Colour variation in the shell of Pupa strigosa

June 3, 2009
From: Bill Rudman

To acompany the message from Gary Cobb and Dave Mullins [#22463], here are some examples of the colour variability in  Pupa strigosa.

Pupa  strigosa is one of the most common of the tropical members of the genus. It is white with black spots as in P. solidula, but the shell is more slender, and the black spots are usually separated into three wide bands on the body whorl by three white spiral lines. However in some animals the black spots are not separated into bands, and in others, the spots merge to form blackish longitudinal bands down the shell. All variations can be found in single populations and the differences are not related to locality. To show this I have included examples of animals from the far north of tropical Queensland to the temperate waters of Sydney Harbour.

The orange-brown colouration on some shells is a thin organic, non-calcareous layer called the periostracum. It is present in many acteonids but is often transparent. In others it is worn off and only remains in the spiral grooves.

Widespread throughout the Indo-West Pacific. Solidula affinis A. Adams 1855 is probably a synonym of strigosa. But seems there are earlier usages of  Pupa affinis (Rossmaessler, 1839; Aradas & Maggiore, 1843). In southeastern Australia it has commonly been identified as Pupa fumata (Reeve, 1865).

A. B. Dingo Beach, Cape Gloucester, Queensland, Australia. pre 1952. AM C75572. Shell length: A - 11.9 mm; B - 14.5 mm. C. D. E. Lady Musgrave Is, Bunker Group, Great Barrier Reef, QLD, Australia. Lagoon, pre 1961. AM C435193. Shell length: C - 16.7 mm; D - 13.6 mm; E - 14.0 mm. F.G. off The Spit, Middle Harbour, Sydney, NSW, Australia. pre 1980. AM C435217. Shell length: F - 15.15 mm, G - 14.1 mm. Photos: D.L.Beechey.

Best wishes
Bill Rudman

Rudman, W.B., 2009 (Jun 3) Colour variation in the shell of Pupa strigosa. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from


Pupa strigosa

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