Invertebrates
Spiny Spider Crab
Maja brachydactyla · also called European spider crab
In late summer in shallow water off the Cornish coast, spiny spider crabs gather in heaps, hundreds of long legs tangled together as they moult.
Overview
The spiny spider crab, Maja brachydactyla, is a large, long-legged crab of rocky ground, weed, and sandy seabeds along the Atlantic coasts of western Europe. Its spiny shell, decorations, and mass gatherings make it one of the most spectacular crabs in European waters.
A crab that meets for a party
During the moult, the crabs pile up in large numbers, which helps to protect their soft new shells until they harden.
Status
Not Evaluated, but widespread.
Spiny Spider Crab: common questions
Why do spider crabs decorate their shells?
They cover their shells with seaweed, sponges, and other living things, which helps to camouflage them among the rocks and weed.
Why do spider crabs gather in piles?
Large numbers gather in piles in shallow water to moult and mate, which makes them safer from predators while their new shells harden.
How big is the spiny spider crab?
Its shell is up to about 20 cm across, and its leg span can exceed half a metre.
Where is the spiny spider crab found?
It lives on rocky ground, weed, and sandy seabeds of the north-eastern Atlantic, from the British Isles to West Africa.