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This species has been observed on Mayotte, Seychelles, Madagascar, Zanzibar

Order : Sacoglossa Superfamily : Limapontioidea Family : Caliphyllidae Distribution : Indo-West Pacific Maximal size : 30-40 mm Abundance : (May) Seldom if ever on the fore reef zone Species characteristics : The cerata are basically black and gold. The margin of each cerata is vivid white and below that is usually a golden band. Below that again are many golden spots The long bifurcated rhinophores are black with pale longitudinal lines extending up both forks
	Showing species characteristics...	Photo Yvon Gildas Mayotte, Passe en S, buoy n°6, 6 m, 24 June 2009

See more about : Sightening and mating periods

Remarks :

Identification confirmed by Nathalie Yonow and Hsini Lin

Bibliographic data :

The same colouration is usually present on both faces of each cerata
    The body is a typical shape for a species of Cyerce with bifurcating rhinophores
    The sole of the foot bears a groove across its center
    It lays a flat, broad, white egg masses consisting of three and a quarter turns.
    This Sacoglossa can change the orientation of its cerata according to its behavior.
               - At rest, the cerata are flattened and overlapped in longitudinal series like scales
               - When this Sacoglossa crawls, the cerata are elevated and curled
               - When strongly stimulated, this Sacoglossa swims by powerfully flapping its cerata in coordinated waves
    The cerata are cast off (autotomised) very readily when an animal is irritated, even touched lightly
    In the West Pacific they feed on the green algae Chlorodesmis fastigiata, commonly known as turtle weed.
    C. nigricans is closest to C. nigra but that species has a series of transverse white line across the outer surface of the cerata instead of the golden spots

References :

Bill Rudman Seaslug site : Sea Slug Forum : Cyerce nigricans
   Nudipixel Cyerce nigricans

Publications :

Pease, W.H. (1866). Remarks on nudibranchiata inhabiting the Pacific islands, with descriptions of two new genera. American Journal of Conchology 2(2) : 204-208
    Jensen, K.R. (2007). Biogeography of the Sacoglossa (Mollusca, Opisthobranchia). Bonner Zoologische Beiträge. 55: 255–281

Other photos of Cyerce nigricans :

Yvon Gildas Mayotte, Passe en S, buoy n°6, 6 m, 25 July 2009 The margin of each cerata is vivid white (a) and below that is a golden band (b). Below that again are many golden spots (c)

Nicole Gravier Bonnet Bassas de India, In the green algae Chlorodesmis sp, (probably fastigiata) commonly known as turtle weed.

Christophe Mason-Parker Seychelles, Curieuse Island, 2 m, 23 September 2010 The margin of each cerata is vivid white and below that is a golden band. Below that again are many golden spots.

Jacques Vieria Madagascar, Nosy Bé, 16 m, July 2017, size : 30 mm

Zanzibar, Cyerce nigricans by Arnaud Douay