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


    Almón B, Pérez Dieste J, Trigo JE. 2013. New contributions on Cumanotus cuenoti Pruvot-Fol, 1948 and Cumanotus beaumonti (Eliot, 1906) (Gastropoda: Flabellinidae) in the Iberian Peninsula. Gloria Maris 52 (1-2): 14-21.
    Anderson RC. 1988. Swimming nudibranchs. Shells & Sea Life 20(1):9-10.
    Austin WC. 1985. An annotated checklist of the marine invertebrates in the cold temperate northeast Pacific. 3 vols., xiv + 682 pp Khoyatan Marine Laboratory.
    Ballesteros M, Madrenas E, Pontes M. 2024. OPK - Opistobranquis. Available from
    Bebbington A, Thompson TE. 1968. Note sur les opisthobranches du Bassin d’Arcachon. Actes de la Societe Linneenne de Bordeaux, ser. A, 105(5):1-35.
    Beeman RD, Williams GC. 1980. Chapter 14. Opisthobranchia and Pulmonata: the sea slugs and allies; pp 308- 354, pls. 95-111, In: Intertidal invertebrates of California, ix + 690 pp, 200 pls. Stanford University Press.
    Behrens DW. 1980. A review of the literature on the opisthobranch fauna of San Francisco Bay. Opisthobranch Newsletter 12(4-12):34-37.
    Behrens DW. 1980. Pacific coast nudibranchs, a guide to the opisthobranchs of the northeastern Pacific. 112 pp, 162 photos. Sea Challengers, Los Osos, Calif.
    Bielecki S, Cavignaux G, Crouzet JM, et al. 2011. Des limaces de rêve.
    Díaz Agras G, Urgorri V, Trigo JE, et al. 2010. New records of Galician opisthobranch molluscs. Communications of the 3 rd. International Workshop on Opisthobranchs. Vigo, Spain.
    Edmunds M. 1991. Does warning coloration occur in nudibranchs. Malacologia 32(2):241-255.
    Eliot CNE. 1908. On the genus Cumanotus. J. Mar. Biol. Assoc. U.K., new series 8(3):313-314.
    Eliot CNE. 1906. Notes on some British nudibranchs. Journal of the Marine Biological Association of the United Kingdom 7 (3): 333-382 giugno.
    Eliot CNE. 1910. A monograph of the British nudibranchiate Mollusca: with figures of the species; Figures by the late Joshua Alder and the late Albany Hancock, and others. Ray Society, London.
    Evertsen J, Bakken T. 2005. Nudibranch diversity (Heterobranchia, Gastropoda) along the coast of Norway. Fauna Norvegica, 25: 1-37.
    Evertsen J, Bakken T. 2013. Diversity of Norwegian sea slugs (Nudibranchia): new species to Norwegian coastal waters and new data on distribution of rare species. Fauna Norvegica 32: 45-52.
    Farmer WM. 1980. Sea-slug gastropods, 177 pp W. m Farmer Enterprises, Tempe, Arizona.
    Garcia FJ, Bertsch H. 2009. Diversity and distribution of the Gastropoda Opisthobranchia from the Atlantic Ocean: A global biogeographic approach. Scientia Marina. 73(1):153–160.
    Høisæter T. 1986. An annotated check-list of marine molluscs of the Norwegian coast and adjacent waters. Sarsia 71(2):73-175.
    Just H, Edmuns M. 1985. North atlantic nudibranchs (Mollusca) seen by Henning Lemche. Ophelia supplement 2: 1-150.
    Long SJ. 2006. Bibliography of Opisthobranchia 1554-2000. Bayside Books & Press, Tustin, CA, U.S.A. 672p.
    McDonald GR. 1983. A review of the nudibranchs of the California coast. Malacologia 24:114-276.
    McDonald G. 2009. Bibliographia Nudibranchia. 2nd Online Edition, Annotated. 1072 pp  Institute of Marine Sciences, University of California, Santa Cruz. Available from
    McDonald G, Nybakken JW. 1997. List of the Worldwide Food Habits of Nudibranchs. Veliger, 40(2). Available from
    Nordsieck F. 1972. Die europäischen Meeresschnecken : (Opisthobranchia mit Pyramidellidae, Rissoacea) : vom Eismeer bis Kapverdem, Mittelmeer und Schawarzes Meer. Stuttgart: Gustav Fischer. XIII, 327 p. p.
    Odhner NHJ. 1910. Some notes on the genus Cumanotus. J. Mar. Biol. Assoc. U.K., new series 9(1):82-84.
    Picton BE. 1991. Cumanotus beaumonti (Eliot, 1906), a nudibranch adapted for life in a shallow sandy habitat. Malacologia 32(2):219-221.
    Picton BE, Morrow C. 1994. Cumanotus beaumonti accessed through: Nudibranchs of the British Isles on 2014-12-14. Available from
    Picton BE, Morrow C. 1994. A Field guide to the Nudibranchs of the British Isles. London: Immel Publishing Ltd. London: 143 pp.
    Prkić J, Petani A, Iglić Ð, et al. 2018. Stražnjoškržnjaci Jadranskoga Mora: Slikovni Atlas i Popis Hrvatskih Vrsta / Opisthobranchs of the Adriatic Sea: Photographic Atlas and List of Croatian Species. Bibinje: Ronilaćki Klub Sveti Roko. 464 p. Available from
    Pruvot-Fol A. 1948. Deux aeolidiens d’Arcachon. Journal de Conchyliologie 88 (3): 97-100.
    Pruvot-Fol A. 1954. Mollusques opisthobranches. Paris, France: Paul Lechevalier (Faune de France). 460 p.
    Roller RA. 1970. A supplement to the annotated list of opisthobranchs from San Luis Obispo county, California. Veliger 12(4):482-483.
    Rudman W.B. et al. 1998 2010. Cumanotus beaumonti accessed through: Sea Slug Forum on 2014-12-14. Available from
    Seaward DR. 1982. Sea area atlas of the marine molluscs of Britain and Ireland. Conchological Society of Great Britain & Ireland / Nature Conservancy Council, 242 pp.
    Sphon GG. 1972. An annotated checklist of the nudibranchs and their allies from the west coast of North America. Opisthobranch Newsletter 4(10-11):53-79.
    Step E. 1945. Shell life. An introduction to the British Mollusca, 443 pp, 32 pls. Frederick Warne & Co., Ltd., London.
    Strathmann MF. 1987. Reproduction and development of marine invertebrates of the northern Pacific coast. Data and methods for the study of eggs, embryos, and larvae. University of Washington Press, xii + 670 pp.
    Tardy J. 1965. Description et biologie de Cerberilla bernadetti, espèce nouvelle de Gastéropode Nudibranche de la côte atlantique française. Discussion sur la position systématique du genre. Bulletin de l’Institut Océanographique de Monaco 65 (1349): 1-22.
    Tardy JP, Gantes H. 1980. Un mollusque nudibranche peu connu: Cumanotus cuenoti A. Pruvot-Fol, (1948); redescription, biology. Bulletin de la Societe Zoologique de France 105(1):199- 207, pls. I-II.
    Thiele J. 1931. Handbuch der systematischen Weichtierkunde 1. Jena (Fischer): i-vi, 1-778, 783 figs.
    Thiele J, Bieler R, Mikkelsen PM. 1992. Handbook of systematic malacology. Washington, D.C.: Smithsonian Institution Libraries : National Science Foundation.
    Thompson TE. 1976. Nudibranchs, 96 pp, 30 pls. T.F.H. Publ., New Jersey.
    Thompson TE. 1976. Biology of opisthobranch molluscs. London: Ray Society (Publications - Ray Society).
    Thompson TE. 1964. Grazing and the life cycles of British nudibranchs, pp 275-297, In: D. J. Crisp (ed ), Grazing in terrestrial and marine environments. British Ecological Society Symposium No. 4, 322 pp Blackwell, Oxford.
    Thompson TE. 1988. Molluscs: benthic opisthobranchs (Mollusca: Gastropoda) keys and notes for the  identification of the species. 2nd ed. Avon, Great Britain: Brill, E. J. & Backhuys, W. (Synopses of the British fauna,). 356 p.
    Thompson TE, Brown GH. 1984. Biology of Opisthobranch Molluscs. Vol. 2. Ray Society, London 156, pp. 229:
    Thompson TE, Brown GH. 1976. British opisthobranch molluscs Mollusca: Gastropoda; keys and notes for the identification of the species. London: Acad. Pr. (Synopses of the British fauna). 203 S. p.
    Todd CD. 1981. The ecology of nudibranch molluscs. Oceanography & Marine Biology Annual Review 19:141-234.
    Trainito E, Doneddu M. 2014. Nudibranchi del Mediterraneo. 2nd. Il Castello. 192 p.

    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: 20/04/2024. Available at (

To copy this cite click on the right button.