Bornella japonica? from Japan

September 12, 2001
From: Nishina Masayoshi

Dear Dr.Rudman,
Here are some photos of the Bornella that I have seen in Japan.

UPPER RIGHT: Echizen coast, 12 Aug 2001. Length is 50mm and it's common in Echizen. Photo: Nishina Masayoshi

LOWER LEFT: Hachijo Island on 18 Dec 2000. Length is 30mm and it's common in Hachijo. Photo: Nishina Masayoshi

LOWER RIGHT: Echizen coast on 12 Aug 2001.
Length is 40mm. Photo: Nishina Chikako

Best Regards,
Nishina Masayoshi

Nishina, M., 2001 (Sep 12) Bornella japonica? from Japan. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Nishina,
I think this is probably Bornella japonica. I beginning to think that the best distinguishing feature is not three pairs of dorsolateral processes ('cerata'), but their colour. In all the photos I have seen which seem to fit B. japonica, the dorsolateral processes are white and don't have the distinctive subapical orange band found in Bornella stellifer. The rhinophore stalks are also white.

Baba also described secondary papillae on the most posterior papilla on the rhinophore stalk. In your upper right photo [see inset] and lower right, secondary papillae are clearly present. Baba (1949) and Atsushi Ono (1999) both publish pictures of animals that are clearly Bornella stellifer, so it seems there are two very similarly coloured species of Bornella to be found commonly in Japan.
Best wishes,
Bill Rudman

Rudman, W.B., 2001 (Sep 12). Comment on Bornella japonica? from Japan by Nishina Masayoshi. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from


Bornella japonica

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