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Phylum Mollusca > Class Gastropoda
Tun shell snails
Family Tonnidae
updated Sep 2020
Where seen? This snail with a large, thin spherical shell is rarely seen. They are usually found in sandy bottoms in deeper water and thus living snails are rarely seen on the intertidal. Elsewhere, they are found in sandy areas especially in seagrass meadows.

Features: 9-10cm. The shell is thin but strong, nearly spherical with a short spiral and very large shell opening. Usually with spiralling ridges on the surface. Adult snails lack an operculum.

The Banded tun (Tonna sulcosa) is about 10cm with a rather thick shell that has flat spiral ribs. It is creamy white with 3-4 broad spiralling brown bands. It is found on fine sand and muddy bottoms.

The Spotted tun (Tonna dolium) is about 13cm and found on find sand and muddy bottoms.

Possibly the Spotted tun.
Changi, Jan 10

What do they eat? Mainly echinoderms such as sea cucumbers and crustaceans. The snail first paralyses the prey with a salivary secretion containing sulphuric acid before swallowing it whole! The animal has a large foot and can crawl and burrow rapidly.

Baby tuns: The egg mass is a wide gelatinous ribbon containing many small, transparent eggs. The planktonic larvae take a very long time to develop, thus some species are widely dispersed by ocean currents.

Human uses:
It is sometimes collected for food by coastal dwellers and the shell used as decorative items.

Tun shell snails on Singapore shores
On wildsingapore flickr

Other sightings on Singapore shores

Empty shell.
Chek Jawa, Jun 12
Photo shared by Loh Kok Sheng on flickr.

Empty shell.
Cyrene, Aug 13
Photo shared by Loh Kok Sheng on his blog.

Shell occupied by a hemit crab.
Cyrene, Aug 11

Family Tonnidae recorded for Singapore
from Tan Siong Kiat and Henrietta P. M. Woo, 2010 Preliminary Checklist of The Molluscs of Singapore.

  Family Tonnidae
  Tonna dolium (Spotted tun)
Tonna sulcosa
(Banded tun)

  • Family Tonnidae on The Gladys Archerd Shell Collection at Washington State University Tri-Cities Natural History Museum website: brief fact sheet with photos.
  • Family Tonnidae in the Gastropods section by J.M. Poutiers in the FAO Species Identification Guide for Fishery Purposes: The Living Marine Resources of the Western Central Pacific Volume 1: Seaweeds, corals, bivalves and gastropods on the Food and Agriculture Organization of the United Nations (FAO) website.


  • 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.
  • Abbott, R. Tucker, 1991. Seashells of South East Asia. Graham Brash, Singapore. 145 pp.
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