Goniobranchus setoensis (Baba, 1938) [Glossodoris]

Click the thumbnail photos to enhance!

Goniobranchus setoensis is characterized by a translucent greyish body with an orange-brown mantle margin. There is a thin opaque white line encircling the mid-dorsal region, running from the rhinophores parallel to the mantle margin, behind the gills to the other rhinophore. A medial thin opaque white line forms a "Y" just in front of the translucent gills. Submarginal are large purple and minute opaque whit spots. There are no purple spots in the greyish mid-dorsal region, which is encircled by a opaque white line.
This picture shows a 3 mm juvenile specimen.
Very similar is Goniobranchus decorus (Pease, 1860) which differs by having purple spots also in the greyish mid-dorsal region, and by having purple spots in the white 'Y".
The Sea-Slug Forum lists both species as Chromodoris decora and dicusses the colour variations at Identity of Chromodoris decora , let me quote:"..all these forms seem to represent variations of one species." and "Baba himself (1953) suggested it should be considered a synonym of C. decora."
IPN lists them seperate with the comment: "Additional work is necessary to determine whether these are color variants or distinct species."
Scott and Jeanette Johnson discuss it at Underwater Kwajalein with many pictures, they think these species to be distinct.
I followed IPN and posted it as Goniobranchus setoensis (Baba, 1938) [Glossodoris].
This species was posted on 17 July 2011 at these websites as Chromodoris setoensis (Baba, 1938) [Glossodoris],
R.F. Johnson & Gosliner (2012) moved it to the reerected ("rescued from synonymy") genus Goniobranchus  Pease, 1866.
Gosliner, Terrence M., David W. Behrens & Ángel Valdés. 2008. Indo-Pacific Nudibranchs and Sea Slugs.
Sea Challengers Natural History Books. Gig Harbor, Washington. 426pp.
Rebecca Fay Johnson & Terrence M. Gosliner. 2012.
Traditional Taxonomic Groupings Mask Evolutionary History:
A Molecular Phylogeny and New Classification of the Chromodorid Nudibranchs. online at
and move Chromodoris setoensis to the reerected ("rescued from synonymy") genus Goniobranchus  Pease, 1866.
More information on Goniobranchus decorus as Chromodoris decora are on Bill Rudman's Sea-Slug Forum!
How to cite:
Köhler, E. (2019), published 16 January 2019, Goniobranchus setoensis (Baba, 1938)
available from https://www.Philippine-Sea-Slugs.com/Nudibranchia/Doridina/Goniobranchus_setoensis.htm


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