Squids and cuttlefish are fast moving shelless snails!
They have ten arms and two tentacles.
egg capsules are common on the shores. Don't step on them!
seen? These amazing animals are seasonally common on many
of our shores. Tiny squids are also common in seagrass areas, but
often overlooked. Their eggs are also seasonally seen. Although better
known as seafood, these delightful creatures are equally delicious
to observe, with their colour changes and busy behaviour. They are
more active at night.
What are squids and cuttlefish?
They are not fish! These animals are molluscs
(Phylum Molusca) like snails, slugs and clams; and cephalopods
(Class Cephalopoda) which include octopuses.
Most of the commonly encountered cuttlefishes belong to Order
Sepiida, while our commonly encountered squids belong to Order
Teuthida, Family Loliginidae. The strange
ball-shaped cuttlefish-like animals we see belong to Order
Sepiolida. Some small squids and cuttlefish live in the shallow
areas among the seagrasses. Others live in deeper waters and may get
trapped in a pool at low tide.
Features: From 1-2cm to about
10cm long. Compared to their more sedate cousins the slugs and snails,
squids and cuttlefishes are fast-moving predators that hunt speedy
prey like fish. They may also hunt snails and clams, crabs and prawns.
Most have a horny bird-like beak to rip up prey.
Jet-propelled molluscs: Squids
and cuttlefish squirt a jet of water out of a funnel to zoom off in
the opposite direction. They can move in any direction, but move fastest
backwards. Squids tend to be more streamlined than cuttlefish. Squids
are among the fastest aquatic invertebrates, some can reach speeds
of up to 40km/hr. A cuttlefish can also hover or swim slowly by undulating
the fins along the sides of its body. A squid does not have this all-round
fin. Instead, the fin is limited to a triangular flap at the tip of
the body, which acts as stabilisers.
Lightweight shell: Relying on
speed, squids and cuttlefish do not have a thick, heavy outer shell.
Their shells are reduced to lightweight internal bones. In squids,
the bone is thin and pencil-like. In cuttlefish, these are flat surfboards
riddled with tiny gas-filled chambers. By controlling the amount of
gas in the cuttlebone, the cuttlefish can control its bouyancy. The
cuttlebone is often seen on the beach among the flotsam. Cuttlebones
are sold in pet shops as a source of calcium for caged birds.
Armed and Dangerous: Squids and
cuttlefish have eight arms. These arms are short and stout, with suckers
along their entire length. Some have toothed suckers and hooks for
an even better grip.
In addition to the eight arms, squids and cuttlefish also have a pair
of tentacles. These may be twice as long as the arms, are thinner
and have spoon-shaped tips. Only the tips have suckers. A squid or
cuttlefish uses these two longer tentacles to grab prey. These tentacles
shoot out and retract in an eye blink, bringing the prey within the
grasp of the eight shorter arms which firmly grip the prey for the
killing bite with its sharp beak.
Disappearing Ink: When alarmed, squids
and cuttlefish may squirt a cloud of 'ink'. The ink may contain substances
that affect the senses of other sea creatures. The inky clouded water
also allows it to make a getaway. Sometimes, mucous is also released
that 'holds' the ink into a shape that distracts the predator.
Talk: Squids and cuttlefish can rapidly change colours
and patterns (zebra stripes, spots and more) to hide from predators
and prey by matching their surroundings. Cuttlefish can also change
the texture of their skin.
These colour changes are also used to communicate with each other,
for example during courtship. In some species, males and females display
different colours and patterns.
Some squids and cuttlefish also glow in the dark, producing bioluminescence.
This actually camouflages them from bottom dwelling predators which
look upwards for prey. The glowing body of a squid allows it to blend
in a moonlit sky, instead of appearing as an obvious dark shadow.
squid and cuttlefish: Some squids gather in large groups
to spawn. To mate, the male grasps the female's arms in his and inserts
his sperm packets into her body. In some, male squids scrape or flush
out sperm packets from previous suitors before inserting their own.
To prevent this, some squid sperm packets have teeth to clamp firmly
onto the female's body! The female uses the sperm to fertilise her
eggs as she lays them.
Eggs are laid in capsules, attached to hard objects and surfaces;
or inserted into crevices and other hiding places. Some cuttlefish
incorporate ink into the capsules, making them black.
Squids usually mate only once in their life and die soon after mating
and laying eggs. Cuttlefish don't produce as many eggs as squids.
Human uses: People everywhere
enjoy eating squids and cuttlefish. In Asia, they may be eaten freshly
cooked, or they may be dried. They are also made into candied snacks.
In the past, cuttlefish ink, called 'sepia', was used for writing
Squids also have a role in human medical applications. Squids have
gigantic nerve cells that are relatively easy to study. Much of what
we know about our own nervous system is based on studies of squid
nerve cells. Several Nobel prizes were based on such studies! The
squid's efficient jet propulsion system is also inspiring designs
for better underwater vehicles.
Status and threats: None of our
squids or cuttlefishes are listed among the endangered animals of
Singapore. 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 affect
A cuttlefish has fins all around its
Changi, May 05
Some squid have triangular fins
Tanah Merah, Oct 09
Other squid have broad fins
that extend the length of the body.
Pulau Semakau, Apr 08
Cephalopod Page by Dr James B Wood on the Dalhousie University
and the University of Texas Medical Branch website: everything
you could possibly want to know about cephalopods. Lots of info,
photos, articles and links to cephalopods. Lots of fabulous photos,
a delightful and exhaustive FAQ, and lots of cool articles for
the laymen. With a very cute ink-squiring squid cursor!
Cephalopods 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.
P. Ng, L. Tan, & W. Y. Chin, 1994. Rhythm of the Sea: The Life
and Times of Labrador Beach. Division of Biology, School of
Science, Nanyang Technological University & Department of Zoology,
the National University of Singapore. 160 pp.
and Peter K. L. Ng. 1994. A First Look at Biodiversity in Singapore.
National Council on the Environment. 163pp.
Ng, P. K.
L. & Y. C. Wee, 1994. The
Singapore Red Data Book: Threatened Plants and Animals of Singapore.
The Nature Society (Singapore), Singapore. 343 pp.
and Helmut Debelius, 2000. Cephalopods:
A World Guide.
ConchBooks, Germany. 319 pp
and Amanda Reid. 2000. A
Guide to Squid, Cuttlefish and Octopuses of Australasia
The Gould League of Australia. 96pp.