Ercolania viridis

Ercolania viridis (A. Costa, 1866)

Ercolania viridis @ Croatia by Pero Ugarković

Taxonomic Note: Ercolania funerea has traditionally been considered a synonym for this species, but its name has often been used in preference to Ercolania viridis to avoid possible confusion with Placida viridis and Stiliger viridis.

Synonyms

• Embletonia funerea A. Costa, 1867
• Embletonia nigrovittata A. Costa, 1866
• Embletonia viridis A. Costa, 1866 (original)
• Ercolania funerea (A. Costa, 1867)
• Ercolania pancerii Trinchese, 1872 
• Ercolania siottii Trinchese, 1872
• Ercolania uziellii Trinchese, 1872 

Description
Body of a maximum reported length of 16mm. Juvenile specimens (1 to 5 mm) are lighter in color, and show green lines near the eyes that go towards the cerata on the back. The adult specimens are dark green or almost black in color due to the internal digestive gland, more or less masked by the dark pigment of the skin, for this reason they were described as a different species E. funerea. The back is covered by a white band (barely visible in certain specimens) that goes from the pericardic zone to the tail. The rhinophores have a round section, are smooth and very elongated. At the base of the rhinophores, towards the outside, there are white spots surrounding the eyes, from these spots there are lines that run along the outer back of the rhinophores to their tip, which is white. Cerata are fusiform shaped and of variable size, arranged on both sides of the body and of the same coloration due to the presence of the digestive gland inside, but with a slight reddish glow and a dark red apex. Body, cerata and rhinophores are covered with numerous brownish-red spots and white spots. The anus ends in a short papilla located in the dorsal midline, above the pericardium. The male and female gonopores are under the right rhinophore. The foot is lighter in color than the rest of the body, sometimes with yellowish tones. The foot is slightly flared at the front and has rounded edges while, at the back, it ends in a pointed tail without cerata.

Biology
This species is found in intertidal pools, calm shallow water areas, and in coastal lagoons. It feeds on cladophoric algae such as Chaetomorpha aerea and C. linum, which is why it appears in bundles of algae collected for study. The egg spawn has the shape of a wide, rounded ribbon wound onto itself (with one or one and a half whorls) and contains white or yellowish eggs with a diameter of between 75-90 microns, arranged transversely. Veliger swimming larvae hatch after 7 days at 16ºC under laboratory conditions. When disturbed, it expels a white defensive liquid, thanks to the numerous glands distributed by the cerata. E. viridis is known to retain functional chloroplasts, obtained from its food, for 12-24 hours. This species can live for quite a long time in captivity, if care is taken to renew the water from time to time.

Etymology

• Ercolania. Probably dedicated to Giovanni Batista Ercolani, Italian physicyst and founder of the veterinary sciences in his country.
• Viridis. From Latín “viridis”, green.

Distribution
Due to its small size and its ability to go unnoticed, there are few reports in the literature. In the Mediterranean there is evidence of its presence in Spain (Gibraltar, Eastern Andalusia, Levante and Catalonia), France (Étang de Thau, Gulf of Marseille), Italy (Livorno, Naples and Salento), Malta (Qajjenza, St. George’s Bay and Birzebbugia), Tunisia (Lac de Tunis) and in Croatia (Split). Also reported in the coast of Ukraine, on the Black Sea. In the eastern Atlantic it has been reported in the Arcachon Bay (France) (Cuénot, 1927), in Madeira (Ortea & Moro, 1998) and in Cape Verde (Rolán, 2005), while in the western Atlantic there are reports from North Carolina (USA) to Brazil, as well as in some Caribbean islands. Reports far from the type locality may correspond to the same species, or to a different cryptic species.

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Bibliography

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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

• Biodiversity Heritage Library
• El Litoral de Granada
• Flickr pictures
• Interim Register of Marine and Nonmarine Genera
• NCBI GenBank
• OBIS - Search by Taxon
• Salento Sommerso
• SeaSlug Forum
• World Register of Marine Species

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