Ercolania subviridis ? from Okinawa

March 22, 2005
From: Cynthia Trowbridge

Dear Bill and Kathe,

I am writing about another of the Ercolania a species that the Hiranos, their students, and I found in Okinawa in the last week or so. We think this species most closely fits the description of Ercolania subviridis (Baba 1959) for the following reasons:

  • Body yellowish white
  • Deep/dark green diverticula
  • Cerata have dark green veins internally
  • Deep green longitudinal lines on outer surface of cerata (see close-up)
  • Rhinophores long, slender, and simple
  • Foot-corners rounded

The longitudinal diverticula are the key identifying feature, even in Baba's black and white drawing. I removed one ceras and did a "squash" slide mount (both lit from above and below) to illustrate the diverticula.

Baba also described a red marking at the anterior end of pericardial prominence. We saw one at the posterior end (very faint) but do not recall about an anterior marking. I will mention a similar red patch (or patches) in another co-existing Ercolania species (see separate message).

Locality: west coast of Okinawajima, Okinawa, Japan, East China Sea. Depth: 1 m. Length: several mm (data in Japan). 10-15 March 2005. low intertidal to shallow subtidal rocky shores. Photographer: Tomohiro Watanabe

I am presenting this species with a cordial request for informal identification. My primary objective is to illustrate to colleagues what Ercolania subviridis may be (hopefully). Various web sites and books illustrate a wide range of species under this name (sort of like the "Placida dendritica " issue). It would be great if we could standardize what is recognized by this name.

Baba mentioned Ercolania subviridis on a "green alga"... our specimens were from Boodlea sp. in Okinawa. In many areas of Japan, Boodlea occurs in high-shore pools. However, in Okinawa, the alga is low on the shore or in the shallow subtidal. We have confirmed our species feeds on this alga.

If colleagues from Japan have verified or unverified records of this species, I would grateful for details. Thanks!

  • Baba, K. (1959) The family Stiligeridae from Japan (Opisthobranchia - Sacoglossa). Publications of the Seto Marine Biological Laboratory, 7: 327-334

All the best,
Cynthia

trowbric@onid.orst.edu

Trowbridge, C.D., 2005 (Mar 22) Ercolania subviridis ? from Okinawa. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/13387

Dear Cynthia,
Thanks for another interesting species. It certainly seems to fit Baba's description. The reddish mark you mention can be see in Tomohiro Watanabe's excellent photo of the whole animal, ain the midline about halfway down the body. I've also included a close-up of the anterior cerata. As well as showing the green 'lines' they also show a central core which I think in part is a branch of the albumen gland. The sabot-shaped radula teeth in Baba's description woudl suggest Ercolania is the correct genus for this species. - but we should wait for Kathe's comments.

I can only agree with your excellent aim to make it easier to identify these fascinating animals.
Best wishes,
Bill Rudman

Rudman, W.B., 2005 (Mar 22). Comment on Ercolania subviridis ? from Okinawa by Cynthia Trowbridge. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/13387

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Ercolania subviridis

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