A sea slug (Palio nothus)

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



Palio nothus grows up to 2 cm in length and is blackish-green in colour with pale patches. It has cone-like (conical) projections on its back and also short club shaped pimple-like projections (papillae) on either side of the gills. The eggs spawn to forms a coiled ribbon which is white or pale pink in colour. Sensory organs (rhinophores) have long shafts and few lamellae (gill like structures).

Recorded distribution in Britain and Ireland

Common throughout the British Isles.

Global distribution

Recorded all around the British Isles and north to the Arctic circle and to America.


Palio nothus occurs under rocks on the low shore and in the shallow subtidal.

Depth range


Identifying features

  • Grows up to 2 cm in length.
  • Blackish-green colour with pale patches.
  • Transparent cone shaped projections on its body.

Additional information

Palio dubia has been confused with this species in the past, however Palio nothus has a more oval shape head, and club-like dorsal projections, where Palio dubia has rounded processes on its body.

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] http://www.jncc.gov.uk/mermaid

  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., 2000. Nudibranchs of the British Isles. http://www.pictonb.freeserve.co.uk/nudibranchs/index.html, 2003-09-11


  1. Centre for Environmental Data and Recording, 2018. Ulster Museum Marine Surveys of Northern Ireland Coastal Waters. Occurrence dataset https://www.nmni.com/CEDaR/CEDaR-Centre-for-Environmental-Data-and-Recording.aspx accessed via NBNAtlas.org on 2018-09-25.

  2. Conchological Society of Great Britain & Ireland, 2018. Mollusc (marine) records for Great Britain and Ireland. Occurrence dataset: https://doi.org/10.15468/aurwcz accessed via GBIF.org on 2018-09-25.

  3. Fenwick, 2018. Aphotomarine. Occurrence dataset http://www.aphotomarine.com/index.html Accessed via NBNAtlas.org on 2018-10-01

  4. Manx Biological Recording Partnership, 2017. Isle of Man wildlife records from 01/01/2000 to 13/02/2017. Occurrence dataset: https://doi.org/10.15468/mopwow accessed via GBIF.org on 2018-10-01.

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

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


This review can be cited as:

Edwards, R.V. 2008. Palio nothus A sea slug. 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: https://www.marlin.ac.uk/species/detail/1980

Last Updated: 24/04/2008