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Phylum Mollusca > Class Gastropoda
Giant top shell snail
Tectus niloticus
Family Tegulidae
updated Oct 2016
Where seen? This enormous snail is sometimes seen large boulders, sea walls and jettys on undisturbed Southern shores, usually near good reefs. Elsewhere, it is found in coral reefs, typically in shallow, high-energy barrier and fringing reefs. It was previously known as Trochus niloticus in Family Trochidae.

Features: Base diameter 8-15cm. The largest of our top shells, shell thick, heavy, shaped like a pointed cone, with spirals of bumpy ridges. The upperside orangey with slanted brown bars, but this is often hidden by encrusting lifeforms. Underside white with a pretty spiral pattern of dark red spots. Shell base outer edge is scalloped (not smooth). Operculum, thin, made of a horn-like material with concentric rings, yellow or brown. The flexible operculum allows the animal to withdraw deep into the coils of the shell. Body pale, large foot pale on the underside, mottled on the upperside. A pair of long tentacles at the head which is brown with three white circles. Larger specimens usually found in deeper water, but small ones often seen under stones on the intertidal.

What does it eat? It eats filamentous algae and generally avoids sandy bottoms and living corals.

Human uses: This large snail is the most economically important snail in the tropical West Pacific. Both as an important traditional food and a leading export item as the source of mother-of-pearl buttons and jewellery. Total annual harvest is estimated at 5-6 million tons. As a result of severe overfishing, in many places policies are in place to manage their harvest and aquaculture trials are underway.


Status and threats: The snail used to be abundant in Singapore in the 1960's but is now listed as 'Vulnerable' on the Red List of threatened animals of Singapore. Like other creatures of the intertidal zone, it is affected by human activities such as reclamation and pollution. Trampling by careless visitors and over-collection can also have an impact on local populations.

Pulau Jong, Apr 11


Sentosa, Nov 11

Operculum thin with concentric rings.

Sentosa, Nov 11

Kusu Island, Sep 09

Young snail. Shell base has scalloped edge.
Tanah Merah, Sep 13

Giant top shell snails on Singapore shores

Photos of Giant top shell snails for free download from wildsingapore flickr

Distribution in Singapore on this wildsingapore flickr map


Terumbu Selegie, Jun 11
Photo shared by James Koh on his blog.

Terumbu Buran, Nov 10
Photo shared by Loh Kok Sheng on his blog.
 


Terumbu Bukom, Nov 10
Photo shared by Loh Kok Sheng on his blog.

Terumbu Pempang Laut, Apr 11
Photo shared by Loh Kok Sheng on flickr.
 


Lazarus Island, Feb 11

Photo shared by Loh Kok Sheng on his flickr.

Pulau Senang, Jun 10

Photo shared by Loh Kok Sheng on his flickr.
 


Pulau Biola, Dec 09

Pulau Biola, Dec 09

Terumbu Berkas, Jan 10

Family Tegulidae recorded for Singapore
from Tan Siong Kiat and Henrietta P. M. Woo, 2010 Preliminary Checklist of The Molluscs of Singapore.
in red are those listed among the threatened animals of Singapore from Davison, G.W. H. and P. K. L. Ng and Ho Hua Chew, 2008. The Singapore Red Data Book: Threatened plants and animals of Singapore.
^from WORMS.

  ^Family Tegulidae
  ^Tectus niloticus=Trochus niloticus (Giant top shell snail) (VU: Vulnerable)
Tectus pyramis
^Tectus tentorium=Trochus tentorium

Links

References

  • Tan Siong Kiat and Henrietta P. M. Woo, 2010 Preliminary Checklist of The Molluscs of Singapore (pdf), Raffles Museum of Biodiversity Research, National University of Singapore.
  • Tan, K. S. & L. M. Chou, 2000. A Guide to the Common Seashells of Singapore. Singapore Science Centre. 160 pp.
  • Davison, G.W. H. and P. K. L. Ng and Ho Hua Chew, 2008. The Singapore Red Data Book: Threatened plants and animals of Singapore. Nature Society (Singapore). 285 pp.
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