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Squid and cuttlefish Class Cephalopoda

Cuttlefish

Squids and cuttlefish come to the seagrass lagoon of Chek Jawa to feed, breed and lay their eggs. Tiny ones are sometimes seen among the seagrasses. Sometimes, adults get trapped in a pool at low tide.

Squids and cuttlefish are molluscs! Unlike 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. They are more active at night.

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.

Squid	Armed and Dangerous: Squids and cuttlefish have ten arms. Eight of the arms are short and stout, with suckers along their length. Some have toothed suckers and hooks for an even better grip. The other two are called tentacles and may be twice as long as the arms. These are thinner and with spoon-shaped tips. Only the tips have suckers.
Cuttlefish snatching prey with its tentacles

A squid or cuttlefish uses its two longer tentacles to grab prey. These 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 squirt a cloud of 'ink' that distracts predators and clouds up the water.

Colourful Talk: Squids and cuttlefish can rapidly change colours to hide from predators and prey by matching their surroundings.

Cuttlefish can also change the texture of their skin. They also use colour changes to communicate with each other in courtship.

In some species, males and females display different colours and patterns.

This cuttlefish changed into various
colours and patterns in an instant!

Baby 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. Here is a fascinating photo of a baby squid on Image Quest 3-D Marine Library

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. 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! In the past, cuttlefish ink, called 'sepia', was used for writing and painting.

Cuttlefish

Tiny squid

Cuttlefish bone

Cuttlefish
egg capsules

The black capsules are transparent after the babies hatch

Here's a rare view of the babies inside the capsules just before they emerge!

quick facts
To about 20cm long, but tiny ones 1-2cm also sometimes seen in the seagrass lagoon.

Classification:
Class Cephalopoda
Phylum Mollusca

See also ...
Molluscs in general
Cephalopods in general
Octopuses are also cephalopods

Links
The 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!
Cephbase by Dr James B Wood: has more detailed information on species
Class Cephalopoda on Biomedia of the Glasgow University Zoological Museum on the Biological Sciences, University of Paisley, Scotland website: a brief introduction with explanations of the major classes, a glossary of terms and diagrams and photos.
Curious about cuttlebones by Shirley Slack-Smith on the Beachcomber on the Western Fisheries Magazine: about cuttlefish and their bones
Incredible Suckers on the Public Broadcasting Service (PBS) website: about cephalopods in general and the search for Giant Squid. Lots of photos and links.
Cuttlefish on EnchantedLearning.com: fact sheet with labelled diagram of cuttlefish parts.
Squid on EnchantedLearning.com: fact sheet with labelled diagram of squid parts.
National Resource Center for Cephalopods: fact sheets on how squids are used in scientific research, e.g., study of nerve cells.
Long-finned Squid: its role in understanding biology from the Marine Biological Laboratory, Woods Hole website: about the contributions of this squid to our understanding of the human nervous system.
New Creature from the Deep on the ScienceNow page of the California Academy of Sciences website: about the discovery of a new giant squid, with photos and links.
How do squids swim using their siphons as jets? on the Mad Scientist website: Alastair Lyon gives a simple explanation.

Other references

Tan, Leo W. H. & Ng, Peter K. L., 1988, A Guide to Seashore Life. The Singapore Science Centre, Singapore. 160 pp. online version
Lim, S., 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.
Norman, Mark., 2000. Cephalopods: A World Guide. ConchBooks, Germany. 319 pp.
Ong, Jin Eong & Gong, Wooi Khoon (eds.), 2001. The Encyclopedia of Malaysia (Vol. 6): The Seas. Didier Millet, Malaysia. 144 pp.

a companion website to the chek jawa guidebook website©ria tan 2003 www.wildsingapore.com

a companion website to the chek jawa guidebook
website©ria tan 2003 www.wildsingapore.com