Xanthidae is a family of crabs known as gorilla crabs, mud crabs, pebble crabs or rubble crabs. Xanthid crabs are often brightly coloured and are highly poisonous, containing toxins which are not destroyed by cooking and for which no antidote is known. The toxins are similar to the tetrodotoxin and saxitoxin produced by puffer fish, and may be produced by bacteria in the genus Vibrio living in symbiosis with the crabs, mostly V. alginolyticus and V. parahaemolyticus.
Libinia is a genus of crabs in the family Epialtidae, containing twelve extant species:
Libystes is a genus of crabs, containing six species:
Macrophthalmus is a genus of crabs which are widespread across the Indo-Pacific. It contains the following species : Species in this genus are often referred to as sentinel crabs.
Cancridae is a family of crabs. It comprises six extant genera, and ten exclusively fossil genera, in two subfamilies:
Belliidae is a family of crabs of the order Decapoda.
Discoplax is a genus of terrestrial crabs. It is very closely related to the genus Cardisoma.
Menippidae is a family of crabs of the order Decapoda.
Ozius is a genus of crabs in the family Menippidae, containing the following species:
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.
Pilumnoidea is a superfamily of crabs, whose members were previously included in the Xanthoidea. The three families are unified by the free articulation of all the segments of the male crab's abdomen and by the form of the gonopods. The earliest fossils assigned to this group are of Eocene age.
Panopeus is a genus of crabs, containing these extant species:
Medaeus is a genus of crabs in the family Xanthidae, containing the following species:
Lachnopodus is a genus of crabs in the family Xanthidae, containing the following species:
Paraxanthias is a genus of crabs in the family Xanthidae, containing one exclusively fossil species and the following extant species:
Xanthias is a genus of crabs in the family Xanthidae, containing two exclusively fossil species and the following extant species:
Atergatis is a genus of crabs in the family Xanthidae, containing the following species:
Lophozozymus is a genus of crabs in the family Xanthidae, containing the following species:
Around 65 species of crab occur in the waters of the British Isles. All are marine, with the exception of the introduced Chinese mitten crab, Eriocheir sinensis, which occurs in fresh and brackish water. They range in size from the deep-water species Paromola cuvieri, which can reach a claw span of 1.2 metres, to the pea crab, which is only 4 mm (0.16 in) wide and lives inside mussel shells.
