Siphopteron pohnpei from Japan.

January 20, 2004
From: Jun Imamoto

Dear Bill,
Here is a report of the distribution of a Siphopteron from Japan. It was discovered under a stone in shallow water in a sheltered bay. 2 individuals were found quite close to each other. The seaweed Ulva is very abundant in this place at this time of the year.
I think that this sea slug is Siphopteron pohnpei. A gill can be confirmed in the lower left photo.

Amami-Ooshima Islands, Kagoshima, Japan.
Size: approx 4mm, Depth: 1 m. Temperature: 21 C. 15 Jan 2004

Best Regards,
Jun Imamoto

Imamoto, J., 2004 (Jan 20) Siphopteron pohnpei from Japan.. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Thanks Jun,
Yes this does seem to be S. pohnpei. As you will be aware I am very interested in finding out just what gastropterids feed on. As we don't seem to have found any identifiable stomach contents in preserved animals I have wondered whether they feed on small flatworms. I am not sure whether it is significant or not, but in your photo alongside, the animal seems to be interested in the polychaete tube worm just in front of it [see close-up inset]. I guess its possible that gastropterids eat small polychaete worms. It's certainly a possibility worth looking out for.
Best wishes
Bill Rudman

Rudman, W.B., 2004 (Jan 20). Comment on Siphopteron pohnpei from Japan. by Jun Imamoto. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

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