Tethys fimbria

Tethys fimbria Linnaeus, 1767

Tethys fimbria @ Badalona (Spain) by Enric Madrenas










































Tethys fimbria  Linnaeus, 1767

 Classification according to Bouchet et al. (2017)
Taxonomic source: World Register of Marine Species (AphiaID: 141643).

  • Tethys cornigera Macri, 1816 
  • Tethys fimbriata 
  • Tethys leporina Linnaeus, 1758 
  • Tethys parthenopeia Macri, 1816
  • Tethys polyphylla Macri, 1816 

It is a large size species since larger animals can reach over 20 cm in length, although about 40% of its length is due to the large cephalic veil. This veil is very broad and of semicircular contour and its outer margin is provided with numerous short threadlike structures, the fimbriae, the reason for its specific name. The margin of the veil also is pigmented with a dark band, decreasing towards the posterior margin. In the lower side and the center of the head, there is the mouth, provided with two thick tuberculate lips; tubercles of mouth and buccal lips are conic shaped and under binocular microscope shows that their own surface is also tuberculate. The mouth has no radula. The general coloration of the animal is grayish-white, with some shades of cream due to the internal viscera. The head, right in the area where it attaches to the cephalic veil, has a couple of short rhinophores with a laminar portion surrounded by a tubular rhinophoric sheath with a membranous extension inside. The mantle of the animal is far smaller than the foot, widely visible from the sides and the rear side. On both sides of the back there are thick flattened cerata (called Phaenicurus) of variable size and finished in one or two tips, of the same colour of the body but with brown-blackish spots. These cerata are easily detached from the body (autotomy) when the animal is disturbed and then they are regenerated. Each cerata has nerves, blood vessels and branches of the digestive gland. Among every two papilla there are two branched appendages gill-like, the first one somewhat larger than the second. The foot is very wide and the same color as the body, with whitish streaks in its dorsal area, running along it. Ventral foot is coloured creamy yellow and in the middle and posterior zone an elongated pedia gland is clearly seen. The anal papilla is located on the front right of the dorsum. Genital orifice is located on the right of the body, slightly behind that side rhinophore; genital papilla is extended backwards by a thin membrane and the penis, about 7 mm in length, is thin and with a curved tip.

This species of nudibranch is often found living in sand and gravel bottoms from 20-30 meters deep. Commercial trawlers fishing at 70-100 m depth frequently get specimens aboard which tend to arrive without any cerata, as they are very easily autotomized. After the cerata detach from the animal they tend to continue moving alone; this led to the belief that those loose cerata were considered as an independent animal species (flatworms, worms, parasites) and described as such, eg under the generic name Phaenicurus.

In 1844 Forbes wrote in his report “On Aegean Invertebrata”: “The characteristic Nudibranc of the Mediterranean, a giant among its tribe, Tethys leporina, was only met with once, swimming foot up on the surface of the sea in the Gulf of Smyrna, in an exhausted state, its sides being infested by that extraordinary parasite the Vertumnus tethydicola.”

This is a carnivorous and voracious nudibranch, which usually captures its preys by projecting its immense cephalic veil over them; thus it is able to capture and feed on amphipods, isopods, small decapods, echinoderms, worms, other molluscs and even small fish. This is a species that has a good swimming ability by body contouring movements, by using its cephalic veil and even using the membranes of the rhinophoric sheaths. Schmekel & Portmann (1982) state that the spawn is a long strip with egg capsules containing several pink eggs of about 89 microns in diameter.


  • Tethys (also Tetis). In Greek mythology is the goddess of Creation, goddess of the Sea. Mother of all Gods and all creatures. (Robert Graves, Los mitos griegos. Alianza editorial. Madrid. 1985).
  • Fimbria. From Latin homonymous word fimbrĭa: extremity, the last part or the end of something. Lower edge of a dress or mantle. Strip or ornament in a dress.

This species is distributed from Iberian Atlantic shores down to the Gulf of Guinea and also in the Mediterranean Sea. In the Iberian Peninsula it has been observed in the Cantabrian shores, the coast of Portugal, Atlantic coast of Andalusia and around the Mediterranean, including the Balearic islands. It is also cited in the Canaries islands. In Catalonia it is known from the commercial trawler fishing grounds located off Tossa de Mar, Lloret and Blanes. Also found in shallow water in Badalona.

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

References for the species: Tethys fimbria

    Cantabria: Ávila Escartín (1993). Portugal: Nobre (1932, as T. leporina), García-Gómez et al. (1991, as T. cf. fimbria). Andalucía (Atl.): Templado et al. (1993b). Andalucía (Med.): Luque (1983, 1986, as Fimbria), Sánchez Tocino, Ocaña and García (2000a). Levante: Templado, Talavera and Murillo (1983), Ballesteros (1985) (both as Fimbria). Catalunya: Pruvot (1897, 1901), J. Maluquer (1907), M. Maluquer (1906-1909), Ros (1975, 1978, citada como Fimbria), Ávila (1993), Domènech et al. (2006), M@re Nostrum [Badalona 7/2003]. Baleares: Hidalgo (1916), Templado (1982a, as Fimbria), Wirtz and Debelius (2003). Canarias: McAndrew (1852, as Fimbria), Ortea et al. (2001), Moro et al. (2003).

    General: Boone, 1933:206; Cattaneo-Vietti, Chemello, & Giannuzzi- Savelli, 1990:133[P]; ICZN, 1954:242; Loven, 1842:363; Nordsieck, 1972:68; Riedl, 1983:323; Schmekel & Portmann, 1982:156[P]; Tchang Si, 1931a:108; Thompson, 1976a:[P]; Vayssiere, 1901a:82; 1913a:260; Vicente, 1967:155

    Sources: Cervera et al., 2004, Ballesteros, 2007 & 2016, McDonald, 2006 and other sources.


    Western Mediterranean:1 out of 5 stars
    Eastern Mediterranean:0 out of 5 stars
    Atlantic Ocean:0 out of 5 stars

This chart displays the monthly observation probability for Tethys fimbria based on our own records.


Tethys fimbra swimming by Piero Mescalchin

More pictures


Further reading

Cite this article as:

Ballesteros, Manuel, Enric Madrenas, Miquel Pontes (2012-2020) "Tethys fimbria" in OPK-Opistobranquis, Published: 17/05/2012, Accessed: 16/02/2020 at (https://opistobranquis.info/en/LQRxS)

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