Order : Nudibranchia
Suborder : Euctenidiacea
Superfamily : Doridoidea
Family : Discodorididae
Distribution : Western Indian Ocean
Maximal size : 30 mm
Abundance : Frequently on the fore reef zone and the rocky coast

Species characteristics :

Thin opaque white line at the mantle edge
   There are scattered rounded tubercles, joined by a network of yellow or orange-yellow ridges and a variable secondary reticulate pattern in "valleys"
   The rhinophores have a black club, and running up the posterior side stalk is a band of black.
   The sparse white gills have a black line running along the inside upper edge
   Few large rounded black spots on the mantle, usually at the posterior end behind the gills

Some author considered that the specimen with a unique large yellow ridge is a different species (Halgerda sp. 9 in NSSI) but In our region we found intermediate pattern between this kind of specimen and the classical pattern of this species, so I considered that it's just a variant of Halgerda formosa

Matthias Deuss

Mayotte, Passe Sada,
20 m, size : 20 mm

 The rhinophores have a black club, and running up the posterior side stalk is a band of black (a).

A unique large yellow ridge (b)

and some secondary yellow ridge (c) like in other specimens of this species

Florence Trentin

Mohéli, méa, 24 December 2004

 The rhinophores have a black club, and running up the posterior side stalk is a band of black (a).

A unique large yellow ridge (b)

In this photo you can observe a strange form of H. formosa : The abscence of the black's band on the posterior side of the rhinophore stalk and a black distal coloration of the gills. Perhaps it's a result of the small size of this animal (a juvenile pattern)
   This specimen appears to be very small (10 mm), perhaps the coloration on the posterior side of the rhinophores hasn't developed.
    We looking for such color variation in an adult specimen, so if you have taken a photo in Reunion Island, please Contact us..

Fabien Michenet

Reunion, "Cap la Houssaye", 10 m, size 10 mm, 15 August 2005

David Caron

Reunion, "Cap la Houssaye", at Saint Paul.

Mating between two specimens which have exactly the same pattern, while this species have a high degree of polymorphism.

Alain Puig

Reunion, Cap la Houssaye, 10 m, 23 November 2011

Mating between two specimens which have exactly the same pattern, while this species have a high degree of polymorphism.

Philibert Bidgrain

Reunion, Etang salé les bains, 13 October 2005, under less 1 m of water, size 25 mm

In this photo you can see the sparse white gills with a black line running along the inside upper edge

Richard Lai cheong

Mauritius, 21 June 2008

The foot border is pale yellow.

Philibert Bidgrain

Reunion, Etang salé, on the rocky coast, less 1 m, 5 November 2006, size : 25-30 mm.

The foot border is pale yellow.

Alain-Benoît rassat

Madagascar, Nosy Bé, banc louis, 14 m, 2012, size : 20 mm