Phylliroe atlantica from the Azores

February 13, 2002
From: Peter Wirtz

Dear Bill,
I just looked at the Phylliroe page and this inspired me to send you the other species in the genus, P. atlantica. The animal was caught by Joao Goncalves in the channel between Sao Jorge and Pico Islands, Azores, and brought to the Department of Oceanography and Fishery in Horta, Faial Island, where I photographed it.


Wirtz, P., 2002 (Feb 13) Phylliroe atlantica from the Azores. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Thanks Peter,
These pelagic nudibranchs are indeed fascinating animals. I am not an expert on them but Odhner (1936) considered that Phylliroe lichtensteini (Eschscholtz, 1825) was an older name for Phylliroe atlantica Bergh, 1871. Have I missed a later review?

The other point is the differences between the two accepted species in the genus, Phylliroe lichtensteini and Phylliroe bucephala. From my reading of the literature it seems the only real difference is that P. lichtensteini is said to have 3 ovotestis lobes and P. bucephala has only two. It seems to me that too few animals have been looked at for us to confidently accept that the number of lobes is not an intraspecific variable. Be that as it may, I am not sure how many ovotestis lobes are present in your animal. I have posted a labelled copy of your photo alongside. There would appear to be two partially joined lobes at the bottom. There is also a similarly coloured structure directly above. I am not sure if that is another lobe lying over the top of the intestine, or whether it is a swelling in the intestine. If we interpret it as an intestinal swelling it makes your species P. bucephala, if we interpret it as another ovotestis lobe, then it makes your species P. lichtensteini.

Perhaps you have another photo which shows this object more clearly. Either way it seems this genus needs a bit more study. Any comments welcome.

• Odhner, N. H. 1936. Nudibranchia Dendronotacea -- A revision of the system. Memoires du Musee Royal d'Histoire Naturelle de Belgique, series 2, fasc. 3: pp. 1057-1128, pl. 1.
• Pruvot-Fol, A. 1946. Revision de la famille des Phylliroidae (Phyllirhoidae)Bergh. Bulletin du Museum National d'Histoire Naturelle, Paris, series 2, 18(2): 172-178.
• Ralph, P. M. 1959. Notes on an abnormality in the liver caeca of the nudibranch Phylliroe lichtensteini Eschscholtz, 1825. Proceedings of the Malacological Society of London, 33: 186-192.

Best wishes,
Bill Rudman

Rudman, W.B., 2002 (Feb 13). Comment on Phylliroe atlantica from the Azores by Peter Wirtz. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from