Cranch's spider crab (Achaeus cranchii)

Distribution data supplied by the Ocean Biodiversity Information System (OBIS). To interrogate UK data visit the NBN Atlas.Map Help

Summary

Description

A spider crab with characteristic swellings on each side of the carapace, bearing groups of bristles or small spines (hook-setae). The carapace is relatively smooth, narrowed, and grows up to 12 mm long and 8 mm wide. The frontal region produces a small, short, prolongation of the head (rostrum) with a U-shaped incision. Colouration is pale to a reddish-yellow, with lighter chelipeds and pereiopods. The abdomen is separated into 2-5 sections (somites). The pincered legs (chelipeds) are spiny and the walking legs (pereiopods) are covered with long bristles. Chelipeds are spiny, equal and larger in male crabs. The eyestalks are especially long and are always visible. 

Recorded distribution in Britain and Ireland

Recorded from the south and west coasts of Britain.

Global distribution

Scattered records from the British Isles along the northern coast of France to Brussels. Also recorded in the eastern Atlantic and Mediterranean. 

Habitat

Found from 5-70 m on hydroids, bryozoans, ascidians and on undersides of raised boulders, often masked with algae.

Depth range

5-70 m

Identifying features

  • Dorsal surface of carapace relatively smooth with distinctive, swollen, outline.
  • Colouration pale to reddish-yellow
  • Chelipeds spiny, equal.
  • Second to fifth pairs of walking legs slender and covered with long, hook-shaped, setae.

Additional information

The pereopods are shorter than those of Inachus spp. 

Listed by

- none -

Further information sources

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Bibliography

  1. Hanson Aggregates Marine Limited 1998. 1998 Hastings shingle bank : southern England, biological and habitat survey. [on-line] http://www.marlin.ac.uk, 2003-02-22

  2. Hayward, P.J. & Ryland, J.S. (ed.) 1995b. Handbook of the marine fauna of North-West Europe. Oxford: Oxford University Press.

  3. Ingle, R.W., 1980. British Crabs. Oxford: British Museum (Natural History), Oxford University Press.

  4. Ingle, R.W., 1996. Shallow-water Crabs, (2nd edn). Shrewsbury: Field Studies Council. [Synopses of the British Fauna, no 25]

  5. Sanderson, W.G., 1996. Rare benthic marine flora and fauna in Great Britain: the development of criteria for assessment. Joint Nature Conservation Committee, Peterborough. JNCC Report, no. 240.

Datasets

  1. NBN (National Biodiversity Network) Atlas. Available from: https://www.nbnatlas.org.

  2. OBIS (Ocean Biodiversity Information System),  2025. Global map of species distribution using gridded data. Available from: Ocean Biogeographic Information System. www.iobis.org. Accessed: 2025-05-21

Citation

This review can be cited as:

Wilson, E & Gibson-Hall, E 2018. Achaeus cranchii Cranch's spider crab. In Tyler-Walters H. and Hiscock K. Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 21-05-2025]. Available from: https://www.marlin.ac.uk/species/detail/1236

Last Updated: 01/08/2018