Version française...

This species has been observed on Reunion, Mayotte, Seychelles and Madagascar Islands

Order : Nudibranchia Suborder : Euctenidiacea Superfamily : Doridoidea Family : Discodorididae Distribution : South West Indian Ocean Maximal size : 30 mm Abundance : Species characteristics : The flattened ridges are yellow, yellow-brown to orange and the spaces in between are dark brown with bright white spots  without concentration of white spots forming a band around the mantle The rhinophores clubs are black (or dark purple-brown) and the stalks are translucent white with a dark streak up the posterior side The four to six sparsely branched gills have a dark purple-brown axis with white pinnules
	Showing species characteristics...	Photo Sandrine Flodrops Mayotte, Passe en S, 12 m, 4 March 2009, size : 25 mm

See more about : Sightening and mating periods

Remarks :

 Synonymous : (according Worms)
          - no synonymous

Bibliographic data :

There are two colour form.
               - The Western Pacific colour form. The white specks and spots are realtively small except in a wide band around the mantle edge where they are numerous corresponded to H. tessellata
               -The Indian Ocean colour form. The white spots are evenly spread over the brown parts of the mantle with no marginal concentration corresponded to H. indotessellata
    The dorsum is entirely covered with irregular ridges. At the junctions of two or more ridges, they are raised into a short, conical tubercle. In the mantle margin there is a number of small conical tubercles.
    There is a mid dorsal line down the posterior part of the foot extending beyong the mantle
    There is a thin opaque white or yellow orange line around the mantle edge.
    The rhinophoral and branchial sheaths are low and regular.
    The rhinophores are elongate, with 19 lamellae in a 24 mm preserved length specimen.
    The four to six sparsely branched gills, form a complete circle around the anus. In some specimen the axis is dark purple-brown with white pinnules, in other specimens the gills are white with scattered dark purple-brown patches.
    The oral tentacles are conical.
    The ventral colour is pale yellow with several large purple-brown spots in the mantle margin. There are numerous, longitudinal brown streaks or spots in the upper half of the sides of the foot.
    It probably feed on siliceous sponge

References :

Bill Rudman Seaslug site : Sea Slug Forum : Halgerda tessellata
   Nudipixel Halgerda tessellata

Publications :

Tibiriçá Y., Pola, M. & Cervera J.L. (2018). Systematics of the genus Halgerda Bergh, 1880 (Heterobranchia : Nudibranchia) of Mozambique with descriptions of six new species. Invertebrate Systematics. 32: 1388-1421

Other photos of Halgerda indotessellata :

Philibert Bidgrain Mayotte, N'Gouja, less 1 m, 8 April 2015, size : 10-12 mm

Sandrine Flodrops Mayotte, Passe en S, 12 m, 4 March 2009, size : 25 mm (a) There is a mid dorsal line down the posterior part of the foot extending beyong the mantle    (b) The rhinophores clubs are black (or dark purple-brown) and the stalks are translucent white with a dark streak up the posterior side    (c) The four to six sparsely branched gills have a dark purple-brown axis with white pinnules    (c) The branchial sheath is low and regular.

Marina Poddubetskaia Mayotte, Passe en S buoy n°8, 17 m, 4 November 2003, size : 16-18 mm The four to six sparsely branched gills have a dark purple-brown axis with white pinnules A specimen with large number of white dots in the dark area.

Matthias Deuss Mayotte, fringing reef of Mtsange M'Bouini, less 1 m, 21 December 2009, size : 30 mm There are supernumerary black dots (a) on one rhinophoral stlalk A specimen with large number of white dots in the dark area and with not interconnected orange ridge (b) .

Mayotte, Halgerda tessellata with large number of white dots on the dark area, by Sylvain Le Bris  

Reunion, Halgerda tessellata, at Les Avirons, by Sully Bachel  

Seychelles, Halgerda tessellata, at Mahé, by Christophe Mason-Parker

Mayotte, a pair of Halgerda tessellata, at N'gouja, by Philibert Bidgrain

Madagascar, Halgerda tessellata, at Nosy Bé, by Alain-Benoît Rassat