Masked crab (Corystes cassivelaunus)

Masked crab adult, on sandy seabed

Top facts

  • Also known as the sand crab, the masked crab is found on sandy shores and occurs up to depths of around 100 metres.
  • When burrowed under the sand, the masked crab breathes by using its antennae to form a tube.
  • The masked crab preys on other burrowing invertebrates including polychaete worms and bivalve molluscs.
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Masked crab fact file

Masked crab description

GenusCorystes (1)

The masked crab (also known as the sand crab) has an elongated carapace, which is reddish brown to yellow in colour, and sometimes features patterns that look like a face (2). The bristly antennae are considerably longer than the carapace. The first pair of 'pereopods' (walking limbs) have pincers, and are roughly twice the length of the carapace in males, but are about the same length as the carapace in females (3).

Carapace length: 4 cm (2)
Carapace width: 3 cm (2)

Masked crab biology

The masked crab burrows backwards into the sand. Once it is in the sand, the crab forms a tube by fusing the bristles of the second pair of antennae together; it then draws water down this tube for respiration (3). It feeds on burrowing invertebrates, such as polychaete worms and bivalve molluscs (3). Females carry eggs for around 10 months, and can reproduce repeatedly for several years (3).


Masked crab range

Found on many coasts around Britain, but does not occur in most of northern Scotland (2). Elsewhere, the masked crab occurs as far north as Sweden (3).

You can view distribution information for this species at the National Biodiversity Network Atlas.

Masked crab habitat

Found on sandy beaches from the lower shore to depths of around 100m (2).


Masked crab status

Common and widespread (3).


Masked crab threats

Not currently threatened.


Masked crab conservation

No conservation action has been targeted at this species.

There may be further information about this species available via the National Biodiversity Network Atlas.

Find out more

For more on this species see the Marine Life Information Network species account, available at:



This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:



Pair of sensory structures on the head of invertebrates.
The top shell of a turtle. In arthropods (insects, crabs etc), the fused head and thorax (the part of the body located near the head) also known as ‘cephalothorax’.


  1. National Biodiversity Network Species Dictionary (January, 2003)
  2. Skewes, M. 2001. Corystes cassivelaunus. Masked crab. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth:Marine Biological Association of the United Kingdom. (November, 2002)
  3. Fish, J.D. and Fish, S. (1996) A student's guide to the seashore. Second Edition. Cambridge University Press, Cambridge.

Image credit

Masked crab adult, on sandy seabed  
Masked crab adult, on sandy seabed

© Steve Trewhella /

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