The Marine Life Information Network

Information on the biology of species and the ecology of habitats found around the coasts and seas of the British Isles


Henslow's swimming crab (Polybius henslowii)

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



Polybius henslowii is reddish-brown with a roughly circular carapace up to 4.5 cm across with broad spines along the front edge of the rim. Unlike other swimming crabs, which only have the fifth pair of walking legs adapted for swimming, Polybius henslowii has all four walking legs flattened and fringed with hairs. As a result this species is a more active swimmer than other swimming crabs, and sometimes will form swarms at the surface.

Recorded distribution in Britain and Ireland

Recorded from the Shetlands and the south and west coasts of Britain and Ireland.

Global distribution



Polybius henslowii may be found on sand or gravel sediments down to 500 m. As an active swimmer Polybius henslowii can also be found swimming at the surface, often in large numbers, feeding on sardines, squid and other pelagic animals.

Depth range


Identifying features

  • Carapace roughly circular in outline.
  • Propodus and dactylus of all walking legs flattened and fringed with hairs.
  • Dactylus of fifth pair of walking legs paddle shaped, propodus with large rounded distal lobe.

Additional information

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Listed by

- none -



    1. Fenwick, 2018. Aphotomarine. Occurrence dataset Accessed via on 2018-10-01

    2. Isle of Wight Local Records Centre, 2017. IOW Natural History & Archaeological Society Marine Invertebrate Records 1853- 2011. Occurrence dataset: accessed via on 2018-09-27.

    3. NBN (National Biodiversity Network) Atlas. Available from:

    4. OBIS (Ocean Biodiversity Information System),  2023. Global map of species distribution using gridded data. Available from: Ocean Biogeographic Information System. Accessed: 2023-03-28


    This review can be cited as:

    Hosie, A.M. 2009. Polybius henslowii Henslow's swimming 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 28-03-2023]. Available from:

    Last Updated: 21/01/2009