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Austrocochlea odontis (Family Trochidae)

Checkered Top Shell

Distribution:

The Checkered Top Shell ranges from Waratah Bay, Victoria across to South Australia and around Tasmania (VIC, TAS, SA).

Features:

The Checkered Top Shell is solid, round, conical, and smooth. It grows to a height of 15 mm and a length of 15mm. Its five whorls are marked with very fine grooves. It has a less strongly sculptured surface than the eastern Australian Austrocochlea species. Its brown coloured operculum is horny, and round. It has a thin outer lip to the shell edge. The shell has a flattened base, sunken around the central region.

The Checkered Top Shell is dark grey to bluish black in colour, with numerous yellowish white markings in a fine checked pattern of dots or patches. The shell interior is green, with the edge of the aperture black. The edge of the columella is bright green. The aperture is round with a black edge. The interior of the shell is smooth and iridescent.

Another similar closely related Top Shell, with a southern Australian distribution is the Adelaide Top Shell, Austrocochlea adelaidei. Although both have a bright green edge to the aperture, the Adelaide Top Shell may be distinguished from the Checkered Top Shell by its brown or grey coloured shell with more coarse tessellated markings, stronger sculpture and eroded yellowish orange spire tip.

Ecology/Way of Life:

The Checkered Top Shell is found at and below mid-tide level on algae and algal mats as well as under stones in rock pools. It prefers sheltered and moderately exposed reef. It is a trochid (Family Trochidae) and is micro-algae grazer. There are both male and female trochids. They expel their sperm and gametes into the surrounding water where they combine to fertilise. The planktonic larvae may drift in the ocean currents for a week before settling.

The Checkered Top Shell is attractively coloured and easily recognised by its distinctive spotted pattern of light yellow to whitish spots and green interior.

Interaction with Humans/Threats:

Although considered common within its range, the Checkered Top Shell requires monitoring because of its very restricted distribution to the cooler shores of southern Australia.

Other Comments:

The word "odontis" refers to the single, feint tooth at the base of the columella. The animal is dark grey, speckled with yellow.

Further Reading:

Davey, K. (1988). A Photographic Guide to Seashore Life of Australia. p.89, New Holland Press.

Edgar, G.J. (1997). Australian Marine Life: the plants and animals of temperate waters. p.241, Reed.

Macpherson, J.H. & Gabriel, C.J. (1962). Marine Molluscs of Victoria. p.70, Melbourne Univ. Press.

Marine Research Group of Victoria. (1984). Coastal Invertebrates of Victoria: an atlas of selected species. p. 39, Museum of Victoria.

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

Acknowledgments:

Text, map & photograph by Keith Davey.

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