Elysia ornata

Elysia ornata (Swainson, 1840)

Elysia ornata by Sonja Ooms
Taxonomy
Class: Gastropoda  Cuvier, 1797
Subclass: Heterobranchia  J.E. Gray, 1840
Clade: Euthyneura  Spengel, 1881
Clade: Panpulmonata  Jörger et al., 2010
Clade: Sacoglossa  von Ihering, 1876
Subclade: Plakobranchacea  Jensen, 1996
Superfamily: Plakobranchoidea  J.E. Gray, 1840
Family: Plakobranchidae  J.E. Gray, 1840
Genus: Elysia  Risso, 1818
Species: Elysia ornata (Swainson, 1840) [Thallepus]

Taxonomic note. The paper by Jensen, K. (2015) proposes the synonymy of Elysia grandifolia with this species based on anatomical traits: “The finely denticulate teeth may indicate that E. grandifolia (Kelaart, 1858) should also be included in the synonymy”.

Synonyms

  • Elysia marginata (Pease, 1871)
  • Pterogasteron marginatus Pease, 1871
  • Pterogasteron ornatum Pease, 1860
  • Thallepus ornatus Swainson, 1840 (original)
  • Elysia grandifolia Kelaart, 1858

Description
This sacoglossan has an average size of 20 to 50 mm (maximum reported size is 70mm) and has an elongated body. Body colour is basically green (there are specimens with different shades of green or even brown) with numerous black spots of different sizes scattered along the whole body surface. There are also white spots combined with the black, apparently more frequent in juveniles than in mature specimens. Some specimens in the Caribbean have been observed with brown spots. The foot widens into two large lateral lobes (parapodia) which cover the dorsal surface and have the appearance of leaves with wavy edges. The parapodia have an orange or yellow submarginal band with a black line along the edges. The head is relative small and distinct from the rest of the body. There are two smooth auriculate rhinophores with the tips coloured as the parapodia. Rudimentary eyes are located right behind the rhinophores. The pericardium hump is short and narrow with the posterior part colored in white with some black spots. One pair of branching vessels enter the pericardium posteriorly and one or two more along each side of the pericardium, only noticeable if the animal has the parapodia opened. There is a groove in the right side of the body, at the attachment of the parapodia of that side to the neck of the animal, that holds the anus and genitalia openings. That groove continues across the foot sole to the left parapodium. The posterior part of the foot sole is not distinctly demarcated and the tail is rounded.

Biology
Elysia ornata lives in shallow waters, on rocky bottoms colonized by the green algae from which it feeds (Caulerpa, Halimeda, Codium and Bryopsis), and sandy areas with seagrass beds. It can be observed down to the 15 m deep. The spawn consists on a long, irregularly coiled string containing many capsules with several oocytes, usually with white extracapsular material on the external surface. The Atlantic species look very much like Singaporean specimens (Jensen, 2009; Jensen, 2015) and their egg mass has white streaks of extra-capsular material, so they are classified as the same species, which is assumed to have circum-tropical distribution (Jensen, 1992). However, there is a complex of cryptic species with a marginal orange band in the Indo-Pacific, indicated by molecular studies (Krug et al., 2013) but they look different to the Atlantic species. The large body size appears to be common in specimens that are found alone and not given the opportunity to reproduce. Repeated spawning usually cause shrinking in body size though feeding continues during the spawning period, and variation in body size of mature specimens may be caused by differences in reproductive state.

Etymology

  • Elysia. It is a name of Latin origin, derived from the word Elysium, which in mythology is the home of the blessed, known as the “Elysian fields”. The name Elysia also means “God’s oath” in Hebrew. Frieder Sauer comments that Elysia means heavenly.
  • Ornata. From Latin “ornatus”, means distinguished, honored, well equipped/endowed, richly adorned, ornate.

Distribution
Alien species for the Mediterranean, where it has been reported in Turkey, Israel and Lebanon. Present both in the Eastern and Western Atlantic, where it has been cited in Colombia, Costa Rica, Cuba, Gulf of Mexico, Jamaica, Lesser Antilles, Brazil and also in Azores, Madeira and the Canary islands. All Indo-Pacific species currently termed “ornata” probably are a complex of cryptic species in the Elysia marginata complex (see Krug et al., 2013), but samples from Singapore seem to be like the Atlantic specimens (Jensen, 2015) so they are classified as E.ornata.

Known georeferenced records of the species: Elysia ornata (z-200).
Sources:
: OBIS : OPK
: GROC 2010-2011 : VIMAR
: Enric Madrenas : Manuel Ballesteros.
: João Pedro Silva : M@re Nostrum
: Bernard Picton : Other sources
: GBIF.ORG : Marine Regions

Abundance

        Western Mediterranean:0 Stars
        Eastern Mediterranean:1 Stars
        Atlantic Ocean:2 Stars
This chart displays the observation probability for Elysia ornata
based on our own records.

More pictures

Bibliography

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:

Pontes, Miquel, Manuel Ballesteros, Enric Madrenas et al. (2012-2017) "Elysia ornata" in OPK-Opistobranquis, Published: 25/10/2014, Accessed: 22/09/2017 at (http://opistobranquis.info/en/045iz)

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