Snails build their shells by using the calcium present in water. As their bodies grow, more calcium is added to the open end of the shell to make it bigger.
Many snails have a locking system on their bodies. A tough disc, called an operculum is present on their foot. Whenever the snail desires, it can pull the operculum up to block the opening of its shell and protect its soft body.
Snails do not have hands but they are often called left-handed or right-handed. Most snails coil in a clockwise direction. These are right-handed. Those that coil anti-clockwise are left-handed.
Cone shells are among the most beautiful shells in the world but the animals inside them are deadly. They shoot a poison dart into their prey to paralyse it. The poison is sometimes strong enough to kill a human being.
Glory of India8217;, a brilliantly-coloured cone is very rare. Only 150 specimens are found worldwide.
The Giant Clam, found in the Indian subcontinent, is the biggest mollusc in the world. It can grow up to six feet in length and can weigh more than two adult humans. The shell of this clam is used to make exotic bath tubs. For that reason the animal inside is killed.
When a foreign body such as a sand grain enters a pearl oyster, the animal secretes a shiny fluid to cover it. Then it expels it out of the body. This process turns the stone into a pearl. In pearl farming, sand grains are artificially inserted inside the oyster to cause pearl formation.
Sea slugs may lack shells but they are related to snails. They are protected by their nasty taste and their bright colours warn enemies that they are not good to eat.
One sea slug, an egg-eating Calma, has strange feeding habits. This slug drills holes in fish eggs and sucks out their contents. It feeds only once a year 8212; during the egg-laying season of fish. Calma is common to the Great Barrier Reef of Australia and is not found in India.
An octopus has no shell but it is, still, a mollusc. It can change colour to match its background, in seconds, so that it can hide almost anywhere.
Cowries, marble-like glossy shells, were used by Arab traders and tribes in West Africa in ancient times as money8217;!
