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

Order : Nudibranchia Suborder : Euctenidiacea Superfamily : Polyceroidea Family : Hexabranchidae Distribution : Tropical Indo-West Pacific. Maximal size : 400 mm Abundance : From time to time on the fore reef zone and frequently on the rocky coast Species characteristics : Six- branched gills are inserted separately into the body wall within distinct pockets Variable in color, but always contain shades of red, pink or orange The oral tentacles have a hand-like appearance, they are divided into a pair of fingered (digitate) lobes. It can swim with the characteristic dorso-ventral muscle waves along the body.
	Showing species characteristics...	Photo Philibert Bidgrain The "mottled form": Reunion, Etang salé les bains, on a rocky coast, 05 January 2005, size : 35 mm

Florence Trentin The yellow/orange form when dancing, like a "Spanish dancer " during the night. Reunion,

Thierry Peres The Red form looks like Red sea specimens. Reunion, Cap la Houssaye, Saint Paul, 23 April 2009, size : 110 mm

See more about : Sightening and mating periods
   See more about : H. sanguineus, from juvenile to sub-adult form
   See more about : Detail from H. sanguineus ; rhinophores, gills, oral tentacles
   See more about : Hexabranchus excretion
   See more about : Hexabranchus sanguineus variability in Southwest Indian ocean
   See more about : Commensalism between a shrimp and Hexabranchus sanguineus
   See more about : Hexabranchus swim like a spanish dancer...
   See more about : The Juvenile of Hexabranchus sanguineus is able to swim...

Remarks :

Identification confirmed by Bill Rudman
    Synonymous : (according Worms)
               - Very numerous synonymous, see worms

Bibliographic data :

The species was first described from the Red Sea and based on a red colour form. The mottled form is the most common colour form, although yellow/orange animals have been reported from Hawaii and from Tanzania.
    There exist in Reunion island the mottled form (upper photo), the yellow/orange form (upper photo) and the red form (upper photo)
    H. sanguineus can be found in tropical waters worldwide from the intertidal to quite deep water - deeper than scuba divers can safely venture.
    The rhinophores have a smooth stalk and enlarged upper section like a club (clavus) bearing numerous lamellate. The rhinophores are orange to red-orange with white stripes along the outer faces of the lamellae.
    Juveniles of Hexabranchus which looks quite different from the adults, and is unable to swim
    H.sanguineus has an elaborate behavioral repertoire. Animals usually curl the lateral areas of the mantle inwards leaving only the central section of the dorsum exposed.
      Once irritated, they rapidly unfurl these areas to expose the striking red and white pattern beneath. This is a good example of defense through startling display.
      With continued irritation, animals raise the mantle edges and commence swimming. During swimming, the whole body is arched dorso-laterally and waves pass along the mantle in synchrony with the movements of the foot.
    It is a sponge-feeder but does not seem to be a specialised feeder on a particular species of sponge. The skeletal spicules of many encrusting sponges have been found in its stomach.
    Like many nudibranches, H.sanguineus seems to be protected somehow from fish predation. The bright red colour on their mantle has long been considered a 'warning' colouration to fish. In the last ten years or so we now have evidence to show that H.sanguineus has distasteful, and potentially toxic, chemicals in its body and egg masses. These chemical molecules (macrolides) are almost identical to antifeedant chemicals found in Halichondria, one of the sponges that H.sanguineus eats. The sponge produces the molecules to protect itself from fish predation. It is thought that H.sanguineus obtains the molecules from the sponge during feeding, and after modifying the structure of the molecule slightly, stores them in its skin and egg masses for its own protection.
    The bright red egg ribbons are quite characteristic.
    If you are lucky, you can observe around the gills, a commensal shrimp, Periclimenes imperator

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

One specimen collected from Tamarin (Mauritius), 17 October 1985, size : 21 mm.

References :

Bill Rudman Seaslug site : Sea Slug Forum : Hexabranchus sanguineus
   Nudipixel : Nudipixel : Hexabranchus sanguineus

Publications :

Double,T (1992) Here be giants. BBC Wildlife 10(5, May), 34-40.
    Edmunds,M (1968) On the swimming and defensive response of Hexabranchus marginatus (Mollusca, Nudibranchia). Journal of the Linnean Society, (Zoology) 47(313) : 425-429.
    Francis,MP (1980) Habitat, food and reproductive activity of the nudibranch Hexabranchus sanguineus on Tongatapu Island. The Veliger 22(3) : 252-258. (Figs 1-4)
    Gohar,HAF; Soliman,GN (1963) The biology and development of Hexabranchus sanguineus (Ruppell & Leuckart) (Gastropoda, Nudibranchiata). Publications of the Marine Biological Station, Al-Ghardaqa, Egypt, 12 : 219-247. (Pls.l-2)
    Pawlik,JR; Kernan,MR; Molinski,TF; Harper,MK; Faulkner,DJ (1988) Defensive chemicals of the spanish dancer nudibranch Hexabranchus sanguineus and its egg ribbons: macrolides derived from a sponge diet. Journal of Experimental Marine Biology and Ecology, 119 : 99-109.
    Roesener,JA; Scheuer,PJ (1986): Ulapualide A and B, extraordinary antitumor macrolides from nudibranch eggmasses. Journal of the American Chemical Society, 108 : 846-847.
    Thompson,TE (1972): Observations on Hexabranchus from the Australian Great Barrier Reef (Gastropoda: Opisthobranchia). The Veliger, 15(1) : 1-5.
    Young,DK (1969) The functional morphology of the feeding apparatus of some Indo-West Pacific dorid nudibranchs. Malacologia, 9(2) : 421-446.
    Kernan,MR; Faulkner,DJ (1987) Halichondramide, an antifungal macrolide frim the sponge Halichondria sp. Tetrahedron Letters, 28: 2809-2812.

Other photos of Hexabranchus sanguineus :

Philibert Bidgrain Reunion, Trois Bassins, Souris Blanche on the rocky coast, less 1 m, 14 March 2010, size : 10-12 mm Branched gills are inserted separately (a) into the body wall within distinct pockets A small specimen with the juvenile pattern

Philibert Bidgrain Reunion, Trois bassins, on a rocky coast, 8 January 2007, size : 100-125 mm   Crawling on a Protopalythoa sp

Philibert Bidgrain Reunion, Etang salé les bains, on a rocky coast, 27 November 2006, size 200-220 mm A large specimen (mottled form) with vivid coloration.

Maurice Jay Reunion, A fairly red "mottled form"

Philibert Bidgrain The "Mottled form": Reunion, Etang salé les bains, on a rocky coast, 100 mm, 05 January 2005. A mottled form with pale coloration

Florence Trentin Reunion, The yellow/orange form when not dancing.

Philibert Bidgrain The "mottled form": Reunion, Etang salé les bains, on a rocky coast, 80-100 mm, 23 October 2006   Once irritated, they rapidly unfurl these areas to expose the striking red and white pattern beneath.

Sylvain Le Bris Mayotte, 6 December 2008 a very small specimen According Bill Rudman : " There is no easy way to distinguish it externally as a Hexabranchus at this small size because the characteristic oral lobes and separate gills are not clear at this early stage of its growth."

Laurent Beche Reunion, Etang salé lagoon, less 1 m, August 2008, size : 50-60 mm, During the night. A depigmented yellow/orange form

Jean bernard Galves Madagascar, 20 m, September 2008, size : 700 mm According Jean bernard Galves this kind of large specimen was observed in Madagascar, Mayotte and Reunion Islands . Large specimen of Hexabranchus sanguineus ???

Jean-Luc Cheverry Reunion, Saint Pierre lagoon, less 1 m, 13 August 2012, size : 30 mm   During the night. A small yellow/orange form

See more about : Hexabranchus sanguineus, from juvenile to sub-adult form
   See more about : Detail from Hexabranchus sanguineus ; rhinophores, gills, oral tentacles
   See more about : Hexabranchus excretion
   See more about : Hexabranchus sanguineus variability in Southwest Indian ocean
   See more about : Commensalism between a shrimp and Hexabranchus sanguineus
   See more about : Hexabranchus swim like a spanish dancer...
   See more about : The Juvenile of Hexabranchus sanguineus is able to swim...
    Reunion, Hexabranchus sanguineus, a juvenile form at Saint Gilles, by Maurice Jay
    Mauritius, Hexabranchus sanguineus mottled form, at Pereybère, by Marina Poddubetskaia
    Reunion, dance with Hexabranchus sanguineus, at Etang Sale, by Hugues Flodrops  
    Reunion, gills detail of H. sanguineus, at Saint Leu, by Guillaume Boeye
    Reunion, Hexabranchus sanguineus mottled form, at Etang salé, by Mathieu Lagarde  
    Reunion, Berthellina sp and Hexabranchus sanguineus, at Etang salé, by Philibert Bidgrain 
    Mayotte, a fairly red mottled form of Hexabranchus sanguineus, at Petite-Terre, by Norbert Verneau 
    Mauritius, Hexabranchus sanguineus mottled form, at Pointe d'esni, by David Caron
    Mayotte, a giant Hexabranchus sanguineus, at Sada, by Florence Trentin 
    Reunion, Juvenile of Hexabranchus sanguineus, by Sully Bachel
   Reunion, Hexabranchus sanguineus, swim with fishes, at Etang salé, by Philibert Bidgrain
   Reunion, gills detail of Hexabranchus sanguineus, at Etang salé, by Christophe Cadet
   Reunion, juvenile form of Hexabranchus sanguineus, at Saint Gilles, by Philibert Bidgrain
   Reunion, Hexabranchus sanguineus swim under the surface, at Saint Pierre, by Nathalie Rodrigues
   Rodrigues, Hexabranchus sanguineus mottled form, by Rachel Lebatard
   Madagascar, Hexabranchus sanguineus yellow/orange form, by Michel Touzet
   Reunion, Hexabranchus sanguineus smilling for the photograph, at Saint Gilles, by Philippe Bourgeon
   Seychelles, a fairly red "mottled form" of Hexabranchus sanguineus, by Christophe Mason-Parker