Photos of Cuthona gymnota

March 20, 2001
From: Bernard Picton

Hi Bill,
Concerning my message about Cuthona sp. 5. Here are two pictures of Cuthona gymnota.

In C. gymnota the rhinophores and oral tentacles don't have white surface pigment and are colourless or tinged with orange. The rhinophore and oral tentacle pigmenation in these species is usually a reliable character in my experience. I still use Catriona for this species as it seems different to the other British species of Cuthona in a number of ways and has a distinctive radula.

UPPER: Skomer Is., S. Wales. - June 1976
LOWER: Streymoy, Faeroe Is. - July 1980 - more brightly pigmented than normal for the British Isles.


Picton, B., 2001 (Mar 20) Photos of Cuthona gymnota. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Thanks Bernard,
These small aeolids seem to cause problems with identification worldwide. I suspect part of the problem is the subleties and complexities of their colour patterns, which are difficult to describe in words. Hopefully the more colour photos we can publish, the greater the chance of clarifiying the differences.

Concerning Catriona, I agree that we probably have not heard the final word on the genera in this group. Unfortunately we had got to the point where every slight difference was being elevated to generic status which didn't help either. In my experience, the C. gymnota - type radula, in which the central cusp is set back from the other cusps, seems to occur amongst species which seem to be feeding on the hydroid tisue in the 'roots' or stolons of the hydroid colony rather than the polyps. I haven't any rigorous experimental evidence to support that, but some cuthonids seem to be found nestling in the basal parts of the colonies rather than up near the polyps. Have you noticed any such difference?
best wishes,
Bill Rudman

Rudman, W.B., 2001 (Mar 20). Comment on Photos of Cuthona gymnota by Bernard Picton. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from


Cuthona gymnota

Related messages

  1. Re: Cuthona gymnota? from Cork, Ireland
    From: Marina Ossokine, June 20, 2006
  2. Cuthona gymnota? from Cork, Ireland
    From: Jamie Malone, June 16, 2006
  3. Cuthona gymnota from Maine, USA
    From: Alan Shepard, September 2, 2003
  4. Re: Photos of Cuthona gymnota
    From: Bernard Picton, March 23, 2001
  5. Cuthona gymnota from the Netherlands
    From: Peter H. van Bragt , September 26, 2000

Show factsheet and all related messages