Elysia trisinuata
Baba, 1949

Order: SACOGLOSSA
Superfamily: ELYSIOIDEA
Family: Elysiidae

DISTRIBUTION

Japan, Hong Kong, Hainan Is.

PHOTO

On intertidal encrusting green alga Codium arabicum, Miura Peninsula, Japan. Photo: Yoshi Hirano.

First described by Baba (1949) from Sagami Bay, it has since been reported by Jensen (1998) from southern China. It is a fairly uniform grass green with fine orange red spots scattered all over the body and outside of the parapodia. It also has scattered white conical, unbranched papillae. The rhinophores are tipped with black or grey. The uniform green colour of the body and parapodia results from a fine network of ducts, packed with chloroplasts, scattered throughout the body wall (see lower photo). This species usually has three raised folds along the parapodial edge which is the reason for the name trisinuata. The specimen photographed has only two folds, perhaps because of damage to the posterior part of the parapodia.

See Cynthia Trowbridge's message below.

References:
• Baba, K. (1949) Opisthobranchia of Sagami Bay collected by His Majesty, the Emperor of Japan. Iwanami Shoten, 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.
• Jensen, K.R. (1992). Anatomy of some Indo-Pacific Elysiidae (Opisthobranchia: Sacoglossa [=Ascoglossa]), with a discussion of the generic division and phylogeny. Mal. Soc. London, 58: 257-96.
• Jensen, K.R. (1998) Zoogeographic affinities of Hong Kong Opisthobranchia (Mollusca, Gastropoda). In: Morton B (ed.) The Marine Biology of the South China Sea. Hong Kong University Press, Hong Kong, p 43-55.

Authorship details
Rudman, W.B., 2000 (September 24) Elysia trisinuata Baba, 1949 . [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/elystris

Related messages


Elysia trisinuata with eggs

September 5, 2002
From: Nishina Masayoshi

Dear Bill,
Here is a photo of E. trisinuata and its egg mass, on Codium to accompany my other message.

Date: 16 Aug 2002
Loc: Echizen coast, Fukui prif. Japan
Lengh: 10mm to 15mm
Depth: 4m
Water temp: 28C degree
Photo M. Nishina

Best Regards,
Nishina Masayoshi

nishina@wips.co.jp

Masayoshi, N., 2002 (Sep 5) Elysia trisinuata with eggs. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/7855

Thanks Nishina,
Bill Rudman

Elysia trisinuata - variation

September 5, 2002
From: Nishina Masayoshi

Dear Bill,
You mentioned the characteristic 3 folds on the parapodia which cannot be easily seen in the photos of Elysia trisinuata that I posted in an earlier message.

I have been wondering the same thing, And I had a chance to take a several photos of
several individuals. It seems E. trisinuata look different when they are shortened and extended. The 3 folds, can only be seen at certain angles. I also noticed that they have many fine vermilion specks scattered on the surface of the body. These are clearly visible in upper right photo. I have sent a photo showing E. trisinuata and its egg mass in a separate message.

Date: 16 Aug 2002
Loc: Echizen coast, Fukui prif. Japan
Lengh: 10mm to 15mm
Depth: 4m
Water temp: 28C degree
Photo M. Nishina

Best Regards,
Nishina Masayoshi

nishina@wips.co.jp

Masayoshi, N., 2002 (Sep 5) Elysia trisinuata - variation. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/7857

Thanks Nishina,
I have included a closeup here to show the reddish vermilion spots you mentioned. It reminds me quite a lot of Elysia maoria, but that species doesn't have the distinctive 3 folds.
Best wishes,
Bill Rudman

Rudman, W.B., 2002 (Sep 5). Comment on Elysia trisinuata - variation by Nishina Masayoshi. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/7857

RE: Elysia? from Hachijo Is, Japan

May 24, 2002
From: Nishina Masayoshi

Dear Bill,
Thanks for your comments on my message. The algae is Codium [Identified by local divers as Codium intricatum Okamura]. I personally identified the slugs as Elysia trisinuata. That tiny one (lower) is juvenile of E. trisinuata, I think.
Best Regards,
Nishina Masayoshi

nishina@wips.co.jp

Masayoshi, N., 2002 (May 24) RE: Elysia? from Hachijo Is, Japan. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/6804

Dear Nishina,
If the algae it is on is a species of Codium it is definitely unlikely to be Elysiella pusilla. Although I can't see the characteristic 3 folds on the parapodia, I am happy to identify it as E. trisinuata.
Best wishes
Bill Rudman

Elysia? from Hachijo Is, Japan

April 12, 2002
From: Nishina Masayoshi


Dear Dr.Rudman,

I don't see this animal very often.

Data:
Date: 30 Sep, 2000
Place: Sokodo Hachijo Island, Japan
Depth: 6m
Size: 10mm (lower) & 25mm (upper)
Best Regards,
Nishina Masayoshi

nishina@hpe15.wips.co.jp

Nishina, M., 2002 (Apr 12) Elysia? from Hachijo Is, Japan. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/4977

Dear Nishina,
Perhaps this is Elysiella pusilla? Was it found on the calcareous green alga Halimeda?
Best wishes,
Bill Rudman.

Rudman, W.B., 2002 (Apr 12). Comment on Elysia? from Hachijo Is, Japan by Nishina Masayoshi. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/4977

Elysia trisinuata from Sagami Bay

September 25, 2000
From: Cynthia Trowbridge


Dear Bill,
Here is another of the sacoglossans that Yoshi Hirano kindly photographed for me in Sagami Bay, during this past May. It is Elysia trisinuata Baba, 1949 (Hiramiru-midorigai)

In May 2000, we found 30 specimens on the intertidal encrusting green alga Codium arabicum on Miura Peninsula, Japan. This species is distinguished by its "thread-thin white papillae" (Jensen 1985). All our specimens were large (up to 800 mg wet weight).
Distribution: Japan, Hong Kong, Hainan (Jensen 1998).

References:
• Baba, K. (1949) Opisthobranchia of Sagami Bay collected by His Majesty, the Emperor of Japan. Iwanami Shoten, 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.
• Jensen, K.R. (1998) Zoogeographic affinities of Hong Kong Opisthobranchia
(Mollusca, Gastropoda). In: Morton B (ed.) The Marine Biology of the South
China Sea. Hong Kong University Press, Hong Kong, p 43-55.

Best wishes,
Cynthia

trowbric@ucs.orst.edu

Trowbridge, C.D., 2000 (Sep 25) Elysia trisinuata from Sagami Bay. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/3070

Thanks Cynthia,
Bill Rudman.