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This species has been observed on Mayotte and Madagascar Islands

Order : Nudibranchia Suborder : Dexiarchia unassigned Cladobranchia... Family : Madrellidae Distribution : Indo West Pacific Maximal size : 45 mm Abundance : Seldom if ever on the reef flat zone Species characteristics : Body orange to reddish brown with opaque white pigment present between the rhinophores, on the rhinophoral stalk and on the cerata The brownish rhinophores are rather odd, elongated and pointed with a swollen area containing numerous papillae near the tip
	Showing species characteristics...	Photo Norbert Verneau Mayotte, Papani, on the reef crest, 5 August 2012, size : 15 mm

See more about : Sightening and mating periods

Remarks :

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

Bibliographic data :

The cerata are soft and elongated pointed at the tips and are arranged all around the outer half of the body, the middle is bare of cerata
    There can be speckles and patches of grey white elsewhere on the body and cerata.
    The underside of the foot is dark red.
    This species is known to feed on bryozoans, from which it obtains its pigment and upon which it is extremely well camouflaged. In all cases the background colour matches the bryozoan colonies on which they feed.
    These animals don't have defensive  cnidosacs, like the aeolids, but it is possible they have distasteful glandular secretions. They have a sac at the base of the papillae which can exude a yellowish secretion when they are disturbed. It seems to be based on waste from the digestive system and so is most probably from their bryozoan food. Again, we don't know if it has a defensive purpose.
    Very similar in shape to Madrella sanguinea but differs in localisation, coloration and size. M. sanguinea is seldom grows longer than 15 mm. Specimens from around southern Australia have a bright red or orange-red background colour (M. sanguinea) while specimens from tropical Australia and the Indo-West Pacific (M. ferruginosa) have an orange-brown, partially translucent colour.

References :

Bill Rudman Seaslug site : Sea Slug Forum : Madrella ferruginosa
   Nudipixel Madrella ferruginosa

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.

Other photos of Madrella ferruginosa :

Alain-Benoît Rassat Madagascar, Plateau des arches, 15 m, 29 September 2013, size : 40 mm Body orange to reddish brown with opaque white pigment present between the rhinophores, on the rhinophoral stalk and on the cerata The background colour matches the bryozoan colonies on which they feed.

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