The turbinids are sometimes called turban snails for the turban-like shells of many species. Most turban snails have thick and hard calcareous opercula which are flat on the inside, but convex on the outside. But there are exceptions. These pretty opercula come in different colours and patterns, and are sometimes called "cat's eye". They are used in shell jewelleries and bigger ones are used as paper weights. Turban snails feed on algae. Some species may come with spines. Most of these snails are collected for food.
I have only seen four species of turban snails on our shores so far (thanks to Siong Kiat who gave tips on how to identify them!). You may want to take a look at my diagram on the parts of a snail's shell if you are not familiar with the names of the parts, so as to better understand the terms used below.
The Brown Turban Snail (Turbo bruneus) is one of the two commonly seen intertidal turban snail species found on Singapore's rocky shores or reef flats. It can be differentiated from the other species by its operculum, which is rough and covered with tiny bumps. The outward-facing side of the operculum is dominated by a big dark green patch. The spiral cords are marked with tiny scales, as seen in the above photo, and hence the shell feels rough when you run your finger along the whorls.
"Bruneus" means brown in Latin, and hence this animal got its name from the light brown base colour of the shell. Running down the length of the shell are very dark brown to black wavy bands.
The Ribbed Turban Snail (Turbo intercostalis) is the other commonly seen turban snail species on the rocky shores or reef flats of Singapore. "Intercostal" means "between the ribs". It can be differentiated from the previous species by the generally smooth and shiny operculum, though the sides may have little bumps or depressions. The colour is usually pale green (or brown) and white.
The shell is usually slightly greener, with lots of brown patches. If you run your finger along the spiral cords, it will feel smoother, since it lacks the numerous scales which mark the surface of the previous species.
It can be a challenge to differentiate the two species based on the shell though, as they are often covered with encrusting organisms or badly eroded. And hence, it is usually still easier to differentiate them in the field by looking at the operculum. The above is a Ribbed Turban - despite the small depressions and bumps by the sides, the operculum is still generally smooth and lacks the dark green patch.
The Spurred Turban Snail (Astralium calcar) is an uncommon turban snail in our local waters, and is usually found on coral reefs and reef flats. The shell is marked by a spiral row of blunt spines along the whorls, and is usually covered with encrusting organisms, such as red coralline algae in the above photo.
The underside is marked by tiny bumps. The operculum is greenish, while the aperture has light yellow-green stains.
The Giant Turban Snail (Tectus niloticus) is quite unmistakable on our rocky shores, with its huge size, sometimes to more than 12cm tall! It is top-shaped, with dark wavy bands running down the shell. The shell is often covered with algae in the field. It was previously classified as a top shell (family Trochidae), but recent genetic studies showed that it should be a turban snail instead.
Juvenile Giant Turban Snails, due to their small sizes, are especially easily mistaken for top shells. They can be differentiated by the spiral rows of nodules on the shell though.
The underside is often marked with wavy bands, though in some cases they may be very well-eroded. This is a commercially very important species, as it is often collected for food.
Snail families that resemble turban snails:
Turban snails are easily confused with the closely related top shells, especially for top shells that are turban-shaped. The Toothed Top Shell (Monodonta labio) above is one of the top shells that look like turban snails. Find out more about the top shells at my page on Top Shells (Phylum Mollusca: Family Trochidae) of Singapore.
Chilodontid snails from the family Chilodontidae can also be confused with the turban snails, as they are also turban-shaped. The chilodontid snails, however, come with a corneous operculum, such as the Four-keeled Euchelus (Euchelus quadricarinatus) above. Find out more about the chilodontid snails at my page on Chilodontid Snails (Phylum Mollusca: Family Chilodontidae) of Singapore.
References
I have only seen four species of turban snails on our shores so far (thanks to Siong Kiat who gave tips on how to identify them!). You may want to take a look at my diagram on the parts of a snail's shell if you are not familiar with the names of the parts, so as to better understand the terms used below.
The Brown Turban Snail (Turbo bruneus) is one of the two commonly seen intertidal turban snail species found on Singapore's rocky shores or reef flats. It can be differentiated from the other species by its operculum, which is rough and covered with tiny bumps. The outward-facing side of the operculum is dominated by a big dark green patch. The spiral cords are marked with tiny scales, as seen in the above photo, and hence the shell feels rough when you run your finger along the whorls.
"Bruneus" means brown in Latin, and hence this animal got its name from the light brown base colour of the shell. Running down the length of the shell are very dark brown to black wavy bands.
The Ribbed Turban Snail (Turbo intercostalis) is the other commonly seen turban snail species on the rocky shores or reef flats of Singapore. "Intercostal" means "between the ribs". It can be differentiated from the previous species by the generally smooth and shiny operculum, though the sides may have little bumps or depressions. The colour is usually pale green (or brown) and white.
The shell is usually slightly greener, with lots of brown patches. If you run your finger along the spiral cords, it will feel smoother, since it lacks the numerous scales which mark the surface of the previous species.
It can be a challenge to differentiate the two species based on the shell though, as they are often covered with encrusting organisms or badly eroded. And hence, it is usually still easier to differentiate them in the field by looking at the operculum. The above is a Ribbed Turban - despite the small depressions and bumps by the sides, the operculum is still generally smooth and lacks the dark green patch.
The Spurred Turban Snail (Astralium calcar) is an uncommon turban snail in our local waters, and is usually found on coral reefs and reef flats. The shell is marked by a spiral row of blunt spines along the whorls, and is usually covered with encrusting organisms, such as red coralline algae in the above photo.
The underside is marked by tiny bumps. The operculum is greenish, while the aperture has light yellow-green stains.
The Giant Turban Snail (Tectus niloticus) is quite unmistakable on our rocky shores, with its huge size, sometimes to more than 12cm tall! It is top-shaped, with dark wavy bands running down the shell. The shell is often covered with algae in the field. It was previously classified as a top shell (family Trochidae), but recent genetic studies showed that it should be a turban snail instead.
Juvenile Giant Turban Snails, due to their small sizes, are especially easily mistaken for top shells. They can be differentiated by the spiral rows of nodules on the shell though.
The underside is often marked with wavy bands, though in some cases they may be very well-eroded. This is a commercially very important species, as it is often collected for food.
Snail families that resemble turban snails:
Turban snails are easily confused with the closely related top shells, especially for top shells that are turban-shaped. The Toothed Top Shell (Monodonta labio) above is one of the top shells that look like turban snails. Find out more about the top shells at my page on Top Shells (Phylum Mollusca: Family Trochidae) of Singapore.
Chilodontid snails from the family Chilodontidae can also be confused with the turban snails, as they are also turban-shaped. The chilodontid snails, however, come with a corneous operculum, such as the Four-keeled Euchelus (Euchelus quadricarinatus) above. Find out more about the chilodontid snails at my page on Chilodontid Snails (Phylum Mollusca: Family Chilodontidae) of Singapore.
References
- Oliver, A. P. H. 2012. Philip's guide to seashells of the world. Philip's, London. 320 pp.
- Tan, K. S. & L. M. Chou, 2000. A guide to common seashells of Singapore. Singapore Science Centre, Singapore. 168 pp.
- Tan, S. K. & H. P. M. Woo, 2010. A preliminary checklist of the molluscs of Singapore. Raffles Museum of Biodiversity Research, National University of Singapore, Singapore. 78 pp. Uploaded 02 June 2010.
- Tan, S. K. & R. K. H. Yeo, 2010. The intertidal molluscs of Pulau Semakau: preliminary results of “Project Semakau”. Nature in Singapore, 3: 287–296.
- World Register of Marine Species. 2012. Retrieved Oct 3, 2012, from http://www.marinespecies.org.
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