April 7, 2010
From: Erwin Koehler
Concerning message #23331:
Mike has a nice video by John Greenamyer of it at
as Noumea sp.
Erwin@medslugs.deKoehler, E., 2010 (Apr 7) Re: Thorunna sp.? from the Andaman Sea. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/23441
Thanks for the link. I am afraid identifying small species of chromodorid to genus is very difficult without any information on their anatomy. If we are lucky and can see them, the position of the mantle glands can give us a clue. For example, in many species of Thorunna the mantle glands appear to be absent or invisible but in a few cases they follow the hypselodorid arrangement with a concentration of glands at the mantle edge behind the gills and a few at the anterior end of the body. Although I can't see the posterior glands in Lawrence Neal's photo, the posterior end of the mantle is constricted into shape suggestive of a gland mass. Similarly, I can see a couple of large white glands at the anterior end. Although not conclusive, my guess is that the mantle glands in this animal are hypselodorid in arrangement. In species of Noumea, the glands usually follow a chromodorid arrangement with a submarginal band of uniformly sized glands right around the mantle.
The other point I noticed was the orange 'crescent'-shaped mark at the anterior end of the mantle. At present the only animals I have seen with such a mark have been species of Thorunna.
I realise these are not very substantial features but if I have to choose between Thorunna and Noumea the little information I have all suggests Thorunna. But it is always possible it belongs to neither of these genera.