Re: Chromodoris krohni

January 24, 2001
From: Angel Valdes

Dear Bill,
I took a look at Alma's photos and I do not have any doubt that they are of specimens of Chromodoris krohni (Vérany, 1846). It is fairly common from northern Spain to North Africa and the Mediterranean Sea. It is clearly distinguishable from other chromodorid species from the eastern Atlantic by the presence of three yellow lines on a pale blue background. The lines run from the gill area to the rhinophores, the two most external joining right behind the gill. In the adult specimens (upper and lower right photos)there are also small yellow dots next to the lines. In the juvenile specimens the lines are pale yellow or even white (lower left photo). Other eastern Atlantic species with yellow of white lines have a dark blue dorsal color and they belong to the genus Hypselodoris (H. tricolor, H. villafranca, H. bilineata, H. cantabrica, H. malacitana, H. picta, H. fontandraui and H. orsini. They are easily distinguishable from C. krohni by the narrower mantle margin and absence of mantle glands in large areas of the mantle edge. A probably related species to C. krohni is Chromodoris purpurea (Risso in Guérin, 1831), which is very similar but lacks yellow lines (I enclose a photo taken in northern Spain). Because of the pale blue background color this species was not included in the monograph by Ortea et al. (1996) dealing with the dark blue Atlantic chromodorids.

• Jesús Ortea, Ángel Valdés and José Carlos García-Gómez, (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. Revista de Ecologia y Oceanologia y Biodiversidad Tropical. Supplement 1. 165pp.

All the best,

Valdes, A., 2001 (Jan 24) Re: Chromodoris krohni. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Thanks Angel,
I have separated your photo of Chromodoris purpurea on to a separate page. The blue chromodorids of the Mediterranean and the Atlantic are indeed a fascinating group.
Bill Rudman

Rudman, W.B., 2001 (Jan 24). Comment on Re: Chromodoris krohni by Angel Valdes. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from


Chromodoris krohni

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