Masked crab (Corystes cassivelaunus)

GenusCorystes (1)
SizeCarapace length: 4 cm (2)
Carapace width: 3 cm (2)
Top facts

Common and widespread (3).

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).

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).

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

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).

Not currently threatened.

No conservation action has been targeted at this species.

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:

  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.