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There was no size recorded for this specimen, but it is obviously small, most probably a juvenile.
This species is Gymnodoris sp. 12 in IPN at page 152, it is known from the Red Sea and from the Marshall Islands.
Gosliner, Terrence M., David W. Behrens & Ángel Valdés. 2008. Indo-Pacific Nudibranchs and Sea Slugs. Sea Challengers Natural History Books.
Gig Harbor, Washington. 426pp.
More informations on Gymnodoris sp. 09 as Gymnodoris sp. 2 are at Bill Rudman's Sea-Slug Forum!