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Phylum Mollusca > Class Gastropoda
Giant top shell snail
Tectus niloticus
Family Tegulidae
updated Sep 2020
Where seen? This enormous conical snail is sometimes seen among large boulders and artificial seawalls on Southern shores. 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, a sharp-pointed cone, with spirals of bumpy ridges. Upperside orangey with slanted brown bars, but often hidden by encrusting lifeforms. Underside white with a pretty spiral pattern of dark red spots. Shell base outer edge on young snails is scalloped, smooth in older snails. 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 mottled, foot large, mantle edge sparsely fringed with long tentacles. Head brown with three white circles and long tentacles.

Pulau Jong, Apr 11

Sentosa, Nov 11

Operculum thin with concentric rings.


Head brown with three white circles. Sparse tentacles on mantle edge.
Sentosa, Nov 11

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

Giant top shell snails on Singapore shores
On wildsingapore flickr

Other sightings on Singapore shores


Berlayar Creek, Oct 17
Photo shared by Abel Yeo on facebook.

Labrador, Nov 18
Photo shared by Loh Kok Sheng on facebook.


Young snail. Shell base has scalloped edge.
St John's Island, Jan 20
Photo shared by Marcus Ng on facebook.

Young snail. Shell base has scalloped edge.
St John's Island, Jan 20
Photo shared by Marcus Ng on facebook.


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

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

Beting Bemban Besar, Nov 18
Photo shared by Liz Lim on facebook..


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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