Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (= short, ουρά/οura = tail), or where the reduced abdomen's entirely hidden under the thorax. They're generally covered with a thick exoskeleton, and armed with a single pair of chelae (claws). 6,793 species are known. Crabs are found in all of the world's oceans. Additionally, there're also many freshwater and terrestrial crabs, particularly in tropical region… (More on Crab)