Nembrotha rutilans in aquarium

September 19, 2000
From: Jeremy Rose

Note added 4 March 2008: Following Pola et al (2008) the name N. rutilans has been replaced by Nembrotha purpureolineata [see message #21419].

I came across David & Leanne's posting.

Interestingly enough I have just purchased a N. rutilans from a local marine shop here in London, UK. It was so amazing I just had to get it for my reef tank.

Because of the posting (and others) I have been able to identify the species.

Some things happened

10th September Placed in the tank
11th September Chevron Tang and Sweet Lips died (I don't know if there is any connection)
12th September it climbed up a red Gorgonia and laid a yellow tissue like ribbon. I had no idea what was happening although I thought it might be laying. Your posting clarified this. Yellow Tang had a little taster of the ribbon.
13th September both ribbon and N. rutilans are still up the Gorgonia.

Is it poisonous?
What happens to the ribbon - do little ones hatch from it? If so, how long does it take and what should I do?

Jeremy Rose

Rose, J., 2000 (Sep 19) Nembrotha rutilans in aquarium. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Jeremy,
Is your Nembrotha poisonous to your fish? Did it kill them? I'm not sure. Many nudibranchs have nasty chemicals in their skins for defence. These are usually obtained from their food, either directly or as a molecule which they can easily alter. Ascidians (sea squirts, tunicates), which species of Nembrotha eat, do have defensive chemicals, and species of Nembrotha do produce secretions from their skin. So it is possible that they could have killed you fish, but I don't know of any experimental observations to show that they can. Certainly species of Phyllidia and related genera are not good company in an aquaria, because they do produce toxic secretions.

As you say, the ribbon is an egg ribbon. Often nudibranchs when they are stressed, lay an egg-ribbon almost as though they know they might not have long to survive and should attempt to perpetuate their species. If the eggs are fertile they will produce tiny free-swimming veliger larvae, which without a lot of care will almost certainly not survive aquarium life.

The other bad news is that most nudibranchs have very specialised diets. In the case of species of Nembrotha, each species eats one, or a few, species of ascidian. Even if you could buy the specific species of ascidian, the chances of keeping it alive in your aquarium as food for your Nembrotha are very slight.

Best wishes,
Bill Rudman.

Rudman, W.B., 2000 (Sep 19). Comment on Nembrotha rutilans in aquarium by Jeremy Rose. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

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