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Tectus pyramis (Family Trochidae)

Pyramid Trochus

Distribution

Distribution:

This species has an Indo-West Pacific distribution. In Australia, this species has a tropical distribution, ranging from Rottnest Island, WA, across the NT and around Qld shores to Hervey Bay, Qld (WA, NT, QLD).

Features:

This high-spired gastropod is easy to identify by its perfect cone-like shape, colour and its angled striated pattern. It grows to 60-80 mm high and wide. The Pyramid Trochus has a solid, conical-shaped shell with flat sides and a sharply angled margin to the flat base. The height and width of the shell are almost equal. The smooth sculpture has some growth lines that are crossed by oblique axial striations and weak nodules near the breaks, called sutures. The umbilicus is sealed, while the columella is smooth and curved. The umbilicus is a depression at the axial base of a spiral shell. The columella is the central axis of a spiral univalve mollusc. The outer lip of the aperture has several distinct bumps called denticles on the inner margin near the base. The operculum is circular and is composed of horn-like material. When weathered, its peak may be eroded.

The exterior colour is grey, cream or pink and the base white, green or light blue. The shell is nacreous beneath the brown coloured periostracum cover.

Ecology/Way of Life:

The Pyramid Trochus occurs in large numbers on coral reefs and on rocky shores. It is an algae and detritus feeder. Sexes are separate and as the male does not have a penis, its gametes are shed into the water where fertilisation occurs.

Preferred Image

Interaction with Humans/Threats:

It is unknown if human activity poses a threat to this species. The shells from other larger trochids from northern Australian waters were once used to make buttons and jewellery.

Other Comments:

Tectus pyramis , (Born, 1778). Trochus obeliscus, Gmelin, 1791, and Tectus acutus, Lamarck, 1822, are synonyms. Tectus comes from the Latin word tectum meaning a roof, and pyramis is the Greek word for a solid figure on a triangular, square or polygonal base with triangular sides meeting at a point.

Further Reading:

Davey, K. (1998) A Photographic Guide to Seashore Life of Australia p.95. New Holland Press, Sydney.

Short, J.W. & Potter, D.G. (1987). Shells of Queensland and the Great Barrier Reef: Marine Gastropods. p.10, Golden Press, Drummoyne.

Wells, F.E. & Bryce, C.W. (1988) Seashells of Western Australia. p.40, Western Australian Museum.

Wilson, B.R. & Gillett, K. (1979) A Field Guide to Australian Shells: Prosobranch Gastropods. p. 38, Reed.

Acknowledgments:

Text, map & photograph by Keith Davey.

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Images and Multi-media:  
Attached Image  
image/jpeg 120636 bytes Pyramid Trochus
Distribution Map  
image/gif 1018 bytes Distribution of Pyramid Trochus

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