snails usually hunt and rest under the sand. Look for
trails in the sand!
are fierce predators that hunt other snails and clams.
The body of a moon snail can inflate to many times the
size of its shell.
These fierce burrowing snails are commonly seen on our sandy shores.
These snails are more commonly seen above ground at night. But a keen
observer may still detect their presence by the distinctive trails
these snails leave on the surface as they quietly burrow just beneath
What are moon snails? Moon snails
belong to the Family Naticidae. These include the Genus Natica,
which have a thicker operculum that is shell-like (usually white);
and the Genus Polinices, which have a thin operculum made of
a horn-like material (usually yellowish) with several whorls. The
Naked moon snails of the Genus Sinum have thin shells and very
Features: About 2cm. When a moon
snail is fully extended out of its shell, it has an amazingly large
body compared to its shell. It achieves this by inflating its tissues
The body forms a wedge shape that helps the snail move under the sand.
The front of the foot is used like a plough. A part of the foot covers
the head as a protective shield. The tentacles and siphon stick out
of this shield. The mantle (a part of its body) extends in two flaps
over the shell on either side.
A moon snail's shell often remains shiny and lustrous because the
mantle envelopes its shell, and the snail spends most of its time
under the sand. Encrusting animals have little chance of establishing
on the shell of a living Moon snail.
What do they eat? Moon snails
are fierce predators. They feed on bivalves and snails. A moon snail
wraps its huge foot around the hapless prey to suffocate it. If this
fails, it has a gland at the tip of its proboscis that secretes an
acid to soften the victim's shell. With its radula, a hole is slowly
drilled through the shell. The hole created by a moon snail is usually
neat and bevelled.
Moon babies: The sand collar is
the moon snail's egg mass. A moon snail lays her eggs at night. The
eggs are laid singly in capsules which are embedded in a matrix of
sand grains - a combination of mucus and sand which forms a gelatinous
sheet that hardens. She lies at the center of the collar as she creates
it, so the hole in centre of the collar gives an indication of the
size of the mother snail. Although the collar feels hard, plasticky
and appears dead, each collar can contain thousands of living eggs.
When the eggs hatch, the collar disintegrates. Thus, an intact collar
has living snails in it! Please don't damage the sand collars. Sand
collars are sometimes numerous on the sand bar and seagrass lagoon.
More photos of sand collars we have seen.
Role in the habitat: When a moon
snail dies, its shell is quickly taken over by a hermit crab. Many
of the moon snail shells you see on the surface will probably be so
occupied. Living moon snails are rarely seen above ground during the
Human uses: Some larger moon snail
species are sold as food in Asian markets.
Status and threats: Like other
creatures of the intertidal zone, the rest of they are affected by
human activities such as reclamation and pollution. Trampling by careless
visitors and over-collection can also have an impact on local populations.
The body can expand
to be MUCH bigger than the shell Changi, Jun 06
Tiny button snails leaping away
from a hunting moon snail. East Coast, Jun 06
Clam shell with hole neatly drilled,
possibly by a moon snail? Changi, Oct 10
Sand collar: egg mass of a moon snail. more photos of sand collars Pulau Sekudu, Jul 03
Changi, Jul 11
Bivalve escaping a moon snail!
Using its long foot, the bivalve 'leaps' away to safety.
Moon snail attempting
to eat a bivalve as big as itself!
Filmed on Cyrene Reef Aug 2013
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.