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Pinna bicolor (Family Pinnidae)

Razor Shell

Distribution:

The Razor Shell is a widespread species found around most Australian shores, especially in southern Australian waters with the possible exception of Tasmania and south-western Western Australia. It is widespread in the Indian Ocean as well as the western Pacific. (WA, NT, QLD, NSW, VIC, SA)

Features:

The Razor Shell is a common, distinctive, very widespread and variable species. It is a very large, broad and thin, triangular shaped bivalve. Its shape could be described as wedge- or fan-shaped. Its length may be 400-500mm and width 150 mm. It is called Razor Shell because of its long, thin, sharp upper edge, which may be so thin that it may be brittle. The equivalve shell halves are sculptured with 8 to 17 irregular ribs, along with concentric folds and striations. The dorsal margin is straight to concave or broadly sinuous. The posterior adductor scar is large while the anterior is small or absent. The ligament holding the halves together is moderately thick. There are no hinge teeth. A thread-like byssus is present anchoring the shell into the mud. The partially translucent Razor Shell is purplish-brown to colour, with a distinctive iridescent nacreous sheen.

Ecology/Way of Life:

Although not a rocky shore inhabitant, it may be found in the mud at the seaward face of many rocky or stony shores. It is gregarious, often found in the company of others in shallow sand and seagrass beds. It sits vertically with its sharp end embedded some distance into the soft muddy bottom in areas of low to moderate water movement.

Interaction with Humans/Threats:

Razor Shells are eaten as food in the Indo-West Pacific regions. Presently they do not appear to be harvested in Australian waters, although they were once sold in South Australia. Compared to the size of the shell the volume of meat is minimal. Overseas the long, silky byssus strands of some species of Pinna were woven with silk into gloves and other articles.

Other Comments:

Other common names are Fan Mussels and Razor Clam.

Further Reading:

Bennett, I. (1987). W.J. Dakin's classic study: Australian Seashores. p.320, Angus and Robertson.

Davey, K. (1998). A Photographic Guide to Seashore Life of Australia. p.124, New Holland Press.

Edgar, G.J. (1997). Australian Marine Life: the plants and animals of temperate waters. p.289, Reed.

Macpherson, J.H. and Gabriel, C.J. (1962). Marine Molluscs of Victoria. p.298, Melbourne Univ. Press. Described as Atrina tasmanica

Shepherd, S.A. and Thomas, I.M. (1989). Marine Invertebrates of Southern Australia. pt. II. p.637, South Aust. Govt. Press.

Wells, F.E., and Bryce, C.W. (1988), Seashells of Western Australia. p.154, Western Australian Museum.

Gastropods. A.H. and A.W. Reed.

Acknowledgments:

Text, map and photograph by Keith Davey.

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