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

Order : Nudibranchia Suborder : Euctenidiacea Superfamily : Doridoidea Family : Discodorididae Distribution : Tropical Indo-West Pacific Maximal size : 150 mm Abundance : From time to time on the fore reef zone Species characteristics : The rhinophores are uniformly red, with the tips somewhat lighter.     There are numerous small, light brown red dots covering the dorsum, large pale cream irregular, ramified areas and large, rounded or oval dark red blotches randomly distributed on the dorsum. Some specimens appear reddish overall     Like other Platydoris the mantle's surface is smooth but sandpaper rough to the touch
	Showing species characteristics...	Photo Jean Cardon Reunion, "Petit Canyon" at Saint Gilles during a night dive

See more about : Sightening and mating periods

Remarks :

Identification confirmed by Angel Valdès Hsini Lin and Terry Gosliner
    Synonymous : (according Worms)
          - Doris formosa, Alder & Hancock, 1864

Bibliographic data :

This species, with P. striata, P. scabra, P. cruenta and P. cinerobranchia form a group of very similar species.

Remark : Dorgan, K.M., A. Valdés & T.M. Gosliner. 2002 consider that P. cruenta ( Quoy & Gaimard, 1832 ) and P. striata (Kelaart, 1858) are regarded as synonyms.

	P. formosa	P. scabra	P.cruenta	P. striata	P.cinerobranchiata
Localisation	Tropical Indo-West Pacific	Tropical Indo-West Pacific	Tropical West Pacific	Tropical Indo-West Pacific	Solomon Islands
Mantle coloration	Brown spotted with red patches	Brown spotted without red patches	Brown lined with red patches	Brown lined without red patches	Reddish, or orange patches and no brown specks or lines.
Rhinophore coloration	They are uniformly red, with the tips somewhat lighter	They are yellowish, often with darker orange tips.	They have a dark brown clavus with white flecks on the lamellae	They are dark red or brown	They are dark red or brown
Underside of the mantle and foot	The underside is white and has many large, bright orange red spots (not always easily visible). These spots are larger and densely concentrated near the foot, where some of them can be fused together	The underside of the mantle is dirty white and there are some brown speckles on the side of the foot.	The underside of the mantle is white with brown lines near the foot, and scattered red patches. The sole of the foot can also have brown lines	The underside of the mantle is white without red patches	The underside of the mantle is white with red patches

The body feels very firm because the skin is toughened with tiny rods ( the dorsum is entirely covered with small caryophyllidia ) and the mantle is extremely rough to the touch.
    The rhinophoral and branchial sheaths are elevated and whitish, with irregular dark brown spots. The branchial sheath has six branchial lobes, with the anterior and posterior ones being larger than the others.
    The perfoliate rhinophores always have 37 lamellae
    The ventral side is white and has many large, bright orange red spots. These spots are larger and densely concentrated near the foot, where some of them can be fused together. There are also very small, dark brown to black spots on and around the foot.
    The six large compound gills which form a complete circle around the anus emerge from a deeply lobed branchial pocket. They are brownish with white tips.
    P. formosa is nocturnal and it probably feeds on siliceous sponges

References :

Bill Rudman Seaslug site : Sea Slug Forum : Platydoris formosa
   Nudipixel Platydoris formosa

Publications :

Alder, J. & Hancock, A. (1864). Notice of a collection of nudibranchiate mollusca made in India by Walter Elliot Esq., with descriptions of several new genera and species. Transactions of the Zoological Society of London , 5 : 113-147.
    Dorgan, K.M., A. Valdés & T.M. Gosliner. 2002. Phylogenetic systematics of the genus Platydoris (Mollusca, Nudibranchia, Doridoidea) with descriptions of six new species. Zoologica Scripta. 31(3): 271-319.

Other photos of Platydoris formosa :

Jean Cardon Reunion, "Petit Canyon" at Saint Gilles during a night dive Polymorphisme in P. formosa species. The rhinophores are uniformly red, with the tips somewhat lighter

Philippe Cao Van Reunion, Saint Leu, 24 March 2007, during a night dive, 15-18 m, size : 50-70 mm The rhinophoral and branchial sheaths are elevated and whitish, with irregular dark brown spots. The large gills emerge from a deeply lobed branchial pocket. They are brownish with white tips.

Hugues Flodrops Reunion, "Les kiosques" Saint-Leu, by night, 15 m, 30 January 2009, size : 130 mm The ventral side is white and has many large, bright orange red spots. These spots are larger and densely concentrated near the foot, where some of them can be fused together. In this specimen all the orange red spots fused and form a uniform orange red coloration. We need other photo to confirm this observation... There are also very small, dark brown to black spots on and around the foot.

Maurice Jay Reunion, "Pointe au sel" at Saint Leu, 45 m, 5 December 1987, size : 90-100 mm. Two specimens under a rock (mating behavior) The foot and the central area of the underside of the mantle are red.

Alain-Benoît Rassat Madagascar, Nosy Bé, 17 m, size : 120mm

Seychelles, Platydoris formosa, at Mahé, by Christophe Mason-Parker