A
Beginner's Introduction to Molluscs
By Sammy Snail
Hello, my name is Sammy Snail and I am a mollusc. The name "mollusc" is derived from the Latin word "mollis" which means soft. (Latin is the language scientists use to talk about things in nature.) My body is soft. I do not have a backbone, or any other bones for that matter. My skeleton is in fact my shell - and some of my cousins don't even have a shell! Scientists classify me as an invertebrate, which is just a big name for a group of animals without backbones.
Some of my ancestors first appeared on this earth about 600 million years ago. We are able to see what they looked like, or at least what their shell homes looked like, from their fossil records. To compare, man has only been on this earth about 2 million years.
Scientists who study molluscs are called conchologists or malacologists. Scientists group all plants and animals into specific categories according to their common body features. These features may include such things as where they live, what they eat and how their bodies are made and work. Conchologists grouped us molluscs together because of the following common features we share.
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1. Like me, most of my relatives have a shell. This is a hard home that we build to house and protect our soft bodies. Not all of us have a shell though.
2.
We all have a fleshy mantle. This is a flesh-like
lobe or pair of lobes that produce our shell.
3. We
have a radula. This is our teeth. Our radula resembles a fingernail
file or the chain on a chain saw. We rasp our food with this rough ribbon
of teeth just like a cat licks up his food with his rough tongue. Our radula
is located in our mouth just like your teeth are in your mouth. (Billy
Bivalve and his relatives the bivalves don t have this radula. Billy
will tell you about his family a little later.) 4.
We all have a muscular foot. We use our foot to
move around on or some use it to dig into the sand or mud where they live.
Some of our relatives use this foot to cling onto hard rocky surfaces.
They can hang on so tightly, that you cannot pull them off. In some of
our other relatives, like the squid and octopus, their foot has evolved
(changed over thousands of years) to become many arms or tentacles. 5.
We all have to keep our soft bodies moist
to stay alive
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My mollusc relatives have learned to survive in almost all
the areas of the world. The aquatic molluscs live in water. They live in the
salty oceans from the
intertidal areas (that area where waves and tides wash
in and out) to the deepest parts, called trenches. Many live in fresh water
areas such as lakes and streams. The terrestrial molluscs
live on land. This is where my closest relatives and I live. (Maybe
you have seen one of my cousins in your own back yard.) Some,
like me, live under rotting leaves or logs. Others live high up in the trees.
Some live on mountains, others in deserts. So you see, we have adapted rather
well to living here on earth.
Some
of my mollusc relatives have even evolved to become molluscs without a shell.
They too, live in the oceans and on land. You may know some of these shells
land cousins of mine as the slugs and the ones living
in the oceans as sea butterflies or sea slugs (they are
very beautiful: for many pictures of these lovely creatures, see the Flat Worms of the World
site).
Scientists have taken our large group (known as a Phylum),
the molluscs, and have divided us into seven classes.
Molluscs within each Class have body features that are similar to each other.
This class is then further divided into families once again according to their
similarities.
I will now have some of my cousins introduce themselves to
you and have them tell you a bit about their class and who some of their family
members are.
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I am happy to introduce you to: Andrew I
hope you enjoy their talks |