Re: Colour form of Cuthona yamasui

February 22, 2008
From: Samson Tan

Concerning message #21277:

Hi Bill
This animal you have identified as a variation of Cuthona yamasui looks very close to the animal in the enclosed photos. I saw this slug during my last diving trip at Bali on 25th October 2007. It looks similiar to Phidiana sp. However, it does not match 100% the characteristic of Phidiana militaris, P. indica or P. hiltoni.

Locality: Seraya coast, near Tulamben, 12 metres, Bali, Indonesia, Lombok Straits, 25 October 2007, rocky shore, volcanic sendiments. Length: 60 mm. Photographer: Samson Tan.

Samson Tan

Tan, S., 2008 (Feb 22) Re: Colour form of Cuthona yamasui. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Samson,

It certainly has similarities in general colour but your differs in a number of features. Firstly the cerata in Cuthona yamasui are ranged in regularly spaced rows and each ceras is about the same size. In your animal the rows of cerata are clumped into groups with spaces in between each group. Also in each group the cerata vary greatly in size, being very small near the outside and long and recurved in the inside of each row. Your animal is indeed a phidianid, as you suspected, and almost certainly a colour form of Moridilla brockii

Best wishes,
Bill Rudman

Rudman, W.B., 2008 (Feb 22). Comment on Re: Colour form of Cuthona yamasui by Samson Tan. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from


Moridilla brockii

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