While most people will find other invertebrates boring, almost no one can resist a mollusc. 'Mollis' means 'soft bodies'. There are about 50,000 species of molluscs. Delicious! For a start, molluscs are among our favourite seafood! Snails and clams have also attractive shells. Octopus are among the smartest invertebrates, and among the most beautiful creatures on Chek Jawa are nudibranchs! Different! Molluscs are one of the largest animal Phyla. With such a large assembly under one group, not surprisingly, there isn't really such a thing as a 'typical' mollusc. Generalisations are difficult to make for this large and diverse Phylum. Soft and squishy: Among the few features shared by all molluscs is a soft body. To protect this soft body, snails produce a shell, while clams produce a pair of shells. Slugs which lack shells often have toxins and other defences. Others like squids and cuttlefish rely on speed instead. Big Foot: In many molluscs, a large foot makes up much of the body. The foot has cells that produce mucous to help them move over a surface. The foot is often radically modified in some members such as octopuses and squids. Terrible Tongue: Most molluscs also have a radula; a firm ribbon-like structure made of protein-chitin, covered with sharp teeth made of chitin. The radula is usually used for feeding and can modified in amazing ways to rasp, grate, grasp, cut, stab and inject poison. For example, drills are snails that use their radula to make a hole through their hard-shelled prey. Here are diagrams of how a grazing snail uses its radula to feed on algae. Some fabulous close-up photos of what a radula looks like are on the Archerd Shell Collection website. Other Features: Many molluscs also have tentacles, a pair of eyes and a pair of balance organs. Most also have an osphradia, a sensory patch inside the body that is believed to process chemicals in the water flowing into the body. Most molluscs have gills. These are often inside a chamber in the body called a mantle cavity. Most also have a circulatory system and a heart, as well as kidneys. Mollusc Babies: Most molluscs have separate genders. The details of the way each group reproduces is covered in the sections on them. Human uses: Molluscs have been exploited by humans for millenia. Uses range from food to adornments (dyes, shells, pearls) to even money (cowrie shells). Molluscs continue to play some of these roles today. In addition, some molluscs are being studied for modern medical applications. For example, the toxins of the highly venomous cone shells (Family Conidae) are being studied for applications in pain control. Status and threats: Like other marine creatures, molluscs are vulnerable to habitat loss due to reclamation or human activities along the coast that pollute the water. They are also vulnerable to over-collection for food and for their shells.

Nudibranch Whelk Sea hare Squid Limpet Cowrie

• Barnes, Robert D. & Ruppert, Edward E., 1996. Invertebrate Zoology. Harcourt College Publishers. 6th Edition. pp. 1056, G-1-16, I-1-30.
• Pechenik, Jan A., 2000. Biology of the Invertebrates. McGraw-Hill Book Co., Singapore. 578 pp.

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