Relationship between nudibranchs & corals

March 2, 2001
From: Joanne

I'm a student at the University of California, Santa Cruz, and am currently taking an ocean science class. I have to do a presentation as a final project for my class. My topic that I have chosen is the relationship between nudibranchs and corals. My main question is, is this relationship symbiotic, commensal, or parasitic? And I know that only some species are able to have this kinda of relationship, which species are they? Also the information I found about this topic is highly limited, it would be greatly appreciated if you can provide some info or possible links.

Thank you very much,

Joanne, 2001 (Mar 2) Relationship between nudibranchs & corals. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Joanne,
There is a lot of information on coral-feeding nudibranchs in the Forum. As a general rule, if you are looking for information on the Forum use the SEARCH button. If you type coral, for example, you will get a list of relevant pages to go to. Your best bet would be to got to the Coral Feeding Index Page.

Are these animals parasites, commensals etc etc? It is all a question of definition. Is a large mammalian herbivore which only eats certain plants a parasite, a symbiont or commensal - or is it just a grazing herbivore? I remember Russell-Hunter in one of his books questioning why an enormous lion, feeding on prey much smaller than itself was considered 'noble and brave' while a flea or tick, living a perilous life feeding on an animal much larger than itself, was despised by us, its very name being used as a term of abuse.

I think it is more important to understand an animal's relationship to the other organisms they are associated with, rather than find them a label. Most of the nudibranch coral-feeders have a very close obligate relationship with a particular species of coral, and often they have modified their shape and colour to enable them to hide on their coral food, which becomes their home as well as their food. At the same time some of these nudibranchs have evolved a close relationship with the coral's symbiotic zooxanthellae, removing them from the coral and keeping them alive in their own tissues.

Read the information in the Forum on these fascinating animals and see how they fit the definitions you have for commensals, parasites etc.
Best wishes,
Bill Rudman

Rudman, W.B., 2001 (Mar 2). Comment on Relationship between nudibranchs & corals by Joanne. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Related messages

  1. Coral - feeding ? aeolid
    From: Charles Raabe, July 29, 2006
  2. Sea slugs and coral?
    From: Melissa H, October 7, 1999
  3. Pinufius rebus and coral-feeding
    From: Bill Rudman, October 7, 1999

Show factsheet and all related messages