Possible autotomy in Jorunna from Colombia

September 25, 2001
From: Elianny Dominguez

Dear Bill,
It is my wish to be able to work with the internal anatomy of this animals some day (and I do hope you can give me that background information on the subject); I'm familiar with the importance of the description of the radula, as an essential part of the work of identifying nudibranchs species. Unfortunately, for our thesis we didn't have the means (equipment or guidance support) to include the internal anatomy of the animals we would collect in the field trips; specially the smallest ones, like the aeolid with the orange lateral lines I sent you before, which are the hardest to ID.

But hopefully, since quite a few of our animals have turned out to be new for Colombia, our thesis could convince our Deacon to support the continuation of our work by other students who could include studies of the internal biology of opistobranchs. This is why we are trying very hard to ID this animals only through external descriptions. And it is also why we're very very grateful to you and others who have been lending us a hand.

I've read about autotomy in some nudibranchs, and the chapter about this mean of defence on the Forum. Recently we found this animal which has an unusual slender body in the mid transversal portion. I don't know if this could be autotomy or if they are some species of nudibranchs with this particular characteristic. As you can see, part of the mantle skirt is "missing" on both sides of the animal.

We found it on rocky substratum (Santa Marta, Caribbean coast of Colombia), under a rock at 15 cm of depth. The animal is about 1cm long, the color is opaque white with a few dark brown spots; and the dorsal surface is not smooth but full of thin papillae. You can see on one of the pictures the shape of the rinophores and the gills; we couldn't tell if the gills where that short or if they were retracted.

Thank you for everything and kind regards,
Elianny Dominguez.


Dominguez, E. , 2001 (Sep 25) Possible autotomy in Jorunna from Colombia. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/5305

Dear Elianny,
I sympathise with your problems. It is indeed difficult without guidance and decent equipment. You can do some basic stuff with simple equipment so I will try and get some information organised on radula extraction for you.

This animal looks as though it is a species of Jorunna, a genus which is characterised by the dense covering of spiculate paillae (caryophylldia) covering the mantle. If your photo was from Europe is would suggest it is Jorunna tomentosa but I don't think it has been reported fron the western Atlantic. As far as I know the only Jorunna reported from the western Atlantic is Jorunna spazzola (Marcus 1955) from Brazil.

Concerning autotomy. Yes species of Jorunna commonly break off parts of their mantle, another reason to think this is a Jorunna.

• Marcus, Er (1955) Opisthobranchia from Brazil. Boletim da Faculdade de Filosofia, Ciencias e Letras. Universidade de Sao Paulo, Zoologia, 20: 89-261. (Pls. 1-30)
• Marcus, Ev (1976) On Kentrodoris and Jorunna (Gastropoda Opisthobranchia). Boletim de Zoologia, Universidade de Sao Paulo, 1: 11-68.

Best wishes,
Bill Rudman.

Rudman, W.B., 2001 (Sep 25). Comment on Possible autotomy in Jorunna from Colombia by Elianny Dominguez . [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/5305