Okenia rhinorma
Rudman, 2007

Suborder: DORIDINA
Family: Goniodorididae


Originally known only from western Indian Ocean (Tanzania, Red Sea), but records on the Forum from Indonesia, Japan, and Australia (Queensland, Victoria), suggest this species has a wide Indo-West Pacific distribution.


Upper Photo: Bongoyo Island, off Msasani Bay, Dar es Salaam, Tanzania. Coll: G.H. Brown, 7 November 1976. 11 mm long alive, AM C443912 [Holotype] Photo: Bill Rudman. Lower left: Yatush slope, Eilat, Israel, Gulf of Eilat, Red Sea, 29 m, on sea grass and patch reef, 16 March 2005, 1 specimen approx 15 mm long alive, [Photo: Binyamin & Shulamit Koretz]. Lower right: SEM of part of right side of radula. Scale = 10 µm. Photo: A. Miller.

The annimal is elongate and relatively high with the a distinct ridge running around the mantle edge between the six large lateral papillae. The rhinophores when fully extended are extremely long. The lamellae on the rhinophores are relatively small and form a band up each side.  There are approx 6 gills which are held erect and arranged in arch around the anus. 

The body is an opaque white with a pattern of translucent regions, and orange and purple patches or spots. The size and proportion of orange and purple patching varies in different animals. The lateral papillae are white with orange tips and subapical purple band while the rhinophores have a translucent white base, white anterior spots, mottled purple pigmentation down each side, and an orange tip. The gills are a translucent with brown and white pigmentation.

We know nothing of the biology of this species but it is similar in body shape and anatomy to the ascidian-feeding species from the North Atlantic which has been identified as Okenia aspersa, so I would not be surprised if it was an ascidian feeder as well.

  • Rudman, W.B. (2007) Two new species of Okenia (Gastropoda: Nudibranchia: Goniodorididae) from eastern Australia and Tanzania. Zootaxa, 1657: 57–67.

Authorship details
Rudman, W.B., 2007 (December 10) Okenia rhinorma Rudman, 2007. [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/factsheet/okenrhin

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