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This species has been observed on Reunion

Order : Nudibranchia Suborder : Dexiarchia Superfamily : Tritonioidea Family : Phylliroidae Distribution : Circum tropical. Maximal size : 55 mm Abundance : Species characteristics : The body of this flattened pelagic mollusc is laterally compressed, elongate and fish or leaf like. It is perfectly transparent. The digestive gland, and other organs are seen through the skin. There is one pair of developed rhinophores.
	Showing species characteristics...	Photo Alain Diringer Reunion, Cap la Houssaye, 8 November 2013, size : 50 mm

See more about : Sightening and mating periods

Remarks :

Identification confirmed by Nathalie Yonow
   Around the world there are two different species of Phylliroe but it is unclear whether these two species are distinct. According differents authors we can found theses differences :
           - It seems that one difference is that P. lichtensteiniii have 3 ovotestis lobes and P. bucephala has only two.
           - The digestive gland has no constriction in the middle (Phylliroe lichtensteinii) and a 'X'-shaped digestive gland (P. bucephala)
           - In P. buceplala the tail is long, more than 16% of the body length and in P. lichtensteinii the tail is short, less than 16% of the body length.
           - In P. buceplala there is one pair of well developed rhinophores while in P. lichtensteinii there is one pair of relatively small rhinophores
So I called this species Phylliroe sp1

Synonymous : (According Worms)

Phylliroe bucephala Lamarck, 1816            - Phylliroe bucephalum Lamarck, 1816            - Phylliroe roseum d'Orbigny, 1836

Phylliroe lichtensteinii Eschscholtz, 1825             - Phylliroe atlantica Bergh, 1871

Bibliographic data :

The foot is reduced to a pedal gland not disturbing the body outline
    The head, before the rhinophores, is downward directed with a terminal mouth.
    The anus is situated on the right lateral side in the centre of the body
    The digestive gland, and other organs are seen through the skin.
    This epipelagic species is highly bioluminescent and emits flashes of light when disturbed.
    Juveniles of Phylliroe are found exclusively feeding on the bell of the hydromedusa Zanclea costata. At first the nudibranch is attached to the inside of the bell of the meduse with its very small foot. It sucks tissue from the ring, radial canals and manubrium of the meduse and grows from 1.6 mm to 11 mm in just ten days, while the meduse shrinks. When the slug is as big as the meduse, it starts to swim, eating the remaining parts, including the tentacles.
       In adulthood its diet is no longer restricted to Zanclea, although observations of feeding behaviour are sparse. Phylliroe has been seen approaching a swarm of the larvacean Oikopleura albicans from below, grabbing a specimen with its paired denticulate jaws and swallowing it in half a minute. Adults have also been observed to prey on the meduse Aequorea
    It lives in the upper water layers of warm waters in all oceans

References :

Bill Rudman Seaslug site : Sea Slug Forum : Phylliroe bucephalum and Phylliroe lichtensteini

Publications :

Eschscholtz, J.F. von (1825). Bericht über die zoologische Ausbeute der Reise von Kronstadt bis St. Peter-und Paul. Isis von Oken, 16(section 1, part 6) : 734-738, pl. 5
    Lalli, C.M. & Gilmer, R.W. (1989). Pelagic Snails. The biology of holoplanktonic gastropod mollusks . Stanford: Stanford University Press.
    Odhner, N. H. 1936. Nudibranchia Dendronotacea -- A revision of the system. Memoires du Musee Royal d'Histoire Naturelle de Belgique, series 2, fasc. 3 : pp. 1057-1128, pl. 1.
    Pruvot-Fol, A. 1946. Revision de la famille des Phylliroidae (Phyllirhoidae)Bergh. Bulletin du Museum National d'Histoire Naturelle, Paris, series 2, 18(2) : 172-178.
    Ralph, P. M. 1959. Notes on an abnormality in the liver caeca of the nudibranch Phylliroe lichtensteini Eschscholtz, 1825. Proceedings of the Malacological Society of London, 33 : 186-192.

Other photos of Phylliroe sp1 :

Alain Diringer Reunion, Cap la Houssaye, 8 November 2013, size : 50 mm (a) Buccal mass (b) Stomach (c) Digestive gland (d) Reproductive organs (e) Anus The body of this flattened pelagic mollusc is laterally compressed, elongate and leaf or fish like

Nicole Gravier-Bonnet Reunion, 19 februay 2006 (a) Buccal mass (b) Stomach (c) Digestive gland Juveniles of Phylliroe are found exclusively feeding on the bell of the hydromedusa Zanclea costata(d)

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