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This species has been observed on Reunion and Mayotte Islands

Order : Sacoglossa Superfamily : Limapontioidea Family : Caliphyllidae Distribution : Indo-West Pacific Maximal size : 40 mm Abundance : Seldom on the rocky coast and the reef flat zone Species characteristics : The back covered in leaf-like cerata contain fine branching digestive gland ducts. The rhinophores are long, forked (bifurcated) and transparent with a faint green pattern and small white pustules
	Showing species characteristics...	Photo Philibert Bidgrain Reunion, Etang salé les bains, 06 October 2005, size :15 mm

See more about : Sightening and mating periods
  

Remarks :

Identification confirmed by Nathalie Yonow
    Synonymous : (according Worms)
               - Phyllobranchillus orientalis (Kelaart, 1858)                    - Phyllobranchus orientalis (Kelaart, 1858)
               - Proctonotus orientalis Kelaart, 1858     

Bibliographic data :

The bases of the cerata are cylindrical and each unfurls to a flattened disc. Both faces of the cerata as well as their margins are covered with papillae.
    When disturbed this species is capable of casting off its cerata. This is a defensive strategy, called autotomy. New cerata grow back rapidly.
    This species has another defensive shield. The cerata and glands along the edge of the cerata produce sticky secretions. These milky secretions are distasteful, and function to repulse predators.
    P.orientalis is a sacoglossa and therefore feeds on algae. The variation in color between individuals is likely related to the last algae it ate.
    Members of the family have the back covered in leaf-like cerata, which in Polybranchia contain fine branching digestive gland ducts, but in Cyerce the digestive gland reaches only into the basal ceratal stalk. An other difference is that in Cyerce the sole of the foot has a transverse groove behind the head which is absent in Polybranchia.

References :

Bill Rudman Seaslug site : Sea Slug Forum : Polybranchia orientalis
   Nudipixel Polybranchia orientalis

Publications :

Jensen, K.R. (2007). Biogeography of the Sacoglossa (Mollusca, Opisthobranchia). Bonner Zoologische Beiträge. 55: 255–281.
    Kelaart, E.F. (1858). Description of new and little known species of Ceylon nudibranchiate molluscs and zoophytes. Journal of the Ceylon Branch of the Royal Asiatic Society, Columbo, 3(1) : 84-139.
    Marshall, J.G. & Willan, R.C. (1999). Nudibranchs of Heron Island, Great Barrier Reef - A Survey of the Opisthobranchia (Sea Slugs) of Heron and Wistari Reefs. Backhuys Publishers Leiden.

Other photos of Polybranchia orientalis complexe :

Philibert Bidgrain Mayotte, Mbouanatsa, less 1 m, 2 Jully 2016, size : 40 mm During the night   Bifurcated rhinophores detail (a)

Philibert Bidgrain Reunion, "Kelonia center", at Saint Leu, 2 July 2010, size : 50 mm   Probably spawn of this species...

	The back covered in leaf-like cerata contain fine branching digestive gland ducts.
In Polybranchia, the sole of the foot hasn't a transverse groove behind the head

Alain Barrère Reunion, 10 October 2004 P.orientalis is a sacoglossa and therefore feeds on algae. The variation in color between individuals is likely related to the last algae it ate.

Philibert Bidgrain Reunion, Etang salé lagoon, less 1 m, 1 February 2007, size : 20 mm P.orientalis is a sacoglossa and therefore feeds on algae. The variation in color between individuals is likely related to the last algae it ate. The rhinophores are long, forked (bifurcated) (a)

Mayotte, a green Polybranchia orientalis, at Sada, by Philibert Bidgrain