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Phylum Mollusca > Class Gastropoda
Drills
Family Muricidae
updated Sep 12
if you 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 remove drills.
Some 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 pilings.

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, especially barnacles.

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 thick. Yawn!

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 (Muscilista sp.)

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 capsules.

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.

Voracious predators, some drills are considered a pest on oyster farms in Taiwan and Japan.

Recently, 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 local populations.

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





Family Muricidae 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

  Drills commonly seen awaiting identification
Species are difficult to positively identify without close examination.
On this website, they are grouped by external features for convenience of display.
  Chunky drills
Elegant drills
Knobbly drills
Reef murex snails

  Family Muricidae
  Aspella anceps

Chicoreus axicornis
Chicoreus banksii
Chicoreus brunneus
(Burnt murex)
Chicoreus capucinus
(Mangrove murex)
Chicoreus ramosus
(Ramose murex) (EN: Endangered)
Chicoreus torrefactus
(Firebrand murex)

Coralliophila rubrococcinea

Cronia margariticola=^Drupella margariticola

Drupella concatenata

Ergalatax contracta

Favartia cirrosa
Favartia peasei
Favartia sykesi

Lataxiena blosvillei
Lataxiena fimbriata

Mancinella echinata
Mancinella echinulata

Mipus gyratus

Morula andrewsi
Morula spinosa
Morula musiva=^Tenguella musiva
Morula subnodulosa

Muricodrupa fiscella
Muricodrupa stellaris

Murex ternispina
Murex trapa
(Rare-spined murex snail) (VU: Vulnerable)
Murex troscheli

Orania ficula

Phyllocoma
sp.

Phyllonotus lacinatus

Pterynotus alatus

Purpura bufo

Rapana rapiformis

Semiricinula fusca
(Dark drill)
Semiricinula muricoides

Thais bitubercularis=^Reishia bitubercularis
Thais clavigera
Thais gradata=^Indothais gradata
Thais javanica=^Indothais javanica
Thais jubilaea=^Reishia jubilaea
Thais lacera=^Indothais lacera
Thais malayensis=^Indothais malayensis
Thais rufotincta=^Indothais rufotincta
Thais sacellum=^Indothais sacellum

Vitularia miliaris

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.
  • Wee Y.C. and Peter K. L. Ng. 1994. A First Look at Biodiversity in Singapore. National Council on the Environment. 163pp.
  • 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.
  • Abbott, R. Tucker, 1991. Seashells of South East Asia. Graham Brash, Singapore. 145 pp.
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