Order : Pleurobranchomorpha
Superfamily : Pleurobranchoidea
Family : Pleurobranchidae
Distribution : Tropical Indo-West Pacific
Maximal size : Usually 160 mm sometimes 300 mm
Abundance : Seldom on the rocky coast

Species characteristics :

The colour pattern ranges from very "dark form" to "plain yellow-brown form" with dark brown rings

One consistent element of the colouration is a serie of narrow, opaque white semicircles that outline clusters of pustules

Posteriorly, when it is crawling actively, the mantle was raised and folded to forme a very large and almost complete tubular siphon on the midline

Philippe Bourjon

Reunion, 25 February 2017

Identification confirmed by A. Valdés

Philibert Bidgrain

Mayotte, Mtsanga M'Titi Sada, less 1 m, 20 July 2010, size : 70 mm

Adults are most often dark plum red. One consistent element of the colouration is a serie of narrow, opaque white semicircles that outline clusters of pustules.

They have two well developed cylindrical rhinophores (a) on the head

The spawn (b) : a white ribbon...

Maurice jay

Reunion,

Juvenile has purple spots and a white reticulate pattern but hasn't a ring of small tubercles around each of the large ones like P. grandis.

See sp N 68 in "Nudibranchs of Heron Island" R. C. Willan for comparaison

Yann von Arnim

"Ferme marine" Mahebourg, Mauritius, January 2009, size : 120-150 mm

Adults are most often dark plum red. One consistent element of the colouration is a serie of narrow, opaque white semicircles that outline clusters of pustules.

Philibert Bidgrain

Reunion, Etang salé on the rocky coast, less 1 m, 7 November 2006, size : 12-15 mm

Crawling during the day on the substrate

This specimen looks like plain yellow-brown form of P. forskalii but this small specimen hasn't yet the serie of narrow, opaque white semicircles that outline clusters of pustules.

So it could be a small specimen of P. forskalii "plain yellow-brown form"

This specimen is very similar to Koretz's specimen in Opisthobranchs of Eilat
identified as P. mamillatus

Christophe Cadet

Réunion, Etang salé on the rocky coast, less 1 m, 14 December 2011, size : 25-30 mm

A specimen of the "plain yellow-brown form" with dark brown rings and the caracteristic serie of narrow, opaque white semicircles that outline clusters of pustules

Christophe Cadet

Réunion, Etang salé on the rocky coast, less 1 m, 2 January 2012, size : 40 and 50 mm

Two specimens of the "plain yellow-brown form", one yellow-brown and the second darker...

The darker specimen looks like the "dark form"

Yann von Arnim

"ferme marine" Mahebourg, Bambou dive site, Mauritius, 5 October 2010, size : 60 mm

A specimen of the plain yellow-brown form with dark brown rings and the caracteristic serie of narrow, opaque white semicircles (a) that outline clusters of pustules

When it is crawling actively , the posterior end of the mantle is raised into a temporary spout (b), characteristic of this species