Elysia in Echizen cost

May 23, 2002
From: Nishina Masayoshi

Dear Bill,
We photographed many Elysia in Echizen coast in last summer(11,12 Aug 2001) and I have divided them into following groups from external features.

• P1. Translucent colourless body with white and yellow glandular? patches. Posterior foot and rhinophores are blue-black-tipped (sometimes speckled with white). [Attached images: P11,P12].
• P3. Similar to P1 but some green pigment present.
• P4. Similar to P1 but most of body with green pigment. White papillae on parapodia. [Attached images: P41, P43]
• P5. Similar to P1 but body dark green. White papillae on parapodia. [Attached images: P51,P52]

They have similarities to Elysia japonica, Elysia amakusana, Elysia abei and even Elysia cf. furvacauda. They were photographed almost on the same day and the same place on the Echizen coast. They were all approximately 10mm long.

I have no idea how to tell these animals apart. Although the body color is different, external features are all similar to each other. I feel that the white papillae on the parapodia and the white specks sometimes on the rhinophores can not be special external features for separating these animals. But I cannot say anything about their anatomy.

Best Regards,
Nishina Masayoshi

nishina@wips.co.jp

Masayoshi, N., 2002 (May 23) Elysia in Echizen cost. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/6704

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

Rudman, W.B., 2002 (May 23). Comment on Elysia in Echizen cost by Nishina Masayoshi. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/6704

Factsheet

Elysia cf. japonica

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