page_title: Crab
section_title: Description
hierarchical_section_title: Crab / Description
caption_attribution_description: Gecarcinus quadratus (Halloween crab) at Nosara, Costa Rica
context_page_description: Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail", usually hidden entirely under the thorax. They live in all the world's oceans, in fresh water, and on land, are generally covered with a thick exoskeleton, and have a single pair of pincers. Many other animals with similar names – such as hermit crabs, king crabs, porcelain crabs, horseshoe crabs, and crab lice – are not true crabs.
context_section_description: Crabs are generally covered with a thick exoskeleton, composed primarily of highly mineralized chitin, and armed with a single pair of chelae (claws). Crabs are found in all of the world's oceans, while many crabs live in fresh water and on land, particularly in tropical regions. Crabs vary in size from the pea crab, a few millimeters wide, to the Japanese spider crab, with a leg span up to 4 m (13 ft).
caption: Gecarcinus quadratus, a land crab from Central America
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