Pleurobranchus peroni
Cuvier, 1804

Order: NOTASPIDEA
Superfamily: PLEUROBRANCHOIDEA
Family: Pleurobranchidae

PHOTO

UPPER: Adult, Koumac, New Caledonia, October 1993, 28mm long. (grows to at least 60mm).
MIDDLE: North Coast, New South Wales, Australia, March 1982, 20mm, showing intermediate colour form.
LOWER: Juvenile, Coffs Harbour Region, New South Wales, Australia, December 1990, showing typical juvenile colouration.
PHOTOS: Bill Rudman.

Very common widespread Indo-West Pacific species ranging in background colour from a pale translucent white, through yellow and brown to a deep purple. The mantle is covered in small tubercles each outlined by a polygon which is either deeper in colour than the background colour, or sometimes white. Juvenile specimens are usually distinctly different in colour with a translucent white background, some of the tubercles tipped with reddish purple and the mantle edged in orange or red. This colour form has been considered to be a distinct species (P. ovalis - Pease, 1868: Pruvot-Fol, 1954; Thompson, 1970; P. papillatus Risbec, 1951). As the animal grows, all the tubercules gradually colour, from the tip down, and the purple fades from the scattered purple-tipped tubercles. The various colour forms from juvenile to adult are similar to the juvenile forms of Pleurobranchus grandis but they can be distinguished by the absence of the white reticulate pattern in P. peroni. There are probably other names which have been given to this species, but the variable colour pattern, and ambiguous early descriptions, make identification difficult. Pleurobranchus zeylanicus Kelaart, 1859, Oscaniella nigropunctata Bergh are clearly this species as are two other species described from South Africa (Pleurobranchus inhacae Macnae,1962; Pleurobranchus xhosa Macnae, 1962) which are said to differ from P. peroni in the size of the prostate gland, much larger in P. peroni. Both appear to be juvenile specimens, which would explain the less developed prostate gland. Susania papillosa,is a another name given to a specimen from southern Africa, is most probably a purple colour form of this species. Pease (1868) reported this species from Tahiti (P. ovalis) and Risbec (1951) from New Caledonia (P. papillatus). It is unlikely that there is a name earlier than Cuvier's.

Reference:
• Cuvier, G.L. (1804). Mémoire sur la Phyllidie et sur le Pleurobranche, deux nouveaux genres de mollusques de l'ordre des gastéropodes, et voisins des patelles et des oscabrions, dont l'un est nu dont l'autre porte une coquille cachée. Annales du Muséum National d'Histoire Naturelle, Paris, 5: 266-276.

Authorship details
Rudman, W.B., 1999 (April 18) Pleurobranchus peroni Cuvier, 1804. [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/factsheet/pleupero

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