Re: Roboastra gracilis eating Nembrotha kubaryana

February 14, 2006
From: Rie Nakano


Concerning message #15816:

Dear Dr.Rudman and Mr.Ross Gudgeon,
I think this little predator is Roboastra luteolineata, not R. gracilis.

Here are two photos for comparison which were taken at the same place, at the same time.

Upper: Roboastra luteolineata is 40mm.
Lower: R.gracilis is 30mm.
Locality: Zamami Is., 7 metres, Okinawa, Japan, Pacific Ocean, Summer, 2004, Rocky shore. Photographer: Rie Nakano

Juvenile R. luteolineata is just like R. gracilis, but the color of the gills is obviously different.

Sincerely,
Rie Nakano

.

rie@divers.ne.jp

Rie Nakano, 2006 (Feb 14) Re: Roboastra gracilis eating Nembrotha kubaryana. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/15851

Dear Rie,
Thanks for your comments. I had my doubts about the identity of this little Roboastra but decided on R. gracilis for a number of reasons.

I wondered about the gills, but not so much with the colour, which seems ok, but with the number of gills. I usually expect there to be three but Pola, Cervera & Gosliner (2005) say there can be up to six. The feature that made me decide it was R. gracilis was the way the yellow lines joined in the midline behind the gills, as you can see in your photo of R. gracilis. In R. luteolineata the lines seem to run parallel on either side of the midline.

I may be quite wrong. Perhaps Marta, Lucas or Terry can give us their opinion.

  • Pola, M.., Cervera, J.L. & Gosliner, T.M. (2005) Review of the systematics of the genus Roboastra Bergh, 1877 (Nudibranchia, Polyceridae, Nembrothinae) with the description of a new species from the Galápagos Islands. Zoological Journal of the Linnean Society,144, 167–189. With 12 figures

Best wishes,
Bill Rudman

Rudman, W.B., 2006 (Feb 14). Comment on Re: Roboastra gracilis eating Nembrotha kubaryana by Rie Nakano. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/15851

Factsheet

Roboastra gracilis

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