Elysia chilkensis
Eliot, 1916
Order: SACOGLOSSA
Superfamily: ELYSIOIDEA
Family: Elysiidae
Jensen (1985), reported this species from Hong Kong. However, Eliot's description, based on a single animal, lacks all the information required for a reliable identification. Until the elysiid fauna of the type locality - Chilka Lake, north-eastern India, is examined, I suspect Eliot's Elysia chilkensis is unidentifiable.
Here are the main points of the original description, which was based on a single specimen, and there were no accompanying images:
"A single specimen taken among weeds in a few inches of water close to the shore .... Chilka Lake, 20 March 1914.
Form of body elongate and narrow, pointed behind but not produced. Tentacles very slender, tapering, pointed.
Colouration:- Dorsal surface dull moss-green marbled with a darker shade and dotted with white. Front of head between tentacles brownish, the brownish shade gradually disappearing behind head on sides of body. A colourless streak along the mid-dorsal line behind the head; a broad dark brown bar along each side of the head interrupted by a whitish streak containing the orifice of the tentacle. Ventral surface greenish.
The preserved specimen is 17mm long ... The animal is in most respects a typical Elysia but it has long, tapering tentacles which appear to be only slightly grooved, whereas in most species the tentacles are rather short and distinctly folded or auriculate." Eliot, 1916.
Reference:
• Eliot, C.N.E. (1916). Mollusca Nudibranchiata, Fauna of the Chilka Lake. Memoirs of the Indian Museum, 5: 375-380
• 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.
Rudman, W.B., 2003 (June 10) Elysia chilkensis Eliot, 1916. [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/elyschil
Related messages
Re: Elysia hirasei vs Elysia chilkensis
May 18, 2006
From: Kathe R. Jensen
Concerning message #16607:
Dear Cynthia and Bill,
I do have a picture of Elysia chilkensis. Unfortunately I didn't take the original, Sherman Bleakney from Acadia University, Nova Scotia, Canada did. He has been retired for several years and I don't know his current address. However, I cannot imagine that he would object as long as he is acknowledged for the picture - especially since he also gave me all of his field notes and specimens from his trip to Hong Kong. The picture was taken on 2 January 1981. The specimen had been collected in tide pools at Tsim Bei Tsui, Deep Bay, Hong Kong. I looked very carefully for it when I first visited Hong Kong in 1983, but didn't find any (instead I got Gascoignella aprica from that locality).
Locality: Tsim Bei Tsui, Deep Bay, intertidal, Hong Kong, South China Sea, 2 January 1981. Length: 7 mm. Photographer: J. Sherman Bleakney.
As you can see it differs in a number of ways from E. hirasei: the anterior margin of the head is deeply cleft between the rhinophores, the rhinophores are very long and thin, the anterior foot corners are pointed. If I remember right, it didn't have any papillae on the parapodia, but I may be wrong about that. Thus I doubt that E. chilkensis and E. hirasei are the same species - but I won't completely rule it out.
Best wishes,
Kathe
krjensen@snm.ku.dk
Dear Kathe,
Thanks for the photo. All we need to do now is go to Chilka Lake and find an animal which fits Eliot's rather poor description of E. chilkensis.
Best wishes,
Bill Rudman
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?
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Eliot, C.N.E. (1916). Mollusca Nudibranchiata, Fauna of the Chilka Lake. Memoirs of the Indian Museum, 5: 375-380
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Hirasé, S. 1927. Figuraro de Japanaj Bestoj, Moluskoj.
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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
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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!
Cordially,
Cynthia
trowbric@yahoo.com
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/16607Dear 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
