Acanthodoris hudsoni color variation?

Hi Pete,

To answer your question right off, all of these specimens are in fact Acanthodoris nanaimoensis. The important give-away when you see these darker pigmented, mottled specimens, is that the tips of the rhinophores and/or gills have some degree of red wine color, as shown in the close-up alongside.

As you are aware, Acanthodoris hudsoni has a white body with yellow at the tips of the dorsal papillations, rhinophores and gills. But there is never any wine colored pigmentation. Both species have a yellow marginal line.

Photographs of both color phases of A. nanaimoensis can be found in Lamb & Hanby, page 255 top, insert, and my very first edition of Pacific Coast Nudibranchs, (1980, blue cover), page 49.

Some of my colleagues have suggested that if your start with A. pilosa, and move to A. hudsoni, then to A. nanaimoensis and A. rhodoceras, we have a single species with very wide color variation, from white to dark, no color on tips to red then black. Food for thought.

• Lamb, A. & B.P. Hanby. (2005)  Marine Life of the Pacific Northwest. Harbour Publishing.
• Behrens, D.W. (1980) Pacific Coast Nudibranchs.  Sea Challengers Publishing.

Thanks for sharing these,
Dave Behrens