Costasiella sp. 1 from Sulawesi

July 28, 2000
From: Lindsay Warren

Dear Bill

This Costasiella was found by Rich Smith on 21 June 1999 at a depth of 7.1m on rubble on an underwater pinnacle next to Pulau Hoga  [Tukang Besi Archipelago, SE Sulawesi, Indonesia - Operation Wallacea].  Size: 3 mm.

Although similar to Costasiella sp. 1 he found in 1998 and which you posted on the Forum, there are several differences which may or may not be significant.  The first is that the rhinophores of this specimen narrowed down towards the end and were covered in colourful speckles whereas the 1998 specimen had rhinophores of the same diameter along their length and were entirely white.  The second difference is the black marking between and behind the rhinophores [see sketch at bottom left].  A third difference is that there were colourful specklings on the tail in this specimen and none on the 1998 one [see sketch at upper right] .  Illustrations: Rich Smith, Photo: Lindsay Warren.

Incidentally I noticed that the photo from 1998 was credited to me whereas it should in fact be credited to Adam Powell.

Do you think it is the same species or a different one?

All the best
Lindsay Warren

Warren, L., 2000 (Jul 28) Costasiella sp. 1 from Sulawesi. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Lindsay,
I think we are in trouble if those differences are significant. I am sure that your two animals fit within the normal range of variation to be found in that species. Clay Carlson & Patty Jo Hoff's animal is also probably the same species, which would suggest the black markings between the rhinophores are a quite important character. It is possible that some of the more brilliant iridescent speckling becomes less noticeable as the animals grow and/or become more pigmented.

I will change the photo credit.

Best wishes,
Bill Rudman.

Rudman, W.B., 2000 (Jul 28). Comment on Costasiella sp. 1 from Sulawesi by Lindsay Warren. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from


Costasiella sp. 1.

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