Cratena affinis? from Japan

November 26, 2002
From: Jun Imamoto

Dear Bill,
I found this sea slug which looks like the original description of Cratena affinis. It seems to differ only in the colour at the base of the cerata. I would be very happy to hear your comments.

Osezaki, Suruga Bay, Japan, 9 Nov. 2002. Size approx: 7mm., Depth: 9m (Night Scuba Diving). Temperature: 17 C

Best Regards,
Jun Imamoto

Imamoto, J., 2002 (Nov 26) Cratena affinis? from Japan. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Jun,
Thanks very much for these photos. I agree that this fits Baba's description very well. It differs, as you say in the internal colour of the cerata. Baba describes the digestive gland colour as 'dark', and they are blackish-brown in the illustration. I am sure the difference in your animal is because it has not fed recently and its digestive gland ducts have no food in them. I suspect the other photos on this page, which I have previously identified as C. affinis, are variants in which the white lines on the cerata are absent or replaced by white spots.
Best wishes,
Bill Rudman

Rudman, W.B., 2002 (Nov 26). Comment on Cratena affinis? from Japan by Jun Imamoto. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from


Cratena affinis

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