Martín-Hervás M.R., Carmona L., Malaquias M.A.E., Krug P.J., Cervera J.L.

A new sacoglossan species, belonging to the genus Elysia Risso, 1818 is described from Faial Island (Archipelago of the Azores, Atlantic Ocean). This new species is easily recognizable by its bright and translucent orange colour, visible digestive gland through the skin, and presence of opaque white rounded papillae along the edge of the parapodia. The external morphology of this species resembles the Atlantic E. flava Verrill, 1901 and the Indo-West Pacific species E. obtusa Baba, 1938, but the colouration depicts subtle differences. The two aforementioned species have an overall translucent pale-yellow body colour with a greenish inner surface and white spots on the tips of the rhinophores, while the new species is orangish with uniform orange rhinophores. In addition, E. flava and E. obtusa have a broader bright white line on the margins of the parapodia formed by white papillae, which may also be found in small clusters on the pericardial swelling. In some cases, white patches appear scattered on the outer side of the parapodia, not visible in the species here described. Finally, COI uncorrected p-distances clearly distinguish this species from all closely related Elysia species, with a minimum distance of 10.6 %.