Protaeolidiella atra from Japan

November 4, 1999
From: Yasuhiro Shirai

Dear Bill.

Thank you for your message. I am happy to put my photos on your Forum. I will send other sea slug photos.

I saw your website about Protaeolidiella atra. I have seen P. atra two times in this year, and they did not have a white line on their back.

I have attached their photos. If you are going to use them in your Forum,I am very happy.

I took the LOWER photo at Nansei, which is on the east side of Kii Peninsula, between Kusimoto and Nagoya. It was on the hydroid, depth 13m, water temperature 18C, about 50mm length, June 1999.

I took the UPPER photo at Shijima, which is about 20km east of Nansei. This one was also on the hydroid, depth 16m, water temperature 25C, about 50mm length, Aug 1999.

Best wishes.
Yasuhiro S.

Shirai, Y., 1999 (Nov 4) Protaeolidiella atra from Japan. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Yasuhiro,
Thank you very much for sending the interesting photos of Protaeolidiella atra. When I looked at your website after your last message, I was very interested to see the photos of Protaeolidiella. When I reviewed these animals (Rudman, 1990) I considered the Japanese P. atra, without a white stripe, and the Australian P. juliae, with a white stripe to be the same species. The white-striped form is quite common throughout the indo-West Pacifc. Dr Baba (1992) still considers the Japanese animal, illustrated here, to be a distinct species. From Baba's illustrations, there do not seem to be any easily defined anatomical differences. If any one has seen both colour forms together, I would be very interested to hear of it. Dr Baba reports both striped and unstriped animals from Japan. One interesting difference is that the unstriped animals grow to over 50mm which is about twice as long as the largest striped specimen I have seen. Perhaps the striped animals are only found on Solanderia fusca.

The hydroid in Yasuhiro's photos is identified in Baba (1992) as Solanderia secunda (Inaba).

Best wishes,
Bill Rudman.

Yasuhiro's website is at It is mostly in Japanese, but there is a section with nudibranch photos at:

•Baba, K. (1992) Comment on the taxonomy of Protaeolidiella atra Baba, 1955 and an allied species from Japan. Report of the Sado marine Biological Station, Niigata University, 22: 29-35.
•Rudman, W.B. (1990.) Protaeolidiella atra Baba, 1955 and Pleurolidia juliae Burn, 1966; one species, two families (Nudibranchia). Journal of Molluscan Studies, 56(4): 505-514.

Rudman, W.B., 1999 (Nov 4). Comment on Protaeolidiella atra from Japan by Yasuhiro Shirai. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

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