( Thuridilla hopei )

/ / Marine Inverts


Thuridilla hopei is a slender, smooth-bodied sea slug that can reach a maximum length of approximately 25mm (1). It possesses a well-developed parapodial, which is almost the length of the body; the head has a pair of enrolled rhinophores which taper towards the tip (2). As with other members of the Family elysiidae, T. hopei has no shell; the ventral surface has a transversal groove towards the head.

T. hopei has brilliant colours, the base colouration is black to royal blue or violet; the edging of the parapodia is a constant orange (2). The rhinophores are adorned with golden yellow bands, sometimes with blue borders.


T. hopei possess an acid secretion used for defensive purposes. The sea slug can also use its parapodia to swim (1).


A bottom-dwelling species found in shallow waters, usually on rocky substrate (2; 3) to depths of 25m (1).


T. hopei is endemic to the Mediterranean (2; 3).


T. hopei is herbivorous, feeding mainly on algae (2); Cladophora vagabunda in particular is often ingested with the animal then retaining the functional chloroplasts (4).

Conservation Status

Not listed under the IUCN Redlist (5).


Description written by Ben Harvey (2009)

(1)   Vérany, J. B. 1847. Aggiunta al catalogo de’ pesci della Liguria. Atti ottava riunione degli Scienziati italiani, Genova, 1846: pp. 492-494.

(2)   Hayward, P., Nelson-Smith, T. & Shields, C., 1996. Collins Pocket Guide – Sea Shore of Britain and Europe. London: Harper Collins Publisher Ltd.

(3)   Gofas, S. (2009). Thuridilla hopei (Vérany, 1853). In: Bouchet, P.; Gofas, S.; Rosenberg, G. World Marine Mollusca database. Accessed through the European Register of Marine Species at http://www.marbef.org/data/aphia.php?p=taxdetails&id=139687 on 2009-08-24

(4)   Marín, A., Ros, J. 1989. The chloroplast-animal association in four Iberian Sacoglossan Opisthobranchs: Elysia timida, Elysia translucens, Thuridilla hopei and Bosellia mimetic. Sci. Mar. 53(2-3): 429-440.

(5)   IUCN 2009. IUCN Red List of Threatened Species. Version 2009.1. <www.iucnredlist.org>. Downloaded on 24 August 2009.