Trapania darwini
Gosliner & Fahey, 2008

Suborder: DORIDINA
Family: Goniodorididae


 Known from the Galapagos Islands, tropical eastern Pacific.


Upper: CASIZ 079163, Isla Espanola, Galapagos Islands, 7 mm. Photo: T. Gosliner. Lower: CASIZ 172859. Radular morphology. Scale =10 µm. [From Gosliner & Fahey 2008: Fig. 26C,D].

The body is translucent white with a roughly symmetrical pattern of brown elongate patches of brown which coalesce with each other. The brown patches are punctuated with elongate white spots of varying size.  The
posterior tip of the foot is yellow. The oral tentacles are brown with a white tip and the dorso-lateral processes, the rhinophores and the gills are translucent clear with yellow tips.

The living animals grow to at least 9 mm in length.

Gosliner & Fahey mention that this species closely resembles Trapania goslineri Millen and Bertsch, 2000 from the Pacific Coast of Baja California and mainland Mexico. This is a view which I strongly agree with. In external colour the difference is that the brown pigmentation in T. goslineri forms solid elongate brown spots, but the arrangement of these brown marks is almost identical to those of T. darwini. They also say that the radular morphology of T. darwini most closely resembles T. goslineri. However they consider the difference in denticulation to be significant. However the differences they mention can be found within their photos of two different parts of the radula of a specimen of T. darwini.  I would not be surprised if further collecting along the tropical eastern Pacific coast were to show these two 'species' were colour variants of one.

  • Gosliner, T.M. & Fahey, S.H. (2008)  Systematics of Trapania (Mollusca: Nudibranchia: Goniodorididae) with descriptions of 16 new species Systematics and Biodiversity, 6 (1): 53-98
Authorship details
Rudman, W.B., 2008 (March 10) Trapania darwini Gosliner & Fahey, 2008. [In] Sea Slug Forum. Australian Museum, Sydney. Available from

Related messages

Trapania darwini? from the tropical eastern Pacific

March 13, 2008
From: Alicia Hermosillo

Dear Bill,

Last year I posted a BOW (Branch of the Week ) in Mike Miller´s site. It was about these white background colored Trapania in the tropical eastern Pacific. When you find one, it looks easy to tell them apart, but when you begin comparing pictures, they are very different from each other. Anyways, I thought I had found Trapania goslineri but Dave and Terry did not agree with me ... I did some research and came up with a very confusing explanation of the known similar species. Well, then I find these guy, which does not apply to the above. Regardless, I think it is gorgeous and wanted to share it.

Locality: Islas Marietas, Puerto Vallarta, 30 feet, Jalisco-Nayarit, Mexico, tropical eastern Pacific, 19 July 2007, sea cave. Length: 8 mm. Photographer: Ali Hermosillo.



Hermosillo, A, 2008 (Mar 13) Trapania darwini? from the tropical eastern Pacific. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Ali,

This message is a little dated as you sent it last year and I have just retrieved from the backlog since Trapania are the 'flavour of the week'.

I assume this is the new Trapania darwini but would like some confirmation please.

Best wishes,
Bill Rudman

Rudman, W.B., 2008 (Mar 13). Comment on Trapania darwini? from the tropical eastern Pacific by Alicia Hermosillo. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from