Cumanotus beaumonti

Cumanotus beaumonti (Eliot, 1906)

Cumanotus beaumonti by Gilles Cavignaux










































Cumanotus beaumonti  (Eliot, 1906)

 Classification according to Bouchet et al. (2017)
Taxonomic source: World Register of Marine Species (AphiaID: 139431).

  • Coryphella beaumonti Eliot, 1906
  • Cumanotus laticeps Odhner, 1907

Specimens of this rare and unusual species of aeolidacean can reach up to 3 cm of length. The general body colouration is reddish or pinkish, more or less clear according to the animal’s feeding. The head is quite wide and has two very short oral tentacles. The rhinophores are smooth and are close together at the base, their colour is somewhat clearer than the rest of the body and may have whitish scores. The most characteristic trait of this species, like the other two known species of the genus, are the very long, narrow cerata. The front-most cerata point forward, the intermediate ones point to the sides, and the rear ones point backwards, giving the animal a “thorny” look. In an animal 20 mm in length, the longest cerata could reach 15 mm long (Thompson & Brown, 1984). There are up to 8 rows of cerata on each side of the notum with 6-9 cerates in each row; The front most 2-3 rows of cerata are located in front of the base of the rhinophores. The cerata are coloured like the body, they are semi-transparent and usually have whitish scores on their surface. Inside the cerata the digestive gland is reddish, purplish or with a slight tinge of green. The tip of the cerata is sharp and whitish and has a long cnidosac. The foot is very wide and semitransparent, forming two short propodial tentacles at the front, while at the rear part forms a short and tappered tail.

This species lives in shallow depths, mainly on sand or gravel bottoms, where athecate hydroids such as Corymorpha nutans grow. In British waters it is thought to feed on this species (Thompson & Brown, 1984). In Galicia, however, it has been reported feeding on other athecate hydroid species such as Ectopleura larynx (Almón et al. 2013). Turk (2005) reported to have found specimens of this species in Northern Adriatic almost buried in mud bottoms at 20 m depth, resembling small anemones. C. beaumonti is able to perform swimming movements thanks to the vigorous movement of its long cerata, a trait that could be used by the animal to move around and explore other feeding sources when the one it was predating is finished. The spawn consists of a spiral wound cord of several turns with white eggs, which is laid on the same mass of hydrozoans it is feeding on or on the sandy bottom where it is held by a peduncle.


  • Cumanotus. From Greek “kyma”, wave + “noton”, back, dorsum.
  • Beaumonti. Dedicated to Walter Ibbotson Beaumont (1861-1912), British faunist who wrote articles about nemerteans, schizopodes (Mysidacea) and nudibranchs and had ornithological interests.

Initially described for the British coasts (Plymouth, Eliot, 1906), it has also been found in Norway (Odhner, 1907, as C. laticeps), in Northern Ireland (Picton, 1991), on the Dutch coast (2010, W. Schepers in Medslugs, 2017), in Slovenia (Turk, 2005), in the North Adriatic (2006, C. Magnani in Medslugs, 2017) and in the French Mediterranean coast (Cagnes-sur-Mer) Horst in Medslugs, 2017). In the Iberian Peninsula it has been located in the Ria de Arousa (Galicia) on the surface of experimental fishfarm cages of salmon from Norway and possibly this has been the introduction vector for the species in Spain (Almón et al. 2013).

Known georeferenced records of the species: Cumanotus beaumonti
: GROC 2010-2011
: Enric Madrenas
: João Pedro Silva
: Bernard Picton
: Manuel Ballesteros.
: M@re Nostrum
: Altres fonts
: Marine Regions


    Western Mediterranean: ☆☆☆☆☆
    Eastern Mediterranean: ☆☆☆☆☆
    Atlantic Ocean: ★☆☆☆☆

This chart displays the monthly observation probability for Cumanotus beaumonti based on our own records.

More pictures


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    Bibliography based on the works by Steve Long, 2006. Bibliography of Opisthobranchia 1554-2000 and Gary McDonald, 2009. Bibliographia Nudibranchia, with later updates from other resources.

Further reading

Cite this article as:

Ballesteros, M., Madrenas, E. & Pontes, M. (2023) "Cumanotus beaumonti" in OPK-Opistobranquis. Published: 13/09/2014. Accessed: 30/09/2023. Available at (

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