Elysia hirasei vs Elysia chilkensis

May 15, 2006
From: Cynthia Trowbridge

Dear Bill,

I was so excited when I discovered the page for Elysia hirasei. Of the 3 species initially identified as Elysia viridis in Japan, this species has been a mystery to me as I have never seen it.

After a bit of literature work, I have learned that Shintaro Hirasé reported a 15 mm Elysia viridis from Kanagawa-ken (Japan). This species was illustrated in the 1951 book (revised by Taki) and probably in the 1927 publication as well (I have not seen this yet). Due to the small size of the figure, it is hard to tell if it is Elysia hirasei or not. But I assume that it is the same given that Baba named the species after Hirasé.

After seeing the photograph of Elysia hirasei on the Forum, I was struck by its similarity to what Kathe was calling Elysia chilkensis Eliot, 1916 (Jensen 1985, PP. 81-82 and Fig. 3). I understand your concern, Bill, [expressed in E. chilkensis Fact Sheet] with Eliot's original descriptions.  However, have you noticed the similarities between Kathe's species and E. hirasei?

  • Eliot, C.N.E. (1916). Mollusca Nudibranchiata, Fauna of the Chilka Lake. Memoirs of the Indian Museum, 5: 375-380
  • Hirasé, S. 1927. Figuraro de Japanaj Bestoj, Moluskoj.
  • Hirasé, S. 1951. An illustrated handbook of shells in natural colors from the Japanese Islands and adjacent territory, revised and enlarged by I Taki. Bunkyokaku, Tokyo
  • Jensen, K.R. (1985) Annotated checklist of Hong Kong Ascoglossa (Mollusca: Opisthobranchia), with descriptions of four new species. [In:] Proceedings of the 2nd International Workshop on the Malacofauna of Hong Kong and Southern China, Hong Kong, 1983. (Eds: Morton, B.; Dudgeon, D.) Hong Kong University Press, Hong Kong, 77-107.

Any thoughts?
All the best and thanks!


Trowbridge, C.D., 2006 (May 15) Elysia hirasei vs Elysia chilkensis. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/16607

Dear Cynthia,
Perhaps if we are lucky, Kathe will have some slides of the Hong Kong animals she can share with us. Although it might be possible to suggest a similarity between her animals and E. hirasei, I don't think we are going to have much luck linking any species with Eliot's E. chilkensis, considering how little information was contained in the original description.
Best wishes,
Bill Rudman

Rudman, W.B., 2006 (May 15). Comment on Elysia hirasei vs Elysia chilkensis by Cynthia Trowbridge. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/16607


Elysia chilkensis

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  1. Re: Elysia hirasei vs Elysia chilkensis
    From: Kathe R. Jensen, May 18, 2006

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