Archidoris pseudoargus
(Rapp, 1827)

Suborder: DORIDINA
Family: Dorididae


European coast from Norway to Spain, and the Mediterranean. from intertidal to 300m.


UPPER: NE Soay, St. Kilda, Scotland - 22 Aug 1985 - 6cm. LOWER: Ruecallan, Rathlin Is., N. Ireland - Jun 1988. Photos: Bernard Picton

Large dorid reaching over 120mm in length. Common in the British Isles where it is known as the Sea Lemon. Mantle covered in blunt tubercles, and has a mottled colour pattern of brown, pink, green, yellow and white blotches. Feeds on siliceous sponges including Halichondria panicea and Hymeniacidon perleve. In much of Europe it is identified as Archidoris tuberculata Muller, 1778.

Archidoris pseudoargus is often confused with another large dorid Geitodoris planata. As discussed below by a number of participants, there are distinguishing features. Unfortunately they are more apparent in the field than in photos. Geitodoris planata can be distinguished from Archidoris pseudoargus by the light coloured stellate patterns on the mantle (acid glands), and also by the more flattened shape. The underside of the animal is also important with Geitodoris planata having brown spots on the mantle, and conspicous oral tentacles, both characters lacking in Archidoris pseudoargus. In living animals there is a difference in texture, Geitodoris being crisper, harder and flatter.

• Thompson, T.E. & Brown, G.H. (1984) Biology of Opisthobranch Molluscs, Vol 2. Ray Society: London.

Authorship details
Rudman, W.B., 2001 (June 12) Archidoris pseudoargus (Rapp, 1827). [In] Sea Slug Forum. Australian Museum, Sydney. Available from

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