Hypselodoris bilineata
(Pruvot-Fol, 1953)

Order: NUDIBRANCHIA
Suborder: DORIDINA
Superfamily: EUDORIDOIDEA
Family: Chromodorididae

DISTRIBUTION

Atlantic Ids, West Africa, western Mediterranean

PHOTO

Upper Photo: El Timoncillo Reef, Bay of Algeciras (Strait of Gibraltar, southern Spain) at 17 m depth (19.8ºC), size: 25 mm long. August, 2000. Photo: Alma Sánchez.
Lower Photo: Dakar, Senegal, Eastern Atlantic, Site: Tacoma Wreck, Depth: 12m. May 26, 2003. Size: 25-30mm. Photo: Marina Poddubetskaia

The mantle is essentially black with yellow markings and lines and bright blue markings. The edge of the mantle has a thin black line then a submarginal bright yellow or creamy yellow line. Sometimes a section of a yellow line can have a path of white. In the centre of the mantle are a pair of yellow lines which run anteriorly between the rhinophores then join as a loop just in front. Posteriorly the lines run around the edge of the gill pockets and join behind it. Between these median yellow lines and the yellow border the mantle is black with large elongate patches of bright blue. The rhinophore stalk is black and the club dark blue-black with a yellow line around the base of the club and up the posterior midline. The gills are dark blue black with a single yellow line along the inner edge and a double yellow line along the edges of the broad outer rachis. The sides of the body and the foot are blue. with one or two longitudinal yellow lines which join on the postero-dorsal part of the foot. This species was described by Pruvot-Fol from Morocco, and matches Alma Sánchez's photos in the Forum from southern Spain. It grows to at least 30mm in length.

There is some variation in colour pattern in this species. In the northern part of its range the median pair of yellow lines can sometimes merge into a single line. In other animals there can be a few white streaks between the yellow lines. Further south, the yellow lines an be separated by a broad median region with many broken white lines. See message & photos below discussing this colour form with multiple white lines.

References:
• Bouchet, P. (1975) Nudibranches nouveaux des cotes du Senegal. Vie et Milieu, 25(1): 119-132
• Edmunds, M. (1981) Opisthobranchiate Mollusca from Ghana: Chromodorididae. Zoological Journal of the Linnean Society, 72(2): 175-201.
• Ortea, J., Valdés, A. & and García-Gómez, J.C. (1996) Revisión de las especies atlánticas de la familia Chromodorididae (Mollusca: Nudibranchia) de grupo cromático azul. [Review of the Atlantic species of the family Chromodorididae (Mollusca: Nudibranchia) of the blue chromatic group.] Avicennia, 1996, Suppl. 1: 1-165.
• Pruvot-Fol, A. (1953) Etude de quelques opisthobranches de la cote Atlantique du Maroc et du Senegal. Travaux de l'Institute Scientifique Cherifien, Zoologie, 5: 1-105. (Pls. 1-3)

Authorship details
Rudman, W.B., 2003 (May 4) Hypselodoris bilineata (Pruvot-Fol, 1953). [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/factsheet/hypsbili

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