Cyerce graeca

Cyerce graeca  Thompson, 1988

Cyerce graeca @ Punta del Romaní, L'Escala, Spain 6-02-2016 by Enric Madrenas




































Cyerce graeca  T. E. Thompson, 1988

 Classification according to Bouchet et al. (2017)
Taxonomic source: World Register of Marine Species (AphiaID: 140091).
The body is translucent white, colored by a characteristic dark brown pattern which essentially covers the entire dorsum, except the area around the eyes, head, pericardial area, the area ahead of the rhinophores and their tips, but the transparency of the rest of the body often gives the animal an uniformly colored look. The cerata are very wide and somewhat inflated, very mobile and easily autotomized if the animal is disturbed, leaving behind these organs that change shape for hours to distract the attention of predators. The animal quickly regenerates the lost cerata. Both the dorsal and ventral surfaces of the cerata are translucent white, except for a row of blunt brown digitations at the edges of the cerata that in some specimens appear as a brown line along the edge of each cerata, missing in the smaller cerata on the front of the animal. Small white scores were also observed forming a band at the tips of the cerata, corresponding to opalescent glands, most likely of defensive character. The digestive tract is dark green or almost black brown and can be seen by transparency in different parts of the body, both dorsal and ventral. All head tentacles are wound, the rhinophores bifurcated (characteristic of this family), of which the top one is colored brown but the lower one and oral tentacles are light colored. The previous propodial margin is bilabiate, and the foot has a transversal mesopodial slit. The anus is located latero-dorsally on the right side, visible as a light colored papilla, located right ahead of the pericardial prominence. The largest specimen Thompson found measured 11 mm in length.

This species bears some resemblance to the little studied Cyerce antillensis Engel, 1927, first described in Tobago, in the Caribbean, and later found in Curaçao and in Florida by Marcus & Marcus (1967, Plate 1) under the name Cyerce cristallina, Jamaica by Thompson (1977) and Bermuda by Clark (1984) and Jensen & Clark (1986). The shape of the radular teeth is similar, but there are important differences in the body color pattern in living specimens, which have wavy and soft pale brown limbs in Cyerce antillensis, compared with dark brown digitate ceratal limbs of Cyerce graeca. Marcus & Marcus (1970) attempted to set objective anatomical criteria to distinguish the two species from the Caribbean, especially stressing the importance of examining the pharynx, specifically a laminate muscular organ attached to the back of the buccal mass of the animal. This had a bulbous shape in Cyerce graeca, more like that of Cyerce antillensis than the illustrated by the same authors of Cyerce cristallina.

Like all sacoglossans, this species feeds on algae. Specimens have been found on Flabellia petiolata (Thompson, 1988) and other hard substrate algal growths (Petrusek, 2003) and (Atero, 2015) and also under stones (Pontes, 2016). This species is a extremely rare observation because of its excellent cryptic capabilities, blending it with the surrounding environment. It has been found from the surface down to 30 meters of depth.


  • Cyerce, of uncertain meaning, seems related to the Greek mythology. Classical authors like Bergh rarely explained the origins of the names they proposed, but they used to be inspired by the Greek and Roman mythology.
  • Graeca. From Latin “graecus”, Greek, from Greece.

Thompson’s original description was based on 3 specimens of about 11mm collected in Greece (Saronis, 28/07/1982; Kilini (type locality), 3/06/1986 and Lagonisi, 17/06/1986). More specimens were later found near Sumartin, Brac Island, Croatia (Adam Petrusek, 7/09/2003, Sea Slug Forum) at a depth of 25-30 meters, always on algae growing on hard substrates. There are also pictures in Internet of 5mm specimens off the coast of Antibes, France (Gilles Cavignaux, 7/05/2009, limaces of Rève) and (Paul Henri Adoardi, 1/06/2010, Photo Bio Sous-Marine) in very shallow water. Some specimens found on the island of Mallorca (Nando Darder, 04/07/2005, GROC) and (Javier Atero, 15/07/2015, Flickr) would represent the first citations for Spain, the second also found in shallow water. Two more findings, the first in the Cala Ventosa, Sant Feliu de Guixols (Xavier Salvador, 26/08/2015) in less than one meter of water and a second 20mm specimen in Punta del Romani, L’Escala (Miquel Pontes , 6/02/2016) in 12 meters of water correspond to the first reports for Catalonia and the whole Iberian Peninsula. There are two unique citations outside the Mediterranean, the first in Azores (Wirtz & debelius, 2003 – p.193) as Cyerce antillensis, although a detailed observation of the photo published suggests that it really is Cyerce graeca, because it does not fully match Cyerce antillensis description. The second report (Wirtz, 2005) corresponds to a finding in shallow water (a few cm.) in a natural pool in Porto Moniz (Madeira).

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

References for the species: Cyerce graeca

    We have not yet published references for Iberian coasts of: Cyerce graeca.


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

This chart displays the monthly observation probability for Cyerce graeca based on our own records.

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Further reading

Cite this article as:

Pontes, Miquel, Manuel Ballesteros, Enric Madrenas (2021) "Cyerce graeca" in OPK-Opistobranquis. Published: 14/09/2014. Accessed: 04/08/2021. Available at (

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