Armoured crustaceans with the tail tucked under the body, able to run sideways. The crab shape has evolved several separate times, a process called carcinisation, so crabs aren’t one natural group.
This entry covers a whole group, so the answers describe a typical member. For a specific one, see Hermit crab.
Quick answers
What is it?Crustacean
Carnivore?Omnivore
Dangerous?No
Domesticated?No
Awake when?Day & night
Hibernates?No
Kept as a pet?Sometimes
Mostly hermit crabs, which are commonly kept as pets and can live for 30 years.
Do people eat it?Yes
Crabs make up about 20% of the sea crustaceans caught or farmed for food.
At a glance
Found inOceans, Worldwide
HabitatCoast, Open ocean, Rivers & lakes
ColoursRed, Brown, Orange
SizeSmall
LengthA few mm (pea crab) to a 4 m leg span (Japanese spider crab)
Legs10
Covered inShell
Lives ingroups
Lives for3–30 years
Can swim
Lays eggs
In the wild
- Where it lives
- Oceans worldwide, and a substantial number of species live in fresh water or on land.
- What it eats
- Many are marine omnivores eating algae, molluscs, worms and other crustaceans; others are specialist plant- or meat-eaters.
Did you know
Evolution keeps independently reinventing the crab shape.
Crabs make up about 20% of the sea crustaceans caught or farmed for food.
Often confused with
- Hermit crab
Unlike most crabs, a hermit crab has a soft abdomen that it protects in a borrowed shell.
Compare side by side - Horseshoe crab
Despite its name it is not a crab or even a crustacean: it is a chelicerate, more closely related to spiders, ticks and scorpions.
Compare side by side
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