Rostanga? sp. 2
Hachijo Is. Japan, Length: 8mm. Depth: 5m
On rocky reefs in shallow water Photo: Rie Nakano.
Without some information on its anatomy it is not possible to say whether this is a species of Jorunna or Rostanga. See discussion and further photos in attached messages.Authorship details
Rudman, W.B., 2002 (January 17) Rostanga? sp. 2 [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/rostsp2
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.
email@example.comNakano, 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.
January 14, 2002
From: Rie Nakano
Is this a species of Rostanga?
In Hachijo Is. Japan, from November to January, we see this animal commonly.
On the rocky reef(shallow water)
firstname.lastname@example.orgNakano, R., 2002 (Jan 14) Rostanga? from Japan. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/5904
I am pretty sure that this is a species of Rostanga but it is difficult to identify them without looking at their anatomy. At present there are two species reported from Japan (Baba, 1991). One of these, R. orientalis, is orange-red and the other, R. risbeci, is black. However there are sure to be more species found there. One obvious difference is that your animal has horizontal lamellae on the rhinophores while R. orientalis has vertical lamellae. R. risbecia has horizontal lamellae, but it is black. If this animal is quite common perhaps you could take a photo of it on its sponge, and if you are lucky also photograph its egg ribbon.
• Baba, K. (1991) Review of the genus Rostanga of Japan with the description of a new species (Nudibranchia: Dorididae). Venus, The Japanese Journal of Malacology 50(1): 43-54. (Figs 1-5, Pl.1)