Four-striped polycera (Polycera quadrilineata)

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



Polycera quadrilineata may grow up to 3.9 cm, but the maximum recorded length is 4.5 cm. Its body is translucent white with patches of yellow and orange pigments forming five longitudinal lines. Along the mid-line there is a row of oval blotches, merging towards the rear. Occasionally individuals have black streaks, blotches or fine spots on their backs. The front region of the head extends to form an oral veil. The edge of the foot is usually dotted with colour extended into a veil which is usually edged with yellow-orange colour with spots on the flank. The four frontal processes (frontal veil papillae) are coloured yellow. Two sensory organs (rhinophores) are present on its head, they have thick stalks which end with a yellow cylindrical knob. The eggs are spawned in a short white curved ribbon. This species is often found in large numbers.

Recorded distribution in Britain and Ireland

Common all around the British Isles.

Global distribution

Recorded from America to the Mediterranean.


Polycera quadrilineata occurs on encrusting sea mats (Bryozoa) from the intertidal and sublittoral zones to depths of about 60 m.

Depth range


Identifying features

  • Grows up to 3.9 cm.
  • Translucent white with patches of yellow and orange.
  • Five longitudinal lines of varying shades along the back.
  • Four processes on the oral veil.

Additional information

Polycera quadrilineata is sometimes confused with Polycera faeroensis. However Polycera faeroensis has 8 or more oral veil processes whereas Polycera quadrilineata has four, and the patches of yellow pigments on the body are absent from Polycera quadrilineata.

Listed by

- none -


  1. Hayward, P.J. & Ryland, J.S. (ed.), 1995. The marine fauna of the British Isles and north-west Europe. Volume 2. Molluscs to Chordates. Oxford Science Publications. Oxford: Clarendon Press.

  2. 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.]

  3. JNCC (Joint Nature Conservation Committee), 1999. Marine Environment Resource Mapping And Information Database (MERMAID): Marine Nature Conservation Review Survey Database. [on-line]

  4. Picton, B. E. & Morrow, C.C., 1994. A Field Guide to the Nudibranchs of the British Isles. London: Immel Publishing Ltd.

  5. Picton, B.E. & Morrow, C.C., 2000. Encyclopaedia of Marine Life of Britain and Ireland., 2003-09-18

  6. Picton, B.E., 2000. Nudibranchs of the British Isles., 2003-09-11

  7. Thompson, T. E. & Brown, G. H., 1976. British Opisthobranch Molluscs. London: Academic Press. [Synopses of the British Fauna, no. 8.]


  1. Centre for Environmental Data and Recording, 2018. Ulster Museum Marine Surveys of Northern Ireland Coastal Waters. Occurrence dataset accessed via on 2018-09-25.

  2. Conchological Society of Great Britain & Ireland, 2018. Mollusc (marine) data for Great Britain and Ireland - restricted access. Occurrence dataset: accessed via on 2018-09-25.

  3. Conchological Society of Great Britain & Ireland, 2018. Mollusc (marine) records for Great Britain and Ireland. Occurrence dataset: accessed via on 2018-09-25.

  4. Environmental Records Information Centre North East, 2018. ERIC NE Combined dataset to 2017. Occurrence dataset: accessed via on 2018-09-38

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

  6. Fife Nature Records Centre, 2018. St Andrews BioBlitz 2015. Occurrence dataset: accessed via on 2018-09-27.

  7. Manx Biological Recording Partnership, 2018. Isle of Man historical wildlife records 1990 to 1994. Occurrence dataset: accessed via on 2018-10-01.

  8. National Trust, 2017. National Trust Species Records. Occurrence dataset: accessed via on 2018-10-01.

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

  10. OBIS (Ocean Biodiversity Information System),  2024. Global map of species distribution using gridded data. Available from: Ocean Biogeographic Information System. Accessed: 2024-05-18

  11. Outer Hebrides Biological Recording, 2018. Invertebrates (except insects), Outer Hebrides. Occurrence dataset: accessed via on 2018-10-01.


This review can be cited as:

Edwards, R.V. 2008. Polycera quadrilineata Four-striped polycera. 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 18-05-2024]. Available from:

Last Updated: 17/04/2008