Is this Cyerce nigricans?

April 25, 2001
From: Nishina Masayoshi

Hello Dr.Rudman,
Is this Cyerce nigricans? What I have noticed is that the cerata are not flat, rather say looks like a balloon. The rhinophore color is brighter than the colour of the body. Size is about 1cm, so it is also considered some juvenile.

I believe that Cyerce nigricans has much colour variation, but I have never seen this color pattern and figure of the cerata. I'm sorry for the photograph which is not in focus.

The animal was found by Nishina Chikako, 15 April 2001, at Sokodo, Hachijo Island, Japan. It was at about 6M depth where it was moving on sand surrounded by the rocky reef.
Water Temp: 18-20C degree.

Sincerely yours
Nishina Masayoshi

Masayoshi, N., 2001 (Apr 25) Is this Cyerce nigricans?. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Nishina,
Your animal has colour similarities to C. nigricans but as you say, the differences are quite considerable. I also agree that the inflated cerata are unlike those of C. nigricans. It would be interesting to know more about the juvenile colour variation in Cyerce nigricans and Cyerce nigra.

I suspect your animal may be a colour variation of C. kikutarobabai Hamatani 1976 which I have just added to the Forum because of your message. You will see from the photos on the C. kikutarobabai Page that there are some important similarities. In both your animal and C. kikutarobabai the head, rhinophores and oral tentacles are purple and spotted with white. In both species, the cerata are inflated, have yellow spots on both sides, and have an orange or orange-yellow edge to the cerata. Your animal differs, however, in having a black, rather than purple, background colour on the cerata.

There are too few records of C. kikutarobabai for us to know how variable in colour it is, and whether your animal represents another new species or just a colour variant of C. kikutarobabai or even C. nigricans. Perhaps someone can give us some more information
Best wishes,
Bill Rudman

Rudman, W.B., 2001 (Apr 25). Comment on Is this Cyerce nigricans? by Nishina Masayoshi. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

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