This species has been observed on Mauritius Island

Order : Pleurobranchomorpha Superfamily : Pleurobranchoidea Family : Pleurobranchidae Distribution : Indo-West Pacific Maximal size : 200 mm Abundance : Species characteristics : The mantle is translucent clear with a reticulate pattern of brown encircling the white-tipped "mamillae" (breast-like tubercles) which cover the mantle. The oral veil has about 16 ventrally projecting sensory branched papillae There is a caudal spur on the top of the tail.
	Showing species characteristics...	Photo Yann von Arnim Mauritius, "Mahebourg Marine Farm", 22 m, 30 September 2010, size : 100 mm

See more about : Sightening and mating periods

Remarks :

Identification confirmed by Nathalie Yonow
    Synonymous : (according Worms)           
               - Pleurobranchaea gemini Macnae, 1962

Bibliographic data :

  The foot is a dark brown with opaque white patches
    Species of Pleurobranchaea are carnivorous hunters, probably eating a wide variety of prey items. Little is known of the diet of individual species although
            - Marcus & Gosliner (1984) report finding a 65 mm long specimen of P. brockii with 4 specimens (longest 18mm) of Philine aperta in its stomach.
            - When crawling on the sand, it can also eats some small tube-dwelling sea anemones
            - According Kathe Jensen : P. brockii is a very common subtidal species in Hong Kong, where it grows to a considerable size (>20 cm). The larger specimens are often cannibalistic, whereas smaller individuals have been found with cephalaspids ( Philinopsis cf. cyanea, Philine orientalis, Ringicula cf. doliaris ) in the crop. I once found a specimen, which had eaten a smaller specimen of P. brockii, which again had Philinopsis cf. cyanea in its crop, and the Philinopsis had some Ringicula shells in its intestine. How is that for a "food chain"?
    Like Euselonops luniceps, it 's a sand-dwelling pleurobranch

References :

Bill Rudman Seaslug site : Sea Slug Forum : Pleurobranchaea brockii
   Nudipixel Pleurobranchaea brockii

Publications :

Bergh, L.S.R. (1897). Malacologische Untersuchungen. In : C.G. Semper, Reisen im Archipel der Philippinen, Wissenschaftliche Resultate. Band 7, Heft 1-2(Die Pleurobranchiden) : 1-115, Pls. 1-8.
    Jensen, K.R. (1997) Cannibalism in an opisthobranch mollusc, Pleurobranchaea brockii Bergh, 1897 from Hong Kong waters. Phuket Marine Biological Center Special Publication, 17(1) : 41-46
    Marcus, E. & Gosliner, T.M. (1984) Review of the family Pleurobranchaeidae (Mollusca, Opisthobranchia). Annals of the South African Museum, 93(1) : 1-52

Other photos of Pleurobranchaea brockii :

Yann von Arnim Mauritius, "Mahebourg Marine Farm", 22m, 30 September 2010, size : 100 mm   A lot of group of several specimens were observed on the same day....

Yann von Arnim Mauritius, "Mahebourg Marine Farm", 22m, 5 October 2010, size : 100 mm A dead specimen The oral veil has about 16 ventrally projecting sensory branched papillae (a) There is a caudal spur (b) on the top of the tail.

 More photos from Indian Ocean

Mauritius, Pleurobranchaea brockii at Pointe d'Esny, by Geoffrey Summers