Elysia viridis

Elysia viridis (Montagu, 1804)

Elysia viridis @ Laguna Fusaro, Bacoli, Napoli by Guido Villani




































Elysia viridis  (Montagu, 1804)

 Classification according to Bouchet et al. (2017)
Taxonomic source: World Register of Marine Species (AphiaID: 139686).

  • Actaeon elegans de Quatrefages, 1844
  • Aplysiopterus neapolitanus Delle Chiaje, 1830
  • Elysia fusca Philippi, 1844
  • Elysia marmorata Cantraine, 1835
  • Elysia minuta Sars M., 1835
  • Elysia pagenstecheri Marcus Ev., 1982
  • Elysia viridis var. olivacea Jeffreys, 1869
  • Laplysia viridis Montagu, 1804 (original)

The Mediterranean specimens of this species usually measure between 10 and 15 mm in length but there are reports of specimens measuring up to 55 mm in the European Atlantic coasts (Thompson & Brown, 1984). This species has the typical morphology of the family, with a little slender body, short rhinophores and triangular parapodia. The general body coloration is dark green but it can vary according to the animal’s diet, as specimens can be coloured in different green hues, brown, reddish or even black. The body is scattered with red, pink, blue, yellow or green spots. In the animal’s dorsum there are marked veins that meet at the back of the pericardial region, quite swollen and located between the anterior base of the parapodia. The rhinophores are auriculate on its outer side, they are dark green coloured and may have a higher concentration of colored granulations near the apex, that give a light blue-violet iridescence. The edge of the parapodia usually has whitish scores, that can also be found along the sides of the body and the rhinophores. When the animal is shrunk, the edge of the parapodia may appear lobed. The eyes, large and slightly protruding, are located at the base of the rhinophores, on a circular and somewhat depigmented area. The ramifications of the digestive gland can be seen through the integument in the inner side of the parapodia, in the head and within the rhinophores. The anus is at the end of an anal papilla located below the right rhinophore. The foot is narrow and has short propodial tentacles at its front end.

This species is very common and lives in a wide variety of algae on which it feeds, in chlorophyceans such as Cladophora rupestris, Codium sp., Clathrata enteromorpha, Ulva lactuca and Briopsis sp., rhodophyceans as Chondrus sp., phaeophyceans as Cystoseira sp. and it has also been reported on the seagrass Zostera sp. (Thompson, 1976; Bouchet, 1984; Schmekel, 1968), although it is suspected that possibly its food spectrum is not that wide. In the Iberian Mediterranean coasts, it is almost always found on Codium fragile, on which it feeds and lays the eggs. Like other sacoglossans, this species “hijacks” the chloroplasts of the algae on which it feeds (a phenomenon called kleptoplasty) and incorporates them into their own tissues, where they remain active and performing photosynthesis for several days. The abundance of these chloroplasts in the sacoglossan tissue is what determines the greenish tone of the specimens. When kept in aquariums with no food they progressively lose the green color, which becomes clearer to finally acquire a yellowish color. E. viridis is able to secrete a defensive mucus whose main component is a polypropionate called “elisione”, that the animals synthesize de novo, that is, it does not come from ingestion of the algae that conforms its diet (Marín & Ros, 2004). The spawn of this species, which are deposited on the algae on which the animals feed, is shaped like a flat spiral with white eggs about 70 microns in diameter (Schmekel & Portmann, 1982).


  • viridis = refers to the green colour that present most of the specimens of this species, caused by the chloroplasts of the algae they eat and that are accumulated in their tissues.

Elysia viridis has a wide geographical distribution and it has been reported in all European coasts both Atlantic and Mediterranean, the Atlantic coast of Morocco, Canary Islands, Madeira, Azores and even in the Baltic Sea. In the Iberian Peninsula it has been collected in all coastal areas, while in Catalunya it has been reported in many locations of the Costa Brava, Maresme and in Cubelles. According to Bouchet (1984), it is possible that many reports for this species are related to E. translucens, morphologically very similar to E. viridis.

Known georeferenced records of the species: Elysia viridis
: 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 Elysia viridis based on our own records.



More pictures


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Further reading

Cite this article as:

Ballesteros, M., Madrenas, E. & Pontes, M. (2023) "Elysia viridis" in OPK-Opistobranquis. Published: 14/05/2012. Accessed: 05/12/2023. Available at (https://opistobranquis.info/en/?p=264)

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