Thorunna australis (Risbec, 1928)

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This species has been observed on Reunion, Mayotte and Madagascar Islands

Order : Nudibranchia
Suborder : Euctenidiacea
Superfamily : Doridoidea
Family : Chromodorididae
Distribution :New Caledonia and Christmas Island, Indian Ocean, Philippines, Marshall islands and Japan.
Maximal size : 15 mm
Abundance : Seldom if ever...

Species characteristics :

The mantle is a uniform translucent orange-pink.
   At the posterior and anterior ends of the mantle there is a number of large diffuse purple spots interspersed with small white specks forming an arc arc on the inside edge
    On each side of the mantle from along side the rhinophores there is a thin opaque white line which runs back to just behind the gill pocket, and on the outside of each of these lines are purple-red spots forming a submarginal row.
   The rhinophore and the gills are white with an orange-red band across the middle.

thorunna australis
Showing species characteristics...
Photo Matthias Deuss
Mayotte, Bandrélé, 2 m, 22 December 2009, size : 10 mm

See more about : Sightening and mating periods

Remarks :

Identification confirmed by Bill Rudman and Nathalie Yonow
    Like other specimens (see Bill Rudman Sea Slug forum or Gosliner in Indo-Pacific nudinbranchs) our specimen has a thin marginal white band.
    In Nudipixel and in Nudibranchs of the World (Debelius) you can found a "different pattern" for this species....
    Synonymous : (according Worms)
          - Chromodoris australis, Risbec, 1928
          - Glossodoris australis, (Risbec, 1928)

Bibliographic data :

The mantle is a uniforme translucent orange-pink, except at the anterior and posterior ends , where the epidermis is much more transparent and milky orange mantle glands can be seen
    The rhinophore stalk is transparent and the club is white with an orange-red band across the middle.
    The six gills are white with a median orange-red band. They are simple forming a circle, open posteriorly, around the anal papilla.

The foot is translucent pinkish-purple with a few reddish purple spots and a broken white medium line at the posterior end. It is very elongate and it extends some distance beyong the posterior end of the mantle when the animal is crawling
    The oral tentacles are pinkish.
    This species inhabits shallow patch reefs and is found beneath coral rubble.
    Thorunna australis is rather similar in colour to Hypselodoris maculosa but :
            - Hypselodoris maculosa has multiple longitudinal white lines on the mantle and T. australis has only one longitudinal white line on either side of the mantle.

References :

Bill Rudman Seaslug site : Sea Slug Forum : Thorunna australis
   Nudipixel Thorunna australis!!!

Publications :

Johnson R.F. & Gosliner T.M. (2012) Traditional taxonomic groupings mask evolutionary history: A molecular phylogeny and new classification of the chromodorid nudibranchs. PLoS ONE 7(4): e33479
    Risbec, J., 1928a. Contribution à l'étude des nudibranches Néo-Calédoniens. Faune des Colonies Françaises, 2 : 1-328.
    Rudman, W.B. (1986) The Chromodorididae (Opisthobranchia: Mollusca) of the Indo-West Pacific: Noumea purpurea and Chromodoris decora colour groups. Zoological Journal of the Linnean Society 86(4) : 309-353.

Other photos of Thorunna australis :

Alain-Benoît Rassat


Madagascar, Nosy Bé, 3 August 2016




Maurice Jay

Réunion, an old photo...



thorunna australis M.Jay

 More photos from Indian Ocean

If you have taken a photo of this species in Reunion Island, please Contact us...