Halgerda formosa     Bergh, 1880
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This species has been observed on Reunion, Mauritius, Mayotte and Madagascar Islands


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

Halgerda formosa
Showing species characteristics...

Photo Philibert Bidgrain
Reunion, Etang salé les bains, 25 October 2005, size 15-18 mm

See more about : Sightening and mating periods

See more about : Halgerda formosa variability in Southwest Indian ocean

Remarks :

Identification confirmed by Hsini Lin, Bill Rudman and Nathalie Yonow
    Synonymous : (according Worms)
          - No other name

Bibliographic data :

This species was previously identified with H. punctata , a species described from Ceylon as whitish-grey, rather translucent with yellow papillae on mantle, and purple spots on foot and a few also on mantle (Rudman, 1978 - Zanzibar, Gosliner, 1987 - South Africa).
    However Fahey & Gosliner (1999) have concluded that the species illustrated here is H. formosa (Bergh, 1880). One external difference is that while H. formosa has distinct low ridges lined with yellow or orange, in H. punctata the ridges are indistinct and there are yellow tubercles.
    A similarly coloured species is H. toliara which can be distinguished as follows:

H. formosa (Bergh, 1880)
- Some black spotting around mantle skirt
- The rhinophore club is black and the white stalk has a black line up the posterior midline
- The gills have a black line running along the inside upper edge
    H. toliara (Fahey & Gosliner, 1999).
- No black spots on mantle,
- There is no black line on the rhinophore stalk
- The distal half of each gill seems to be all black

    The pattern of the dorsal ridge is very variable in Reunion Island. (for more details, see Yves Coze photos (January 2004) in Bill Rudman Seaslug site.

Material examined by Nathalie Yonow ( see reference/publications).

One specimen collected from grand Baie (Mauritius), 5 March 1990, size : 13 mm.

References :

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

Publications :

Fahey, S. & Gosliner, T.M. (1999) description of three new species of Halgerda from the western Indian ocean, with a redescription of Halgerda formosa , Bergh, 1880. Proceedings of the California Academy of Sciences, 51(8) : 365-383.
    Fahey, S.J. & Gosliner, T.M. (2001) On the genus Halgerda (Nudibranchia: Halgerdidae) from Western Australia with descriptions of four new species. Bollettino Malacologico, 37(5-8) : 55-76.
    Rudman, W.B. (1978) The dorid opisthobranch genera Halgerda and Sclerodoris from the Indo-West Pacific. Zoological Journal of the Linnean Society 62 : 59-88.
    Yonow, N. and Hayward , P. J. (1991). Opistobranches de l'île Maurice, avec la description de deux espèces nouvelles (Mollusca : Opistobranchia) Revue française d'aquariologie herpétologie, 18 (1), 1-30

Other photos of Halgerda formosa :


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.

Halgerda formosa


Halgerda formosa E.Eby

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

halgerda formosa


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


 More photos from Indian Ocean

See more about : Halgerda formosa variability in Southwest Indian ocean

Mauritius, Halgerda formosa, at Pereybère, by Marina Poddubetskaia.

Reunion, Halgerda formosa, at Mare de Baramine, by Maurice Jay

Mauritius, Halgerda formosa, at Pereybere, by Mathieu Bayon

Reunion, meeting between H. formosa and P. meandrina, at Saint Paul, by Guillaume Boeye 

Reunion, H. formosa juvenile pattern (?), at Etang salé, by Hugues Flodrops

Reunion, Halgerda formosa, at Saint Paul, by Christophe Cadet

Reunion, juvenile pattern (?) of H. formosa, at Saint Paul, by Sully Bachel 

Reunion, Halgerda formosa mating, at Etang salé, by Hugues Flodrops 

Mayotte, Halgerda formosa, at N'Gouja, by Sylvain Le Bris

Reunion, Halgerda formosa, at Etang salé, by Raphaël Roland Gosselin