Pseudobornella orientalis from Japan

May 1, 2002
From: Tomohiko Kurihara

Dear Bill.
Here are photos of Pseudobornella orientalis Baba, 1932 I found at Osezaki, Izu Peninsula, Japan. It was crawling on a sandy bottom. It had a strange tentacle on each rhinophore which can stretch out and pull in when I touched it.

Another time I saw it floating in the sea. Also I think, it used the mantle-margin for floating. Mantle-margin was very wide open while floating. When it wanted to land on the bottom it closed the mantle-margin and changed shape to kind of U-shape. After it was able to land on the bottom.
The 'swimming photos' were taken at Osezaki, Suruga Bay, Izu Peninsula, Japan. Length: about 30mm. 10 April 2002

Best Regards,
Tomohiko Kurihara

Kurihara, T., 2002 (May 1) Pseudobornella orientalis from Japan. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Tomohiko,
Thanks for these interesting photos and observations. With your message and Nishina's we have learnt more about this species in a few weeks than we have in the last 60 years since it was first described. It certainly has similarities to the other opisthobranchs that live in sandy habitats. It would be wonderful to find out how it uses the long retractile tentacle on its rhinophores. Perhaps it searches out for its hydroid food. I suspect the wide flaps which you describe developing when it is swimming/floating are in fact the edge of the foot rather than the mantle for these animals don't really have a mantle edge. Again, other sand-dwelling species have very a very large foot and some of them, such as Euselenops and Kalinga ornata use the extended edges of the foot to swim/float.
Best wishes,
Bill Rudman

Rudman, W.B, 2002 (May 1). Comment on Pseudobornella orientalis from Japan by Tomohiko Kurihara. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

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