Pectenodoris trilineata from Lembeh

March 30, 2010
From: Franco De Lorenzi

Dear prof. Rudman
these three specimens, all from Lembeh, have in common general features probably of Pectenodoris trilineata but the yellow colour line on 2 of the nudibranchs in photo give me some doubts.

Are these variations? In the first photo, it is possible to see another same nudibranch beneath the sand. I relate this in case it may help.

Locality: Lembeh strait, 16 metres, Indonesia, indopacific ocean, 22-24 august 2008, black sand. Length: 10 mm. Photographer: Franco De Lorenzi.

Thanks a lot.

Franco De Lorenzi, 2010 (Mar 30) Pectenodoris trilineata from Lembeh. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Franco,

If you look through earlier messages on this species you will see that Pectenodoris trilineata shows quite a lot of variation in the presence of yellow on the white lines. Sometimes there are really only two lines.

Your upper photo illustrates quite well how difficult it can be to find out what these animals are feeding on. The animal you describe as being buried in the sand is almost certainly burrowing and feeding on its  favourite food - a greyish-blue species of Dysidea. I suspect all the background in that photo, which looks like sand, is a layer of Dysidea over which are scattered grains of sand and shell grit. In a close-up, I have ringed a small part of the sponge colony which is raised above the rest. In this bit you can see the sponge structure fairly clearly. Have a look at the sponges on the Fact Sheet for comparision.

Best wishes,
Bill Rudman

Rudman, W.B., 2010 (Mar 30). Comment on Pectenodoris trilineata from Lembeh by Franco De Lorenzi. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

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