🐾 Crab

Crab

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Who it is

• Scientific name: Infraorder Brachyura
• Family & relatives: Crabs are crustaceans, closely related to lobsters, shrimp, and hermit crabs.
• How to spot it: A crab has a wide, flat body shell, a folded tail tucked under its belly, and one pair of pinching claws in front.

Its body & abilities

• Size: Crabs range from pea-sized pea crabs to giant Japanese spider crabs with a leg span of several feet.
• Weight: Most crabs weigh only a few ounces, though the largest kinds can weigh several pounds.
• Body & adaptations: A crab has a hard outer shell called a carapace, ten legs total, stalked eyes, and gills for breathing.
• Top speed: Crabs are famous for scuttling sideways, which is often quicker than moving forward.
• Strength: Their claws are strong tools for crushing shells, grabbing food, and defending themselves.
• Senses: Crabs see with compound eyes on stalks and taste and smell the water using tiny hairs on their legs and antennae.
• Growing up: Crabs hatch as tiny floating larvae, drift as plankton, then settle and molt many times as they grow.

Where it lives

• Habitat: Crabs live in oceans, on rocky shores, in mangroves, and some kinds live in fresh water or on land.
• Where in the world: Crabs are found in seas all over the world, from tropical reefs to cold polar waters.
• Territory: Many crabs hide in burrows or rock crevices and defend their shelter from other crabs.

What it eats

• Diet: Most crabs are omnivores, eating whatever they can find on the sea floor.
• Favorite foods: They eat algae, worms, clams, snails, small fish, and bits of dead animals and plants.
• How it hunts: A crab uses its claws to pick up food, tear it apart, and pass it to its mouth.

How it behaves

• How it moves: Crabs walk and scuttle sideways on their eight walking legs, and some can swim with paddle-shaped back legs.
• When it is active: Many crabs are most active at night or when the tide covers their home.
• Family life: Some crabs live alone, but others gather in huge groups, like the millions of red crabs on Christmas Island.
• How it talks: Male fiddler crabs wave their one giant claw to signal and attract mates.
• Babies: Females carry thousands of fertilized eggs under their tail flap until the larvae hatch into the water.

Its place in nature

• Role in nature: Crabs are cleaners of the sea floor and important food for fish, birds, octopuses, and people.
• Conservation: Many crabs are common, but overfishing and habitat loss threaten some kinds.
• Dangers: Fish, octopuses, sea birds, and larger crabs eat crabs, and they are most at risk right after molting.

Life & legacy

• How long it lives: Small crabs may live a few years, while larger species can live over ten years.
• In our culture: Crabs appear in the zodiac sign Cancer and are a favorite seafood around the world.
• Where to see it: Look for crabs in tide pools, under rocks at the beach, on docks, and in aquariums.
• Fun fact: A crab can drop off a leg or claw to escape a predator and then grow a new one back.