Dear Chay Hoon,

We have this on the Forum as Elysia cf. japonica but if you look at the discussions under that species and Elysia abei there is still no clear agreement on whether they are all colour forms of one species or not. Certainly the blue on the rhinophores and the distinct yellow spots are characteristic of Elysia cf. japonica, but we are not sure if it is the same as Elysia japonica or E. abei, or both.

Best wishes,
Bill Rudman

Thanks Nishina,
Bill Rudman

Dear Nishina
Sorry it has taken me a while to post this message. I have no problem in considering all these animals to be colour forms of one species. The differences in the amount of green pigment being almost certainly related to the amount of algal pigment in their branching digestive gland ducts. I am sure that this is the animal the Kathe Jensen considers is Elysia japonica.

The animal I have on the Forum as Elysia abei could well be an even darker colour form of your Elysia. Whether I have correctly identified it as E. abei is a separate problem for us to solve. Similarly, I don't know if the animal on the Forum as Elysia amakusana is correctly identified. From the photos on the Forum it seems that it could be different. There seems to be quite a dense cover of pigmentation on the skin, and the papillae are much more extensive than the arrangement on the animal in your message.

The problem then is, what is the best name for this species, and if we can correctly identify E. amakusana and E. abei, are they the same or different?
Best wishes,
Bill Rudman

Thanks Kathe,
Your mention of the constriction in the pericardial hump etc to add some weight to your suggestion that this animal could be Elysia japonica. I guess we have to see if anyone can find a specimen of it in Japan, and find out whether either of the other potential candididates for the name, E. amakusana and E. abei, have a constriction on the pericardial hump and similar dorsal vessels.
Inadequate descriptions are a pain,
Bill Rudman

Dear Nishina,
Eliot (1913) published a paper based on preserved specimens in the collections of the Imperial University, Tokyo. Some species seem to have been accompanied by colour sketches, but for many of the specimens there seems to have been no accompanying information on the living animal. The specimens of Elysia japonica fall into that category. As I said earlier there seems to be no way we can easily identify Eliot's species.

Eliot's description is relatively short so I have copied it below:
======================
Elysia japonica sp. nov.
18 specimens. Locality? (No label found). The largest is about 20mm long and the wings are moderately ample. In two specimens which were dissected, the radula was found to contain six teeth in the ascending row, 15 in the descending and about 20 more of various sizes lying in a heap. The structure of the radula and the shape of the teeth is as usual in the genus. No denticles are to be seen. I think that this form is probably a new species distinguished by the following characters:
(1) Colour: In all the specimens the rhinophores and the tip of the tail are conspicuously black or very dark brown. Otherwise the colour is uniform and in the best preserved specimen is yellowish brown. The wings have no coloured borders and the head and pericardium are of the same colour as the dorsal surface.
(2) The arrangement of the dorsal surface. This is similar in all the specimens and I have not seen it in any other species. The pericardium is not ovate but is constricted in the middle. Its length is greater than its breadth but it is short in comparison with the length of the whole animal. The dorsal ridges which run into it are very distinct and the two hindmost, which run backwards towards the tail, are parallel to one another and enclose an area which is differentiated from the back and forms a smooth trench.
• Eliot, C.N.E. (1913) Japanese Nudibranchs. Journal of the College of Science, Tokyo Imperial University, 35: 1-47. [pp46-7]
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There are no illustrations. Basically we do not know what the animal looks like alive, where in Japan it was collected, or anything meaningful about its anatomy. My feeling is that this name is unidentifiable and should be ignored. It is possible that some of the original specimens still exist. If so I guess it might be possible to dissect them and see if there are any recognisable anatomical characters which could be used to identify the species. If the original type material is shown to be lost then it is possible under the International Rules for a research worker to choose another specimen and designate it to be the neotype of the species. However since neither we, nor Eliot, had any idea of the animal's colour or where it came from in Japan, it seems better to just ignore his name.
Best wishes,
Bill Rudman

Dear Leslie,
I asked Kathe Jensen for advice on this one. She thinks it is possibly Elysia japonica. Have a look at her separate message.
Best wishes,
Bill Rudman

Thanks Kathe,
One value of the Forum is that by building up a collection of colour photos of these species it must surely help to sort out some of the names of the similarly coloured species. I note in your 1985 Hong Kong paper that you suggest that both E. amakusana and E. abei are both probably synonyms of E. japonica. If the identifications on the Forum, based on Japanese usage, are correct then it seems that they are probably distinct species.

I am a little bit concerned with your suggestion that it is possible to identify Eliot's Elysia japonica. The colour description was made from apparently preserved animals
"In all the specimens the rhinophores and tip of tail are conspicuously black or very dark brown. Otherwise the colour is uniform and the best preserved specimen is yellowish brown ....".
If as you say, the radular description is not likely to be accurate, then we have no information in Eliot's description on which to base an identification other than that it was from Japan. I feel it would be better to discard Eliot's name as unidentifiable and use a later name if there is one.

Concerning the species Brian Brandley worked with. There is no problem with identifying it. the problem is whether it has a name. While he was working on this species, he asked me for help in identifying it. It had previously been tentatively identified as E. furvacauda in New South Wales, but I felt it had significant differences to the original description by Burn. Unfortunately no material was available of 'typical' E. furvacauda for comparison. For this reason I suggested Brian identify his animal as Elysia cf. furvacauda and deposit voucher specimens in the Australian Museum collections. I photographed these specimens alive - see top of Elysia cf. furvacauda page - so that they would be identifiable to later workers. Throughout the paper they are referred to as Elysia cf. furvacauda and the identification problem discussed.
Best wishes,
Bill Rudman