Not a crab at all but a relative of spiders and scorpions, little changed for about 250 million years. Four species survive: one on the Atlantic coast of the US and Mexico, and three in South, Southeast and East Asia. It lives on the seabed but can swim, and comes ashore to spawn.
Quick answers
What is it?Arachnid
Carnivore?Omnivore
Dangerous?No
Domesticated?No
Awake when?Night
Its eyes become a million times more sensitive to light at night than by day.
Hibernates?No
Kept as a pet?No
Do people eat it?In places
Eaten as a delicacy in parts of Asia; in the United States it is caught for fishing bait and for its blood.
At a glance
Found inOceans, North America, Asia
HabitatCoast
ColoursBrown, Grey
SizeSmall
LengthUp to 79.5 cm with the tail (tri-spine horseshoe crab)
WeightLargest females up to 4–4.8 kg
Legs10
Covered inShell
Lives ingroups
Lives for20–40 years
Can swim
Lays eggs
In the wild
- Where it lives
- The Atlantic coast of the United States and the Gulf of Mexico, plus coasts of South, Southeast and East Asia.
- What it eats
- Worms, clams and other molluscs on the seabed, and sometimes crustaceans and small fish. It forages mostly at night.
Did you know
Its blue blood is used to test medicines for bacterial contamination.
Its blood is blue because it carries oxygen with copper-based hemocyanin instead of iron-based haemoglobin.
Its eyes are a million times more sensitive to light at night than during the day.
Often confused with
- 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.
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