New? Costasiella from Kerama Island

September 12, 2005
From: Atsushi Ono

Dear Bill,
I found an interesting Sacoglossan species the other day. At first, I was
convinced that this was Stiliger ornatus. However, I was surprised to see a detailed image of the head after the film was developed. This is a species of Costasiella. It was definitely on Avrainvillea erecta.. Two individuals were observed, and one was photographed

Data: Kerama Is. Japan. Depth 25 m 7 July 2005. Photo: Atsushi Ono

And though it is a personal opinion... Costasiella pallida Jensen, 1985
is very similar to C. formicarius (Baba, 1959). [Please refer to
Baba,1959 The family Stiligeridae from Japan Pablication of the Seto
Marine Biological Laboratory,

Atsushi Ono

Ono, A., 2005 (Sep 12) New? Costasiella from Kerama Island. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Atsushi,
This is indeed an interesting discovery. It is possibly Costasiella mandorahae Jensen, 1997, but I would like to see Kathe Jensen's colour slides before commenting further. In her description she says the " body is very lightly coloured ... on the anterior surface of the head is a median orange stripe ... in some specimens there also thin orange stripes along the antero-lateral ridges of the head ... cerata have white tips and a subterminal orange band.. a few iridescent blue dots found on cerata. "

In her drawing there is a broad dark stippled band on the cerata. I don't know what that represents. It is possible your animals are a more densely pigmented form of the same species. Other than that I can find no other species approaching your animal. Until I hear from Kathe I will leave this is the unidentified group.

  • Jensen, K. R. (1997)  Sacoglossa (Mollusca, Opisthobranchia) from the Darwin Harbour Area, Northern Territory, Australia. In: Proceedings of the Six International Marine Biological Workshop. The marine flora and fauna of Darwin Harbour, Northern Territory, Australia. (Eds: Hanley, J.R., Caswell, G., Megirian, D., Larson, H.K.) Museums and Art Galleries of the Northern Territory and the Australian Marine Sciences Association: Darwin, Australia, Darwin, 163-186.

Best wishes,
Bill Rudman

Rudman, W.B., 2005 (Sep 12). Comment on New? Costasiella from Kerama Island by Atsushi Ono. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from


Costasiella sp. 4

Related messages

  1. Re: New? Costasiella from Kerama Island
    From: Kathe R. Jensen, September 13, 2005

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