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

An acorn barnacle (Perforatus perforatus)

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



Up to 30 mm in diameter and 30 mm tall, Balanus perforatus is recognised by its tapered, volcano-like shape. The shell wall consists of 6 purplish plates that are often vertically ridged, and sometimes separated at the apex leaving a jagged lip. Inside the operculum aperture, the tissue is marked with bright colours of pink, purple and blue. The tergoscutal flaps are brown to purple in colour, with blue and white spots.

Recorded distribution in Britain and Ireland

Balanus perforatus is a southern species extending to south-west England and south Wales but not recorded from Ireland.

Global distribution

Common in the Mediterranean and extending southward to the coasts of Africa and northwards up the Spanish and French coasts to the south-west coasts of Great Britain.


Balanus perforatus is found from the mid-shore to the sublittoral on rocks and artificial structures and is sometimes common in wave exposed situations. Also present on ships' hulls.

Depth range


Identifying features

  • Volcano-like shape.
  • Small oval aperture.
  • Operculum deeply immersed within the aperture.
  • Terga with short, pointed beaks.
  • Base calcareous.

Additional information

Aperture usually very small but quite large in sublittoral specimens.

Listed by

- none -

Further information sources

Search on:


  1. Bassindale, R., 1964. British Barnacles. London: The Linnean Society of London.[Synopses of the British Fauna, no. 14.]

  2. Campbell, A.C., 1982. The Hamlyn guide to the flora and fauna of the Mediterranean Sea. London: Hamlyn.

  3. Fish, J.D. & Fish, S., 1996. A student's guide to the seashore. Cambridge: Cambridge University Press.

  4. Hayward, P., Nelson-Smith, T. & Shields, C. 1996. Collins pocket guide. Sea shore of Britain and northern Europe. London: HarperCollins.

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

  6. Hiscock, K., Southward, A., Tittley, I., Jory, A. & Hawkins, S., 2001. The impact of climate change on subtidal and intertidal benthic species in Scotland. Scottish National Heritage Research, Survey and Monitoring Report , no. 182., Edinburgh: Scottish National Heritage

  7. Howson, C.M. & Picton, B.E., 1997. The species directory of the marine fauna and flora of the British Isles and surrounding seas. Belfast: Ulster Museum. [Ulster Museum publication, no. 276.]


This review can be cited as:

Skewes, M. 2008. Perforatus perforatus An acorn barnacle. In Tyler-Walters H. and Hiscock K. (eds) Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 20-03-2018]. Available from:

Last Updated: 08/05/2008