Selection: Okenia japonica  
Okenia japonica  Baba, 1949

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Okenia japonica is characterized by a translucent whitish/gray body and white rounded papillae along the edge of the mantle, and by a single medial papilla in front of the gills. There is a white band along the edge of each gill. This is a small species, IPN writes length 15 mm, the Forum: up to 8 mm long.
There are many pictures of this species from Japan online at
Gosliner, Terrence M., David W. Behrens & Ángel Valdés. 2008. Indo-Pacific Nudibranchs and Sea Slugs. Sea Challengers Natural History Books.
Gig Harbor, Washington. 426pp.
Rudman, W.B., 2004 (December 21) Okenia japonica Baba, 1949. [In] Sea Slug Forum. Australian Museum, Sydney.
Available from
More information on Okenia japonica are on Bill Rudman's Sea-Slug Forum!
How to cite:
Köhler, E. (2017), published 10 November 2017, Okenia japonica  Baba, 1949
available from