Velvet swimming crab  (Necora puber)

Not threatened (3).

The fast-moving velvet swimming crab has a flattened carapace, which is wider than it is long (2). The upper surface is blue but has a reddish-brown velvety covering, which disguises the blue colouration and earns the species its common name (3). The pincers are equal in size and are also velvety and the eyes are bright red (3). The colour of these eyes and the general aggressive nature of this species may explain the alternative names of Devil crab and witch crab. Between the eyes there are around ten narrow teeth on the edge of the carapace (4).

This crab has a wide distribution in north-west Europe (2). It is common around all coasts of Britain (4).

Small individuals are found on rocky shores at low water but larger specimens occur down to depths of 80 m (2). It is most numerous on fairly sheltered shores (3).

The velvet swimming crab is a fast-moving and very aggressive species (5) and can deliver a painful nip (4). Females carrying eggs can be found at all times of the year in Britain. The adults feed on brown seaweeds, molluscs and crustaceans, whereas juveniles feed mainly on crustaceans such as small crabs and barnacles (2). In some parts of Europe, this species is fished commercially (4).

This species is not threatened.

Conservation action is not required for this species at present.

For more on this crab, see the Marine Life Information Network species account, available on-line at:
http://www.marlin.ac.uk/species/Necorapuber.htm

• Carapace: 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’.
• Crustaceans: diverse group of arthropods (a phylum of animals with jointed limbs and a hard chitinous exoskeleton) characterised by the possession of two pairs of antennae, one pair of mandibles (parts of the mouthparts used for handling and processing food) and two pairs of maxillae (appendages used in eating, which are located behind the mandibles). Includes crabs, lobsters, shrimps, slaters, woodlice and barnacles.

1. National Biodiversity Network Species Dictionary (January2004): http://www.nhm.ac.uk/nbn
2. Fish, J. D. & Fish, S. (1996) A student’s guide to the seashore. Second Edition. Cambridge University Press, Cambridge.
3. Wilson, E., 1999. Necora puber. Velvet swimmer crab. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom (February 2004) http://www.marlin.ac.uk/species/Necorapuber.htm
4. Gibson, R., Hextall, B. & Rogers, A. (2001) Photographic guide to the sea and shore life of Britain and north-west Europe . Oxford University Press, Oxford.
5. Buczacki, S (2002) Fauna Britannica. Hamlyn, London.