Dorsal/ventral swimming in nudibranchs

December 11, 2003
From: Paul Katz

Does anyone know if there are any nudibranchs besides Tritonia species that swim with dorsal/ventral body flexions? Many species swim with lateral body flexions. The description of swimming by Plocamopherus ceylonicus sounds like it might be a dorsal/ventral swimmer because it flattens in the doral/ventral axis. Can someone comment on that? The Notaspid, Pleurobranchaea californica also swims dorsal/ventrally. Are there others?

Also, does anyone know of any other interesting swimming movements in nudibranchs that differ from just lateral flexions. Certainly, Hexabranchus sanguineus seems to have undulations that are more complex than lateral flexions. Could they be a combination of lateral and dorsal/ventral flexions? Also Bornella anguilla has "eel-like" movements that could be more complex than simple lateral flexions.
Paul Katz.

Katz, P., 2003 (Dec 11) Dorsal/ventral swimming in nudibranchs. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Paul,
There is quite a literature on the topic so I have prepared a Fact Sheet and bibliography which should get you into the topic. I guess Rule 1 is that there is no general rule. Some tritoniids exhibit dorso-ventral flexion, but there are others which show lateral flexion. The eel-like flexion of Bornella anguilla seems to be a development of the simple lateral flexion found in other species of the genus.

If you move outside the nudibranchs there are many wonderful adaptations for swimming that have evolved. Are you planning to do some research in the area?

Best wishes
Bill Rudman

NOTE: If there is anyone who would like to prepare a review on swimming for the Forum? It would be very welcome. Contact me for some guidelines.

Rudman, W.B., 2003 (Dec 11). Comment on Dorsal/ventral swimming in nudibranchs by Paul Katz. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from