Symbiosis and commensalism

March 28, 1998

Dear sir,

In addition to learning more about the mucus on sea slugs' bodies, I would like to know about any symbiotic relationships that sea slugs share with any other organisms.
Thank you for your time,

Andrea Stephenson
Moulton, Texas,

Stephenson, A., 1998 (Mar 28) Symbiosis and commensalism. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

"Symbiosis" and "commensalism" are two of many names that have been given to pairs of organisms that live together in a close relationship. The relationship can consist of two animals, two plants, a plant and an animal, or even a fungus and an algae (such as in lichens). Many sea slugs have developed such relationships. Small crustacea called copepods are often found living on dorid nudibranchs. They have not been studied well enough to know whether each nudibranch has its own species of copepod or whether the copepods live exclusively on the nudibranchs. The copepods are easily recognised because their two large egg sacs look like a pair of large "tails". Another more spectacular example is the shrimp Periclimenes imperator which is always found living on large dorid nudibranchs such as the Spanish Dancer, Hexabranchus, or on chromodorids such as Chromodoris tinctoria.

Bob Bolland has just posted a series of photos of another remarkable association, this time between a nudibranch (Gymnodoris nigricolor and fish (gobies). It is well worth a look.

Another quite different group of relationships have been discovered with sea slugs and involves plants and plant organelles. As I have described for Elysia pilosa many sacoglossans keep chloroplasts and other plant plastids alive to obtain the sugars they produce from photosynthesis. Some nudibranchs show various degrees of ability to harness solar power by keeping whole single-celled plants (zooxanthellae) alive in their tissues for the same purpose. This is described on the page on "solar-powered nudibranchs"

Bill Rudman

Rudman, W.B., 1998 (Mar 28). Comment on Symbiosis and commensalism by . [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

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