Favorinus sp. 2? from Madagascar

April 8, 2002
From: Lindsay Warren

Dear Bill
Another find during my recent trip to Madagascar was this Favorinus which looks very similar to Favorinus sp. 2 on the Forum from Okinawa although the ones I found do not feature white tips to the cerata. The other difference is that all their rhinophores were black / very dark purple when I found them and this did not change when I collected them to observe further.

I found them while diving at Charlie's Point, Ile Sakatia, NW Madagascar on 24 January 2002 at 11.45am at a depth of 40 ft. They were crawling over a small detached, dead branching coral covered in various benthic organisms such as filamentous algae, sponges, bryozoans but no sign of eggs of any
kind. There were 7 in all - 3 measuring 30 mm and the 4 smaller ones between 20-25 mm. A regular local diver said that whenever he had seen them they were always on Hexabranchus sanguineus eggs but there were none where I found them. Photos: Lindsay Warren.

I would be interested to know if you think these are the same as Favorinus sp. 2 although I realise that unless the internal anatomy is examined it would be impossible to know for certain.

All the best


Warren, L., 2002 (Apr 8) Favorinus sp. 2? from Madagascar. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/6220

Note added 26 July 2002: I think this is probably a colour form of Favorinus mirabilis and have moved messages concerning Favorinus sp. 2 and Favorinus sp. 6 to Favorinus cf. mirabilis page.

Dear Lindsay,
They certainly have similarities to Favorinus sp. 2. There is a problem with using colour to identify species of Favorinus because at least the ceratal component can change depending on the colour of the eggs they are eating. There are a number of species which have these distinctive black rhinophores with the 'cup-like' lamellae - Favorinus mirabilis, Favorinus sp. 2, and Favorinus tsuruganus.

Your animal differs from all of them in small colour details which are do not appear to be food related. One of these, F. tsuruganus, is reported on the Forum to eat Hexabranchus eggs, so it could be that species, without the black tips to the cerata, or it could be another species which also eats Hexabranchus eggs. The radula of species of Favorinus is very similar, and there is some evidence to suggest that denticles can be present or absent in the same species. I suspect we have a way to go before we can be confident with our taxonomy of this genus.

I think I will call this Favorinus sp. 6.
Best wishes,
Bill Rudman

Rudman, W.B., 2002 (Apr 8). Comment on Favorinus sp. 2? from Madagascar by Lindsay Warren. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/6220

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