Information on Pseudobornella orientalis

May 14, 2002
From: Nishina Masayoshi

Dear Bill,
I've the opportunity to discuss with Pamun, Yamada, Kinoshita, Kurihara, etc... their observations on Pseudobornella orientalis.

P.orientalis is often found on sandy bottoms in Spring. It is not a rare species in this period at Osezaki beach, Izu. Most times they were found on sands. It is easier to find it at night time than during the day so ir may be a nocturnal animal.

The average length of an adult is between 20mm to 30mm. When P. orientalis is fully grown, their mantle becomes like a film like an octopus has. P. orientalis can use it for floating. Kurihara has a good photo. It shows the film-like mantle. P. orientalis seems to live on or in the sand, and it may swim or float underwater occasionally with the film-like mantle. Some animals dislikes the light of a
flashlight and bury in the sand but some of them don't seem to notice.

P. orientalis is rarely found on the hydroid Tubularia mesembryanthemum but it does not seem to eat it. From Kurihara's observation, the thread on the rhinophores retracts and shrinks when something (like a floating minute animal) touches it but then it immediately extends out as it was.

Best Regards,
Nishina Masayoshi

Masayoshi, N., 2002 (May 14) Information on Pseudobornella orientalis. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Thanks Nishina,
It is indeed a fascinating animal. As I said to Tomohiko Kurihara I am pretty sure the film-like flaps, which as you say do remind us of an octopus, are the edge of the foot rather than the mantle. In these animals the 'edge' of the mantle is represented by the row of 'cerata/gills'.
Best wishes,
Bill Rudman

Rudman, W.B., 2002 (May 14). Comment on Information on Pseudobornella orientalis by Nishina Masayoshi. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

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