Flabellina riwo  Gosliner & Willan, 1991

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Flabellina riwo is characterized by an network of opaque white lines on the translucent brownish body. The cerata are in the basal half translucent whitish-tan, medial is a translucent purple ring, followed by a diffuse bright blue band, diffusing into a yellowish-white subapical band, the apices are translucent orange-pink. It has long oral tentacles with flattened, paddle-shaped tips. There is a purple band on the pinkish oral tentacles near the head, some specimens have a second medial purple band. It has perfoliate rhinophores, which are basally translucent, the medial region is mottled brownish-tan, subapical is a pinkish band, the tips are translucent.
It is similar in shape to the smaller Flabellina bicolor, including the long oral tentacles with flattened tips. It differs by the colour pattern.
One more species with that kind of oral tentacles is Flabellina bilas.
In IPN is a picture of a specimen which lacks the left oral tentacle, and the right oral tentacle does not show the distinctive purple bands, which are also not mentioned in the text.
Gosliner, Terrence M., David W. Behrens & Ángel Valdés. 2008. Indo-Pacific Nudibranchs and Sea Slugs. Sea Challengers Natural History Books.
Gig Harbor, Washington. 426pp. at page 352
This picture shows 4 specimens ranging in size from 5 to 7 cm length.
More information on Flabellina riwo are on Bill Rudman's Sea-Slug Forum!
How to cite:
Köhler, E. (2016), published 3 November 2016, Flabellina riwo  Gosliner & Willan, 1991
available from https://www.Philippine-Sea-Slugs.com/Nudibranchia/Dexiarchia/Flabellina_riwo.htm