learn only 3 things about them ...
They are fierce predators! Some can bore a hole through
the prey's shell.
It takes them a long time to get at their prey. Don't
lay large collections of egg capsules on the rocks.
Where seen? You will almost be certain to meet this ferocious
predator on our rocky shores! Drills are commonly seen on boulders
and rocks, including man-made structures such as breakwaters and jetty
Features: Among the common drill
species on our shores are Rock-shell (Thais sp.), Drupes (Morula
sp.) and Murex (Chicoreus sp.). Drills usually have thick shells
and a thick operculum made of a horn-like material. Those with complicated
spines on their shells usually move by holding their shells above
the surface as they move along the surface.
Bored to Death: Drills that live
on the rocks are predatory molluscs that bore into other shelled creatures,
To bore a hole through the victim's shell, a drilling snail softens
the shell with a weak acid secreted by a special gland on the underside
of its foot. The softened shell is then slowly scraped off by the
snail's radula. The radula is the main physical tool in creating the
hole. It can take eight hours for a drill to get through a shell 2mm
Other drill food and feeding methods:
Some drills may also pry open the shells of bivalves
with a tooth on the lip of their shell. Others may also get to limpets
by inserting their proboscis under the limpet's shell.
Some may also hunt buried clams. Some prey on worms, the eggs of other
snails and even corals. Some deeper-water members of the Family Muricidae
eat worms and sea urchins.
We have also seen in groups of drills on silty sandy shores feeding
on nest mussels
To dye for: Many drills have a
gland that secretes a colourless mucus that turns purplish when exposed
to air. This secretion is a neurotoxin that paralyses or kills other
sea creatures. Humans have used this mucus as a rare dye (see below).
Drill Babies: Some drills lay
masses of bright yellow egg capsules. Each egg capsule may contain
20-40 eggs. The egg capsules turn purple when the free-swimming larvae
hatch. These swim about for a few weeks before they change into crawling
juveniles. In some, however, crawling juveniles emerge from the egg
Human uses: Since 1,500 BC in
the Mediterranean, snails of the Family Muricidae were harvested to
produce a dye called Tyrian purple (which was actually more maroon).
The dye resisted fading, but involved so much labour to produce that
only royalty and the very rich could afford it. Thousands of shells
were crushed to obtain minute quantities of the dye. The dye was worth
several times its weight in gold.
The dye industry brought fame and fortune to Tyre (now modern Lebanon).
Tyre was a great Phoenician city. In fact Phoenicia means "purple
people". Tyre ruled the seas and founded prosperous colonies
such as Cadiz and Carthage. The prosperity of Tyre allowed the arts
and sciences to flourish. For example, Marinus of Tyre was considered
the founder of mathematical geography and introduced the concept of
latitude and longitude in map design. As merchants who needed to keep
records, the Phoenicians simplified the 550 characters in the cuneiform
alphabet with a phonetic alphabet, based on distinct sounds, consisting
of 22 alphabets. This alphabet, with modifications introduced by the
Greeks and Romans, is the one we use today.
predators, some drills are considered a pest on oyster farms in Taiwan
drills have become useful as bioindicators of pollutants in the environment,
such as for anti-fouling chemicals used to prevent encrusting animals
from growing on ships and other installations in the sea. The
toxins kill drill larvae, or result in deformities in adults.
Status and threats: Chicoreus
ramosus is listed as 'Endangered' and the Murex
snail (Murex trapa) as 'Vulnerable' in the Red List of
threatened animals of Singapore. Our other drills are not on this
list. However, like other creatures of the intertidal zone, they are
affected by human activities such as reclamation and pollution. Trampling
by careless visitors and over-collection can also have an impact on
Drills laying eggs on a rock
Pulau Sekudu, Jan 06
Close up of egg capsules
Changi, Jul 05
A 'gang' of drills stuck onto a clam.
Tuas, May 07
A drill with what seems to be a
small bivalve in its shell opening.
Pulau Hantu, Feb 08
Kusu Island, Dec 04
Different kinds of Drill egg capsules.
Punggol, Jun 12
Chek Jawa, Apr 08
Muricidae recorded for Singapore
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.
commonly seen awaiting identification
Species are difficult to positively identify without
On this website, they are grouped by external features for convenience
Chicoreus brunneus (Burnt murex)
Chicoreus capucinus (Mangrove
(Ramose murex) (EN: Endangered)
Chicoreus torrefactus (Firebrand murex)
(Rare-spined murex snail) (VU: Vulnerable)
Semiricinula fusca (Dark drill)
(Thais gradata) and Ketem (Chicoreus capucinus)
Ng, Peter K. L. & N. Sivasothi, 1999. A
Guide to the Mangroves of Singapore II (Animal Diversity).
Singapore Science Centre. 168 pp.
Murex (Murex martineaus), Mangrove Murex (Chicoreus
capucinus), Thais and Morula Tan, Leo W. H. & Ng, Peter
K. L., 1988. A
Guide to Seashore Life. The Singapore Science Centre,
Singapore. 160 pp.
murex (Chicoreus ramosus) and Rare-spined
murex (Murex trapa) on the NParks Flora and Fauna website.
Muricidae on The Gladys Archerd Shell Collection at Washington
State University Tri-Cities Natural History Museum website: brief
fact sheet on drills with photos
Muricidae (Murex, Rock or Coral shells) on the The
Seashells of New South Wales website by Des Beechey Research
Associate, Australian Museum: family introductions with photos
of shells and detailed fact sheets for many species.
shells (Family Muricidae) on Life
on Australian Seashores by Keith Davey on the Marine Education
Society of Australia website: Fact sheet on drills and details
on various species found in Australia.
Muricidae 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.
of molluscs for personal adornment on the Man and Molluscs
website: an introduction to the wide range of dyes produced by
members of the Family Muricidae with links to photos of the shells.
purple: details about the chemical structure of the dye and
how it was collected in the past and a massive bibliography of
further readings on the subject.
- 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.
- Wee Y.C.
and Peter K. L. Ng. 1994. A First Look at Biodiversity in Singapore.
National Council on the Environment. 163pp.
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.
- Abbott, R.
Tucker, 1991. Seashells
of South East Asia.
Graham Brash, Singapore. 145 pp.