Eubranchus yolandae from the tropical eastern Pacific

August 8, 2007
From: Ali Hermosillo

Dear Bill,

Last but not least, here is Eubranchus yolandae.

When Angel and I were working on this paper, the SEM had some problems and we could not get the image of the radula of this species, which we were almost sure was a Cuthona since it had all the external and reproductive characteristics of this genus.

What would be our surprise when the SEM finally came out and we saw the radula had a rachidian and laterals. For those of you who are not familiar with what that means here is a little explanation. The great majority of aeolids have a radula ribbon with only a central rachidian tooth, meaning one tooth per row. Very few genera (Flabellina and Eubranchus included) retain one small lateral on each side.

Locality: Los Arcos, Bahía de Banderas, 52 feet, Jalisco, Mexico, tropical eastern Pacific, 26 May 2004, Rocky subtidal. Length: 7 mm. Photographer: Ali Hermosillo.

Though small and hard to find, even at night, this species does not seem to be rare, you just have to find the eggs first.


Hermosillo, A., 2007 (Aug 8) Eubranchus yolandae from the tropical eastern Pacific. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Ali,
Thanks for the nice photos and background information on these species. This is another brightly coloured species.

I have a couple little points about your description. You describe the anal opening as acleioproctic, which is the usual position in Eubranchus, outside the ceratal clusters - above them in fact.  From your photos I would think the anus is in the white patch I have ringed, rather than 'at the same level of the lower cerata' as described in your paper, which is a cleioproct position.

The second point is I think the pattern of "fine opaque yellow lines .. along the dorsum" which you describe, are the fine digestive gland ducts which run between the ceratal groups.

Best wishes,
Bill Rudman

Rudman, W.B., 2007 (Aug 8). Comment on Eubranchus yolandae from the tropical eastern Pacific by Ali Hermosillo. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from