Solid Black Nudibranch

April 11, 2001
From: Nathan Paden

Last night I discovered a black nudibranch in my reef tank. It very closely resembles the body type of the Risbecia tryoni nudibranch. It's rhinophores are tipped in white but the remainder of the nudibranch is solid black. I reviewed your site extensively looking for possibliities and the Dendrodoris nigra and Dendrodoris fumata do not appear to be viable candidates. Their body shape is not right and my nudibranch does not have a flowing mantle at all.

My nudibranch must be finding something to eat as the last live rock addition to my tank was some Vanasi rock several months ago. Other additions could be Fiji rock over a year ago. I do have several species of sponges that could possibly be a food source for the nudibranch. The size of the nudibranch was approx. 5 cm long and 1.5 cm wide. At first I thought it was a large suction cup that had somehow been melted into a funny shape or something! :-)
I tried to get a picture of it, however it was in the back corner of the tank and I couldn't get my camera to focus on it. I will continue to try to get a photo of it.
I would appreciate any thoughts on this. I am fairly confident in the body shape similarity with the Risbecia tryoni especially the shape of the head and the lack of a flowing mantle as shown in the Dendrodoris sp.

Paden, N., 2001 (Apr 11) Solid Black Nudibranch . [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Nathan,
Tha white-tipped rhinophores sound like Dendrodoris nigra but you don't mention anything about gills which makes me wonder if you have a nudibranch at all. If you have, it is extremely lucky, having arrived in your aquarium either with some live rock that had the right sponge food living on it, or it has found the right sponge already living in your aquarium.

The other possibility is that you have a 'slug-like' snail such as Scutus which travels well on 'live rock', is black, and feeds on algae. One easy way to tell is to gently poke its back and see if it has a white shell which is usually hidden underneath black skin flaps. Have a look at the Scutus page for some photos. The other thing ito look for are the position of the 'rhinophores'? Are they under the mantle skirt or do they emerge from pockets on the back?

Basically its hard to be sure what you have without an illustration. If it won't cooperate for a photo, could you manage a rough drawing or two which you could scan and send me?
Best wishes,
Bill Rudman

Rudman, W.B., 2001 (Apr 11). Comment on Solid Black Nudibranch by Nathan Paden. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from


Dendrodoris nigra

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