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This species has been observed on Mayotte and Madagascar Islands

Order : Cephalaspidea Superfamily : Philinoidea Family : Aglajidae Distribution : Tropical Indo-West Pacific Maximal size : 70 mm Abundance : (May) Seldom on the fore reef zone Species characteristics : It can be easily recognized by its black body with electric blue marginal and anterior mid-dorsal lines Posteriorly, the posterior shield extends into two long processes, the left one being one third longer than the right one
	Showing species characteristics...	Photo Sylvain Le Bris Mayotte, Nurserie, 10 m, 8 December 2008, size : 20 mm

See more about : Sightening and mating periods

Remarks :

Identification confirmed by Bill Rudman and Nathalie Yonow
    In Mayotte and Madagascar Islands we have an undescribed pattern for C. varians (or an other species....). Pattern in which the blue line at the edge of the parapodia and the posterior part of the body has been broken into a series of  streaks or dots...
    See Nudipixel or Rudman site for classical pattern.
    Synonymous : (according Worms)
               - Chelidonura velutina Berg, 1905

Bibliographic data :

It is pitch black with bright blue lines inside the edge of the parapodia, across the front of the head, inside the lateral edge of the extended head lobes, and medially on the head shield
    On the posterior shield, the processes are lined along both sides. One line form a U shape on the posterior dorsal shield and forms a midline on the outer edges of the “tails”. The second one runs along the inner surface of each tail, following the outer blue line.
    It presumably feeds on acoel flatworms
    Like other aglajid, the egg mass, when complete, is a sphere of jelly anchored in the sand with a long string of mucous. The string of eggs inside the jelly sphere forms a spiral.
    This species is often mistaken for the very similarly coloured Philinopsis gardineri but C. varians has long tapering "tails", the left one being one third longer than the right one

References :

Bill Rudman Seaslug site : Sea Slug Forum : Chelidonura varians
   Nudipixel Chelidonura varians

Publications :

Eliot, C.N.E., (1903). Notes on some new or little-known members of the Family Doridiidae. Proceedings of the Malacological Society of London, 5(5) : 331-7, Pl.13.
    Yonow, N. (1994) Opisthobranchs from the Maldive Islands, including descriptions of seven new species (Mollusca: Gastropoda). Revue fr. Aquariol., 20(4) : 97-130.
    Zamora-Silva A. & Malaquias M.A.E. (2017). Molecular phylogeny of the Aglajidae head-shield sea slugs (Heterobranchia: Cephalaspidea): new evolutionary lineages revealed and proposal of a new classification. Zoological Journal of the Linnean Society

Other photos of Chelidonura varians :

Sylvain Le Bris Mayotte, Nurserie, 10 m, 8 December 2008, size : 20 mm

It is pitch black with bright blue lines inside the edge of the parapodia (a) , across the front of the head (b), inside the lateral edge of the extended head lobes, and medially on the head shield (c) On the posterior shield, the processes are lined along both sides. One line form a U shape on the posterior dorsal shield (d) and forms a midline on the outer edges of the “tails”. The second one runs along the inner surface of each tail (e), following the outer blue line.

Fabrice Schubert Mayotte, Passe acoua, 10 m, 26 December 2009, size : 40-50 mm Quelques points remplacent des lignes bleues Some blue dots replace the blue lines The sensory bristles are clearly visible on the anterior edge of the head shield

Alain Benoît Rassat Madagascar, Nosy Bé, Anémone, 22 m , 3 May 2012, size : 80 mm   Fairly common in the same habitat on the same near coral boulders from 18 to 23 m) in April to May...