January 18, 2002
From: Rie Nakano
Thank you for your advice.
Here are some more photos of Rostanga from Hachijo Is. by Mr.Takasu in December,1998.
Depth is about 5m.
The sponge which it foods is pale purple, and its egg ribbon is creamy white.
firstname.lastname@example.orgNakano, R., 2002 (Jan 18) Rostanga sp. - more photos. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/6020
Thanks to you and Mr Takasu for the extra photos. Looking at them it seems this species ranges in colour form orange to almost black but it seems the balck colour is mainly in the microscopic spiculate tubercles (caryophyllidia) on its mantle. Fortunately Jun Imamoto has sent us excellent photos of an animal I think is Rostanga risbeci and if we compare that animal with yours we can see the rhinophores are quite different. In R. risbeci there is a large knob at the top of the rhinophore and the there are only a few lamellae. In your animal by comparison, the club gradually tapers to the tip, and there are many clsely spaced lamellae.
I suspect ypur animal may be a species of Jorunna rather than a Rostanga but we would need to know something about its anatomy. For convenience I will call it Ristanga? sp. 2 at present.