THE VARIED ROLES OF SNAILS - National Universities Commission

Most bivalves reproduce by laying millions of eggs into the
water surrounding us. The male bivalves then release their
sperm into the same water. If the eggs and sperm meet, a
new baby bivalve is born. However, some species hold
their eggs in a space called the mantle cavity in their body.
The males still spurt their sperm into the water and when
she pulls this water in through her siphon, the eggs are
fertilized. These are then brooded inside her body until she
knows they are big enough to live in the water. She then
releases them into the water. All juvenile bivalves start life
as tiny specks, (larval stage) swimming in the water. When
these larvae become big enough, they start to settle in their
new homes. When they are still young, and settled, they are
called “spat”.
Some molluscs, such as the oysters, change sex. Some like
oysters even alternate their gender. Male one year, female
the next year,
Some bivalves like to live attached to hard objects such as
rocks or manmade objects. Some live all their lives buried
beneath the sandy or muddy ocean, lake or stream bottoms.
Some actually live inside wood. These bivalves (known as
ship worms) have caused man a lot of trouble when he sails
in wooden ships. for example the Barnacles make holes on
the ship body. They also attack wharves and other wooden
man made structures causing a lot of damages. Some of the
other species are parasites, meaning that they live inside a
living host.
2. WHAT ARE ACTUALLY THE SNAILS?
The scientific classification of snails shows that they
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