Crabs are generally covered with a thick exoskeleton, composed primarily of highly mineralized chitin. Behind their pair of chelae (claws) are six walking legs and then two swimming legs. The crab breathes See more

Crabs typically walk sideways (hence the term crabwise), because of the articulation of the legs which makes a sidelong gait more efficient. Some … See more

Fisheries
Crabs make up 20% of all marine crustaceans caught, farmed, and consumed worldwide, amounting to 1.5 million tonnes annually. One species, Portunus trituberculatus, accounts for one-fifth of that total. … See more

Crabs are found in all of the world's oceans, as well as in fresh water and on land, particularly in tropical regions. About 850 species are freshwater crabs. See more

Crabs often show marked sexual dimorphism. Males often have larger claws, a tendency that is particularly pronounced in the See more

Crabs attract a mate through chemical (pheromones), visual, acoustic, or vibratory means. Pheromones are used by most fully aquatic crabs, while terrestrial and semiterrestrial crabs … See more

The earliest unambiguous crab fossils date from the Early Jurassic, with the oldest being Eocarcinus from the early Pliensbachian of … See more