Rostanga orientalis
Rudman & Avern, 1989
Order: NUDIBRANCHIA
Suborder: DORIDINA
Superfamily: EUDORIDOIDEA
Family: Dorididae
DISTRIBUTION
Known at present from Japan and China.
PHOTO
Hoi Ha (Flynn Pt.), Hong Kong; 1-4m, (27 mm long preserved), 18 April 1983, AM C139144. Photos: Brian Darvell.
See also R. orientalis - Radula.
The colour photographs show the animal to be reddish orange with small scattered brown specks on the mantle epithelium. There are also scattered white specks mainly restricted to the tips of the caryophyllidia. The rhinophore stalk is transparent and the club is a translucent brown with some white edging to the vertical lamellae especially at the upper end. The stalked knob is white. The gills are translucent orange with some white speckling and a thin marginal or perhaps slightly sub-marginal white line at the tip of each gill. The animal is typical for the genus with the ovate mantle having a dense covering of caryophyllidia. The gills form an upright circle and each gill has a noticeably flattened tip. The rhinophore club consists of almost vertical lamellae and is surmounted by a stalked knob in the posterior mid-line. An egg mass, probably of this species, is illustrated by Abe (1964). It is a broad ribbon, somewhat sinuous along the free edge. This broad thin type of egg ribbon with apparently very small eggs is indicative of planktotrophic larvae.
Although some references to species of Rostanga from Japan refer to this species, the lack of anatomical detail, especially rhinophore and radular morphology, make identification difficult. The earliest record of R. orientalis from Japan is probably Eliot's record of R. muscula (1913), on the basis of radular morphology. Baba (1935) gives a good description of the radula and rhinophore morphology of this species (as R. muscula), and later references to R. arbutus (Baba, 1937, 1949; Abe, 1964) from Japan presumably refer to R. orientalis. There are no external features separating R. orientalis from other red species with vertical lamellae on the rhinophore. It differs from other described species of Rostanga in having a very elongate innermost lateral tooth with many short inner denticles and in having relatively large jaw plates. The name orientalis refers to its known distribution in Japan and China.
References:
• Rudman, W.B. & Avern, G.J. (1989). The genus Rostanga Bergh, 1879 (Nudibranchia:
Dorididae) in the Indo-West Pacific. Zoological Journal of the Linnean Society 96: 281-338.
Rudman, W.B., 2002 (February 4) Rostanga orientalis Rudman & Avern, 1989. [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/rostorie
Related messages
Rostanga orientalis from the Yellow Sea
August 19, 2006
From: Dong Bum Koh
Dear Bill,
Last weekend our DEPC (Digital Eco-Photo Club) members were toured in Yellow Sea.
We've got several photos from Tae An area.[126° E 36° 8'N] including this photo of Rostanga orientalis
Locality: Tae An area.[126° E 36° 8'N], -10m, South Korea, Yellow Sea, 5~6 August 2006. Photographer: Sung Soon Choi.
Best regards,
Dong Bum Koh
drkoh@seasee.co.kr
Koh, D.B., 2006 (Aug 19) Rostanga orientalis from the Yellow Sea. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/17434
Dear Koh,
The shape of the rhinophores and the 'furry' mantle certainly suggest this is a species of Rostanga, and it is most probably R. orientalis. However, at this stage of our knowledge it is always possible that there are more undescribed species of the genus. The only way to be sure is to study the radular morphology, the shape of the egg ribbon and identify their sponge prey.
Best wishes,
Bill Rudman
Rostanga orientalis from Hong Kong
February 8, 2002
From: Bill Rudman & Brian Darvell
Here is some information and photos on Rostanga orientalis from Brian Darvell's Hong Kong collections.
PHOTO:
UPPER: N. side of Gau Tau, Mirs Bay; 5-12 in, one specimen (19 mm long preserved), 11 April 1983, AM C139143. LOWER: Kai Kung Tau, Kat O Chan; 5-10 m, one specimen (6 mm long preserved), 15 April 1983, AM C139197. PHOTOS: Brian Darvell.
Hong Kong Collection Records:
(1) N. side of Gau Tau, Mirs Bay; 5-12 in, one specimen (19 mm long preserved), 11 April 1983, AM C139143. (2) Hoi Ha (Flynn Pt.); 1-4 in one specimen (27 mm long preserved), 18 April 1983, AM C139144. (3) Pak Ma Tsui; 7 in, one specimen (22 mm long preserved), 21 April 1983, HOLOTYPE, AM C151978. (4) Kai Kung Tau, Kat O Chan; 5-10 m, one specimen (6 mm long preserved), 15 April 1983, AM C139197.
Reference:
• Rudman, W.B. & Avern, G.J. (1989). The genus Rostanga Bergh, 1879 (Nudibranchia: Dorididae) in the Indo-West Pacific. Zoological Journal of the Linnean Society 96: 281-338.
Best wishes,
Bill Rudman & Brian Darvell
