Predation on sea slugs

April 25, 2002
From: Alicia Hermosillo

Dear Dr. Rudman,
I was reading the posts on 'what eats sea slugs??'. I wanted to share something.

Last February, as I was surveying in Los Arcos, Bahia de Banderas, Pacific Coast of Mexico, I turned a rock and saw 3 specimens of Phidiana lascrucensis Bertsch & Ferreira, 1974 under it. As I was measuring and writing down observations, a damselfish came by and ate one of them. I thought it would spit it out like they usually do, but it did not.

I thought this was very strange, then I read in Mike Miller´s Slug Site, on Nudibranch of the Week 31. Han´s tale of finding this species for the first time, and it turns out one of his specimens was eaten by a fish as well.

Hermosillo, A. , 2002 (Apr 25) Predation on sea slugs. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Thanks Ali,
Any little bit of information is valuable. I guess most cases of predation on nudibranchs goes unnoticed. As I have said before, without hard parts, most opisthobranchs are unidentifiable in stomach contents. Fish often fish 'mouth' nudibranchs, moving them around in their mouths, sometimes spitting them out, but sometimes persisting until the nudibranch has exhausted its supply of nasty chemicals, nematocysts etc, then they eat them. Bertsch & Ferreira (1974), in their original description of this species also report that Navanax inermis ate an animal in aquarium.
Best wishes,
Bill Rudman

Rudman, W.B., 2002 (Apr 25). Comment on Predation on sea slugs by Alicia Hermosillo. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from