Goniobranchus setoensis (Baba, 1938)
25mm

Goniobranchus setoensis is similar to G. decorus and many nudibranch workers think they both are variations of the same species. Why I disagree with this is discussed under G. decorus, and numerous photos are supplied below to illustrate the diversity within the species. Of 29 specimens measured (just some of the many observed), the largest was 25mm. However, it does get a bit larger. The two below are feeding on a yellow sponge.

The specimen immediately below came from a Kwajalein Atoll lagoon reef under a rock in about 5m of water on 23 February 2009.

Rarely this species has an overall yellow tinge.

Mating pair.

The next photo shows a pair of specimens from Majuro observed by Ken Cone and Beth Van Zummeren.

This one appears to be feeding on the purple sponge Chelonaplysilla violacea.

This one was not eating that red sponge, but instead just starting to crawl over it.

The young specimen below was photographed on 2 March 2009 feeding on yellow sponge on a Kwajalein Atoll lagoon reef at a depth of about 4m.

The specimen below was observed eating a gray sponge on a Kwajalein western lagoon reef on 29 August 2009. The hole in the lower center of the sponge is where the nudibranch was grazing before it was disturbed by the photographer. Note that the structure of the gray sponge is very similar to the yellow sponge the animal above is eating. They may be color forms of the same species.

One eating a similar gray sponge.

Created 19 December 2005
Updated 30 October 2021

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