4 in) wide. and are able to survive and reproduce in environments of widely varying salinities.
The tunnelling mud crab, Austrohelice crassa, is a marine large-eyed crab of the family Grapsidae, endemic to the sea coasts of New Zealand. Their carapace width is up to 40 mm.
Hemigrapsus sanguineus, the Japanese shore crab or Asian shore crab, is a species of crab from East Asia. It has been introduced to several other regions, and is now an invasive species in North America and Europe. It was introduced to these regions by ships from Asia emptying their ballast tanks in coastal waters.
The Varunidae are a family of thoracotrematan crabs. The delimitation of this family, part of the taxonomically confusing Grapsoidea, is undergoing revision. For a long time, they were placed at the rank of subfamily in the Grapsidae, but they appear to be closest to Macropthalmus and the Mictyridae, which are usually placed in the Ocypodoidea. It may thus be better to merge the latter superfamily with the Grapsoidea, retaining the latter name as it is older.
Chiromantes haematocheir is a mudflat crab of the family Sesarmidae, which is endemic to East Asia. It is known under the common names red-clawed crab or akategani (Japanese) and the Latin names Grapsus haematocheir and Sesarma haematocheir. It is quite distinct from the other species placed in the genus Chiromantes, and the genus may be restricted to this one species.
Helice tridens is a species of crab which lives on mudflats around the coasts of Japan and the Korean Peninsula.
Johora singaporensis, the Singapore stream crab or Singapore freshwater crab, is a critically endangered species of freshwater crab endemic to Singapore. It grows to a size of 30 millimetres (1.2 in) wide.
Carpilius convexus, commonly known as the marbled stone crab, is a species of crab found in the Indo-Pacific, from Hawaii to the Red Sea and South Africa. It was first described by Peter Forsskål in 1775 as "Cancer convexus", and has sometimes been treated as a variety of the larger species Carpilius maculatus. The biology of the genus Carpilius is poorly known. The coloration of Carpilius convexus is a yellow-brown or red, with patches that are mainly brown, growing up to 25 cm. Despite us knowing their size, coloration, and habitat, little else is known about their biology.
Achaeopsis spinulosa, the hotlips spider crab, is a species of crab in the family Inachidae, found only around the South African coast. It is the only species in the genus Achaeopsis.
Hemigrapsus is a genus of varunid crabs comprising thirteen species native almost exclusively in the Pacific Ocean, but two have been introduced to the North Atlantic region.
Cyanagraea praedator is a species of crab that lives on hydrothermal vents, and the only species in the genus Cyanagraea.
Neohelice granulata is a species of crab in the family Varunidae, and the only species in the genus Neohelice. In 2009, it was estimated that N. granulata was the sixth most studied species of crab.
Ocypode convexa, commonly known as the golden ghost crab, or alternatively the western ghost crab or yellow ghost crab, is a species of ghost crabs endemic to the coast of Western Australia, from Broome to Perth. They are relatively large ghost crabs, with a carapace growing up to 45 mm (1.8 in) long and 52 mm (2.0 in) wide. They are easily recognisable by their golden yellow colouration. Like other ghost crabs they have box-like bodies with unequally sized claws. They also have large eyestalks with the cornea occupying most of the bottom part.
Pseudohelice subquadrata is a species of crab in the family Varunidae. It is found from the eastern Indian Ocean to the western Pacific Ocean, north to Japan, south to Eastern Australia, east to French Polynesia, west to Indonesia and Thailand. It lives near mangroves, burrowing in firm soils, firm muddy sand or loose stones. Burrows are towards or above the high tide line on shores of estuaries and near river mouths of bays, and can have offshoots horizontal beneath the surface as long as three metres.
Helopgrapsus haswellianus or Haswell’s shore crab, is the sole species of crab in the genus Helograpsus. It lives in river mouths and bays on the eastern coast of Australia. The carapace is strongly convex with one distinct notch behind the eye. Adult males have larger claws than adult females. The carapace is olive, dark slate grey or reddish. Claws of adult males are orange-yellow. Carapace size is up to 30 mm wide. The orange color is stronger when these crabs live in habitat with lower pollution levels.
