May 23, 2007
From: Richard Swann
Concerning message #13700:
I found it strange that they were, when I first found them, in the mating position and would have said they were in the act. If they are different species do you have any knowledge of this being possible? I did consider that they could be feeding and not mating at all but no eggs seem to be present.
Locality: Sulug island, Kota Kinabalu, 23meters, Sabah, Borneo, South China Sea, 16 April 2007, Reef slope, outreef. Length: Around 5mm. Photographer: Richard Swann.
I also found the pink tips unusual. if they are not mating then they must be very good friends !
As always i look forward to hearing your thoughts.
email@example.comSwann, R., 2007 (May 23) Colour forms of Favorinus tsuruganus ?. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/19909
Certainly the yellow and black animal is Favorinus tsuruganus but the one with the purplish tips is rather unusual. It is quite similar in colour to an animal I have identified as Favorinus pacificus, but that species has smooth rhinophores. Favorinus mirabilis is also similar in colour but always has a dark spot near the ceratal tip and its rhinophores have many more leaves.
Typical Favorinus tsuruganus has three quite unusual cup-shaped processes on each rhinophore, which is a very distinguishing feature. I have looked carefully at the rhinophores of the purple-tipped animal and although they are not black, there do seem to be three very similarly shaped cup-shaped structures there as well. I know of no other species of Favorinus with similar structures, so your observation that they appear to be mating would suggest that this is a colour form of F. tsuruganus which has never been reported before. Which makes it a very interesting find.
One problem - and there are often problems unfortunately - is the identity of Favorinus tsuruganus. All authors accept it is the yellow animal with black-tipped cerata, and black rhinophores with these 3 cup-shaped structures. This is certainly the animal illustrated and described by Baba & Abe in 1975. However in that paper they note that the animal on which the species is based (Baba & Abe, 1964) didn't have these 3 cup-shaped structures on the rhinophores. It just had two rounded swellings. Either they made a mistake in their first description, or perhaps they had a damaged animal which had not regrown the rhinophores very well. Perhaps I shouldn't have mentioned it, but it does mean the identity of F. tsuruganus is still a little unstable.
Baba, K. & Abe, T. (1964) Record of Favorinus tsuruganus n. sp., from Tsuruga Bay, Japan (Nudibranchia - Eolidoidea). Publications of the Seto Marine Biological Laboratory, 12(2): 163-164.
Baba, K. & Abe, T. (1975) Comments on further specimens of Favorinus tsuruganus Baba & Abe from Echizen-cho near Tsuruga Bay, Japan (Nudibranchia: Eolidoidea: Favorinidae). Publications of the Seto Marine Biological Laboratory, 22(1-4): 117-120.
Re: Colour forms of Favorinus tsuruganus
From: Colin Ogden, June 27, 2007
Favorinus tsuruganus from Sydney Harbour
From: Nicholas Missenden, May 27, 2005
Favorinus tsuruganus in the Red Sea
From: Jacob Dafni, April 25, 2005
Favorinus tsuruganus from Reunion Island
From: Philibert Bidgrain, February 22, 2005
Favorinus tsuruganus on Goniodoris felis eggs
From: Dong Bum Koh, February 7, 2005
Favorinus tsuruganus from Sth Korea
From: Dong Bum Koh, December 19, 2003
Favorinus tsuruganus eating Hexabranchus eggs
From: Yves Coze, December 1, 2003
Favorinus tsuruganus from Korea
From: Dong Bum Koh, November 15, 2003
Favorinus tsuruganus - egg-laying observations
From: Jim Black, August 20, 2003
Nembrotha rutilans & Favorinus tsuruganus
From: Mark Burnett, December 30, 2002
Favorinus tsuruganus - feeding on eggs
From: Dave Harasti, December 8, 2002
Favorinus tsuruganus from Indonesia
From: Ginette Allard, November 27, 2002
Favorinus tsuruganus - new record from N.Z.
From: Gareth Jones, February 14, 2002
Re: Egg eater from Japan
From: Nishina Masayoshi, August 5, 2001
Egg eater from Japan
From: Nishina Masayoshi, July 30, 2001
Re: Colour of Favorinus tsuruganus
From: Stuart Hutchison, June 4, 2001
Favorinus tsuruganus from Indonesia
From: Stuart Hutchison, June 3, 2001
Photo of Favorinus tsuruganus
From: Lindsay Warren, March 19, 1999