Nudibranchs cleaning scorpionfish?

May 4, 2002
From: Michael O'Neill

To all,
Recently in the Poor Knights, New Zealand, I photographed two species of nudis (Ceratosoma amoena and Aphelodoris luctuosa) crawling on a Scorpionfish (Scorpaena cardinalis).

Are the nudis feeding on the mucus of the fish?
Are the nudis cleaning the fish, the same way a reef fish might?
Are the nudis just plain "lost"?

Any feedback is greatly appreciated.
Best regards,
Michael Patrick O'Neill

O'Neill, M.P., 2002 (May 4) Nudibranchs cleaning scorpionfish?. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Michael,
I think they are just plain lost. Both are sponge feeders. Mind you nothing is too strange for molluscs. There are species of colubrariid and marginellid snails which wait for Parrot Fish to form their 'nests' to sleep in at night and then feed on them by piercing soft parts like around the eyes. I think there are also cancellarid snails which do similar things to rays. And of course there is always Gymnodoris nigricolor which lives on gobies.

So although I think they are lost, it always pays to keep an open mind about such things.
Best wishes,
Bill Rudman

Rudman, W.B., 2002 (May 4). Comment on Nudibranchs cleaning scorpionfish? by Michael O'Neill. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from



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