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This species has been observed on Reunion and Mayotte

Order : Nudibranchia Sous ordre : Euctenidiacea Super famille : Doridoidea Family : Chromodorididae Distribution : Indo West Pacific Maximal size : 20 mm Abundance : Seldom if ever on the reef flat zone and the rocky coast. Species characteristics : Translucent white body with characteristic broad white longitudinal lines the one along the midline often forming a “Y” just in front of the gills. These lines contain purple spots There are large purple and small spots scattered over the dorsum White edge mantle, followed by orange-brown The rhinophores are a translucent straw colour with an opaque white core and the simple gills are similary coloured.
	Showing species characteristics...	Photo Philibert Bidgrain Reunion, Etang salé on the rocky coast, less 1 m, 8 November 2005, size : 15-20 mm

See more about : Sightening and mating periods

Remarks :

Identification confirmed by Nathalie Yonow
    Synonymous : (according Worms)
          - Chromodoris decora, (Pease, 1860)
          - Doris decora, Pease, 1860
          - Glossodoris ndukuei, (Risbec, 1928)
          - Chromodoris ndukuei, Risbec, 1928
          - Glossodoris decora, (Pease, 1860)

Bibliographic data :

Mantle description :
          - The mantle is translucent with an orange band just in front of the edge.
          - There is a thin opaque white line which runs around the mantle and parallel to the edge, just encircling the rhinophores and gills pockets.
          - Between these intense white line and the orange border the mantle is pigmented white but not so intensely as the thin line
          - From between the rhinophores a thin line runs down the dorsal midline to midway where it bifurcates to form a loop around the gill pocket
          - Right at the edge the mantle is transparent, and the outer edge of the white mantle glands appear as a serie of white streaks or in some places a continuous white line
          - On the orange band is a line of small purple spots
          - Another row of much larger purple spots, diffuse at the edges, is found outside the thin white ring on the whitish submarginal band
   There is some variation in colour pattern :
          - Sometimes the purple spots on the orange border are few or absent.
          - Also, the region between the orange band and the white line encircling the gills and rhinophores varies from being as unpigmented as the central region to almost as heavily pigmented as the white line
          - In other specimens the Y-shaped white line and the encircling white line can be scattered with purple spots, and in others the Y-shaped line can be broken or have extra branches
   On the underside of the mantle the orange border is visible and at the junction of the mantle and the side of the body there is a row of small purple spots. Elsewhere the foot is white and translucent
   The egg mass is pale yellow.
   This species closely looks like Goniobranchus lekker, but G. lekker have opaque white spots on the dorsal surface of mantle (notum) and Goniobranchus decorus possesses a typical colour form with white Y-shaped pattern on the notum or purple spots in centre of back.
   Very similar is Goniobranchus setoensis which differs by having purple spots also in the greyish mid-dorsal region, and by having purple spots in the white 'Y".

References :

Bill Rudman Seaslug site : Sea Slug Forum : Chromodoris decora
   Nudipixel Chromodoris decora

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.
   Pease, W.H. (1860). Descriptions of new species of mollusca from the Sandwich Islands. Proceedings of the Zoological Society of London, 28 : 18-37
   Rudman, W.B. (1984) The Chromodorididae (Opisthobranchia: Mollusca) of the Indo-West Pacific: a review of the genera. Zoological Journal of the Linnean Society 81 : 115-273
   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 Goniobranchus decorus :

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