Phestilla melanobrachia? from sthn Queensland [1]

December 17, 2008
From: Gary Cobb

Hi Bill and everyone!

During our dives which happen almost every weekend we find many species of Opisthobranchs. One beautiful we see here is Phestilla melanobrachia. The orange and black colourforms. They are always found on Tubastrea sp. (daffodil or sunshine coral) it's food source. We sometimes find it on the substrate below overhangs were the coral lives. Where we think it has been knocked off. We also found the two colour forms on the same coral! One coral group yielded 4 animals, 3 orange and one black. On collecting them for study and taxonomic photos we noticed they love to trail each other! The largest one always in the front.

Locality: Mooloolaba, Sunshine Coast, 16m, Queensland, Australia, Pacific Ocean, 26 April 2008, Subtidal. Length: 10-30mm. Photographer: Gary Cobb and David Mullins.


Cobb, G.C., 2008 (Dec 17) Phestilla melanobrachia? from sthn Queensland [1]. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Gary,

Thanks for these observations and photos. Interestingly, I list two papers by Larry Harris on the species' Fact Sheet where he describes the behaviour of this species in Singapore and how they are usually found on broken off - but still live - pieces of Tubastrea found in the sand beneath overhanging colonies, exactly as you describe from sthn Queensland.

I would be interested in more observations on the colour forms and the corals they are living on. I have always assumed the colour forms would be found on corals of a matching colour, as the colour of the digestive gland is rather dependent on the food colour. If your animals are living on broken off fragments perhaps this means they have to change from one fragment to another as they eat it clean. If so, perhaps they change colour as they eat from a new fragment of a different colour. It would be interesting to hear of your observations on this point. Perhaps you have seen animals in the process of going from yellow to black or vice versa? Thanks also for the photos in your accompanying message [#22017].

Best wishes,
Bill Rudman

Rudman, W.B., 2008 (Dec 17). Comment on Phestilla melanobrachia? from sthn Queensland [1] by Gary Cobb. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

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