Crab Facts & Trivia: Fascinating Things to Know

Crabs belong to the kingdom Animalia, phylum Arthropoda, class Crustacea, order Decapoda, and family Brachyura, a classification that points straight at their defining trait: ten limbs, including a pair of front claws used for both defense and feeding. Rather than an internal skeleton, a crab wears its skeleton as an exoskeleton on the outside of its body, which is why losing a claw or limb isn't permanent: it simply grows back over time.

That hard shell pairs with a useful shape in many species: a flattened body that lets them squeeze into tight crevices and narrow gaps other sea creatures can't reach.

A crab's senses are just as unusual as its build. Its eyes sit on stalks much like a snail's, and each eye is compound, made of hundreds of tiny lenses. Stranger still, a crab's teeth aren't in its mouth at all — they're located in its stomach.

Diet varies widely across the roughly 5,000 species, with different crabs classified as carnivores, herbivores, or omnivores depending on what's available. They breathe through gills, and reproduction is a numbers game: a single female can release millions of eggs in one go, hatching into larvae no bigger than the head of a pin.

Crabs can walk in any direction, but when they're in a hurry, sideways is their preferred gear, and they can hit speeds of around 12 miles per hour doing it. They typically live three to four years, and they communicate with each other through physical signals: flapping a pincher or knocking their claws together rather than making sounds.

Not every crab fits the standard mold, either. King crabs, despite the name, aren't classified as true crabs at all. Size ranges from tiny pinhead-sized larvae up to the Japanese spider crab, whose leg span can stretch to 12 feet from claw to claw.

The Red Rock crab adds a splash of color, with red, yellow, orange, and white across its shell.

• Crabs are decapod crustaceans, meaning they have ten limbs in total.
• Their shell functions as an exoskeleton, worn on the outside of the body.
• Around 5,000 different crab species have been identified.
• A crab's front two legs end in claws.
• Their compound eyes, perched on stalks, are made of hundreds of tiny lenses.
• Newly hatched crab larvae are only as big as a pinhead.
• One female can lay millions of eggs in a single batch.
• Lost claws and limbs regenerate over time.
• A crab's teeth are located in its stomach, not its mouth.
• Diets range across carnivore, herbivore, and omnivore depending on species.
• King crabs aren't classified as true crabs.
• The Japanese Spider Crab can span 12 feet from claw to claw.
• Crabs typically live three to four years and can move at about 12 mph.
• A group of crabs is called a cast.

Crabs haven't starred in many films, but they've made a couple of memorable appearances: the campy 1957 creature feature Attack of the Crab Monsters and the independent short The Crab Movie from 2010. On the music side, the crab has scuttled into a couple of song titles too, with Weezer releasing a track called "Crab" and Faith No More putting out "The Crab Song."

Pop culture's most famous crab is almost certainly Sebastian, the calypso-singing crustacean from Disney's The Little Mermaid. Nickelodeon fans know Mr. Krabs, the penny-pinching restaurant owner from SpongeBob SquarePants, while comic strip readers may recognize Hawthorne from Sherman's Lagoon. The animated fish tale Shark Tale threw its own crab into the mix with the character Crazy Joe.