Hypselodoris bilineata from Senegal

Dear Marina & Patrice
This is another of the confusing 'blue chromodorids'. Although rather different in colour from 'typical' specimens, this is considered to be a colour form of H. bilineata. This colour form has been reported from Ghana (Edmunds, 1971) and Senegal (Bouchet, 1975; Ortea etc al., 1996). Bouchet considered the colour differences were because Pruvot-Fol's Morocan animals were juveniles, but as adults of her colour form have been reported, it seems the difference may be geographic.

The main colour differences are that in the Ghanaian / Senegalese colour form the median yellow lines are much further apart, and between them are many broken creamy yellow or white lines. The black zone, between the inner yellow line and the yellow border, is much narrower and the blue pigmentation forms a blue line around the anterior end of the mantle and a series of spots down each side. Although these colour forms look rather different, if you look at the photo in the Fact Sheet of a 'typical' colour form from southern Spain, you can see a few white streaks in the centre of the mantle between the two yellow lines, which no doubt are a link between this colour form and the forms from further south with multiple white lines.

• 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.
• 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)

Best wishes,
Bill Rudman